blk_throtl_dispatch_work_fn is only used in blk-throttle.c
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Jens Axboe <axboe@fb.com>
cftype->write_string() just passes on the writeable buffer from kernfs
and there's no reason to add const restriction on the buffer. The
only thing const achieves is unnecessarily complicating parsing of the
buffer. Drop const from @buffer.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
cftype->max_write_len is used to extend the maximum size of writes.
It's interpreted in such a way that the actual maximum size is one
less than the specified value. The default size is defined by
CGROUP_LOCAL_BUFFER_SIZE. Its interpretation is quite confusing - its
value is decremented by 1 and then compared for equality with max
size, which means that the actual default size is
CGROUP_LOCAL_BUFFER_SIZE - 2, which is 62 chars.
There's no point in having a limit that low. Update its definition so
that it means the actual string length sans termination and anything
below PAGE_SIZE-1 is treated as PAGE_SIZE-1.
.max_write_len for "release_agent" is updated to PATH_MAX-1 and
cgroup_release_agent_write() is updated so that the redundant strlen()
check is removed and it uses strlcpy() instead of strcpy().
.max_write_len initializations in blk-throttle.c and cfq-iosched.c are
no longer necessary and removed. The one in cpuset is kept unchanged
as it's an approximated value to begin with.
This will also make transition to kernfs smoother.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Pull core block IO changes from Jens Axboe:
"The major piece in here is the immutable bio_ve series from Kent, the
rest is fairly minor. It was supposed to go in last round, but
various issues pushed it to this release instead. The pull request
contains:
- Various smaller blk-mq fixes from different folks. Nothing major
here, just minor fixes and cleanups.
- Fix for a memory leak in the error path in the block ioctl code
from Christian Engelmayer.
- Header export fix from CaiZhiyong.
- Finally the immutable biovec changes from Kent Overstreet. This
enables some nice future work on making arbitrarily sized bios
possible, and splitting more efficient. Related fixes to immutable
bio_vecs:
- dm-cache immutable fixup from Mike Snitzer.
- btrfs immutable fixup from Muthu Kumar.
- bio-integrity fix from Nic Bellinger, which is also going to stable"
* 'for-3.14/core' of git://git.kernel.dk/linux-block: (44 commits)
xtensa: fixup simdisk driver to work with immutable bio_vecs
block/blk-mq-cpu.c: use hotcpu_notifier()
blk-mq: for_each_* macro correctness
block: Fix memory leak in rw_copy_check_uvector() handling
bio-integrity: Fix bio_integrity_verify segment start bug
block: remove unrelated header files and export symbol
blk-mq: uses page->list incorrectly
blk-mq: use __smp_call_function_single directly
btrfs: fix missing increment of bi_remaining
Revert "block: Warn and free bio if bi_end_io is not set"
block: Warn and free bio if bi_end_io is not set
blk-mq: fix initializing request's start time
block: blk-mq: don't export blk_mq_free_queue()
block: blk-mq: make blk_sync_queue support mq
block: blk-mq: support draining mq queue
dm cache: increment bi_remaining when bi_end_io is restored
block: fixup for generic bio chaining
block: Really silence spurious compiler warnings
block: Silence spurious compiler warnings
block: Kill bio_pair_split()
...
In preparation of conversion to kernfs, cgroup file handling is
updated so that it can be easily mapped to kernfs. This patch
replaces cftype->read_seq_string() with cftype->seq_show() which is
not limited to single_open() operation and will map directcly to
kernfs seq_file interface.
The conversions are mechanical. As ->seq_show() doesn't have @css and
@cft, the functions which make use of them are converted to use
seq_css() and seq_cft() respectively. In several occassions, e.f. if
it has seq_string in its name, the function name is updated to fit the
new method better.
This patch does not introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Aristeu Rozanski <arozansk@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Now that seqcounts are lockdep enabled objects, we need to explicitly
initialize runtime allocated seqcounts so that lockdep can track them.
Without this patch, Fengguang was seeing:
[ 4.127282] INFO: trying to register non-static key.
[ 4.128027] the code is fine but needs lockdep annotation.
[ 4.128027] turning off the locking correctness validator.
[ 4.128027] CPU: 0 PID: 96 Comm: kworker/u4:1 Not tainted 3.12.0-next-20131108-10601-gbad570d #2
[ 4.128027] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ ... ]
[ 4.128027] Call Trace:
[ 4.128027] [<7908e744>] ? console_unlock+0x353/0x380
[ 4.128027] [<79dc7cf2>] dump_stack+0x48/0x60
[ 4.128027] [<7908953e>] __lock_acquire.isra.26+0x7e3/0xceb
[ 4.128027] [<7908a1c5>] lock_acquire+0x71/0x9a
[ 4.128027] [<794079aa>] ? blk_throtl_bio+0x1c3/0x485
[ 4.128027] [<7940658b>] throtl_update_dispatch_stats+0x7c/0x153
[ 4.128027] [<794079aa>] ? blk_throtl_bio+0x1c3/0x485
[ 4.128027] [<794079aa>] blk_throtl_bio+0x1c3/0x485
...
Use u64_stats_init() for all affected data structures, which initializes
the seqcount.
Reported-and-Tested-by: Fengguang Wu <fengguang.wu@intel.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
[ Folded in another fix from the mailing list as well as a fix to that fix. Tweaked commit message. ]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1384314134-6895-1-git-send-email-john.stultz@linaro.org
[ So I actually think that the two SOBs from PeterZ are the right depiction of the patch route. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Previously, all css descendant iterators didn't include the origin
(root of subtree) css in the iteration. The reasons were maintaining
consistency with css_for_each_child() and that at the time of
introduction more use cases needed skipping the origin anyway;
however, given that css_is_descendant() considers self to be a
descendant, omitting the origin css has become more confusing and
looking at the accumulated use cases rather clearly indicates that
including origin would result in simpler code overall.
While this is a change which can easily lead to subtle bugs, cgroup
API including the iterators has recently gone through major
restructuring and no out-of-tree changes will be applicable without
adjustments making this a relatively acceptable opportunity for this
type of change.
The conversions are mostly straight-forward. If the iteration block
had explicit origin handling before or after, it's moved inside the
iteration. If not, if (pos == origin) continue; is added. Some
conversions add extra reference get/put around origin handling by
consolidating origin handling and the rest. While the extra ref
operations aren't strictly necessary, this shouldn't cause any
noticeable difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
cgroup is currently in the process of transitioning to using css
(cgroup_subsys_state) as the primary handle instead of cgroup in
subsystem API. For hierarchy iterators, this is beneficial because
* In most cases, css is the only thing subsystems care about anyway.
* On the planned unified hierarchy, iterations for different
subsystems will need to skip over different subtrees of the
hierarchy depending on which subsystems are enabled on each cgroup.
Passing around css makes it unnecessary to explicitly specify the
subsystem in question as css is intersection between cgroup and
subsystem
* For the planned unified hierarchy, css's would need to be created
and destroyed dynamically independent from cgroup hierarchy. Having
cgroup core manage css iteration makes enforcing deref rules a lot
easier.
Most subsystem conversions are straight-forward. Noteworthy changes
are
* blkio: cgroup_to_blkcg() is no longer used. Removed.
* freezer: cgroup_freezer() is no longer used. Removed.
* devices: cgroup_to_devcgroup() is no longer used. Removed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Jens Axboe <axboe@kernel.dk>
cgroup is currently in the process of transitioning to using struct
cgroup_subsys_state * as the primary handle instead of struct cgroup.
Please see the previous commit which converts the subsystem methods
for rationale.
This patch converts all cftype file operations to take @css instead of
@cgroup. cftypes for the cgroup core files don't have their subsytem
pointer set. These will automatically use the dummy_css added by the
previous patch and can be converted the same way.
Most subsystem conversions are straight forwards but there are some
interesting ones.
* freezer: update_if_frozen() is also converted to take @css instead
of @cgroup for consistency. This will make the code look simpler
too once iterators are converted to use css.
* memory/vmpressure: mem_cgroup_from_css() needs to be exported to
vmpressure while mem_cgroup_from_cont() can be made static.
Updated accordingly.
* cpu: cgroup_tg() doesn't have any user left. Removed.
* cpuacct: cgroup_ca() doesn't have any user left. Removed.
* hugetlb: hugetlb_cgroup_form_cgroup() doesn't have any user left.
Removed.
* net_cls: cgrp_cls_state() doesn't have any user left. Removed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Steven Rostedt <rostedt@goodmis.org>
With the recent updates, blk-throttle is finally ready for proper
hierarchy support. Dispatching now honors service_queue->parent_sq
and propagates correctly. The only thing missing is setting
->parent_sq correctly so that throtl_grp hierarchy matches the cgroup
hierarchy.
This patch updates throtl_pd_init() such that service_queues form the
same hierarchy as the cgroup hierarchy if sane_behavior is enabled.
As this concludes proper hierarchy support for blkcg, the shameful
.broken_hierarchy tag is removed from blkio_subsys.
v2: Updated blkio-controller.txt as suggested by Vivek.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Li Zefan <lizefan@huawei.com>
blk_throtl_bio() has a quick exit path for throtl_grps without limits
configured. It looks at the bps and iops limits and if both are not
configured, the bio is issued immediately. While this is correct in
the current flat hierarchy as each throtl_grp behaves completely
independently, it would become wrong in proper hierarchy mode. A
group without any limits could still be limited by one of its
ancestors and bio's queued for such group should not bypass
blk-throtl.
As having a quick bypass mechanism is beneficial, this patch
reimplements the mechanism such that it's correct even with proper
hierarchy. throtl_grp->has_rules[] is added. These booleans are
updated for the whole subtree whenever a config is updated so that
has_rules[] of the whole subtree stays synchronized. They're also
updated when a new throtl_grp comes online so that it can't escape the
limits of its ancestors.
As no throtl_grp has another throtl_grp as parent now, this patch
doesn't yet make any behavior differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
With the planned proper hierarchy support, a bio will climb up the
tree before actually being dispatched. This makes sure bio is also
subjected to parent's throttling limits, if any.
It might happen that parent is idle and when bio is transferred to
parent, a new slice starts fresh. But that is incorrect as parents
wait time should have started when bio was queued in child group and
causes IOs to be throttled more than configured as they climb the
hierarchy.
Given the fact that we have not written hierarchical algorithm in a
way where child's and parents time slices are synchronized, we
transfer the child's start time to parent if parent was idling. If
parent was busy doing dispatch of other bios all this while, this is
not an issue.
Child's slice start time is passed to parent. Parent looks at its
last expired slice start time. If child's start time is after parents
old start time, that means parent had been idle and after parent
went idle, child had an IO queued. So use child's start time as
parent start time.
If parent's start time is after child's start time, that means,
when IO got queued in child group, parent was not idle. But later
it dispatched some IO, its slice got trimmed and then it went idle.
After a while child's request got shifted in parent group. In this
case use parent's old start time as new start time as that's the
duration of slice we did not use.
This logic is far from perfect as if there are multiple childs
then first child transferring the bio decides the start time while
a bio might have queued up even earlier in other child, which is
yet to be transferred up to parent. In that case we will lose
time and bandwidth in parent. This patch is just an approximation
to make situation somewhat better.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
With flat hierarchy, there's only single level of dispatching
happening and fairness beyond that point is the responsibility of the
rest of the block layer and driver, which usually works out okay;
however, with the planned hierarchy support,
service_queue->bio_lists[] can be filled up by bios from a single
source. While the limits would still be honored, it'd be very easy to
starve IOs from siblings or children.
To avoid such starvation, this patch implements throtl_qnode and
converts service_queue->bio_lists[] to lists of per-source qnodes
which in turn contains the bio's. For example, when a bio is
dispatched from a child group, the bio doesn't get queued on
->bio_lists[] directly but it first gets queued on the group's qnode
which in turn gets queued on service_queue->queued[]. When
dispatching for the upper level, the ->queued[] list is consumed in
round-robing order so that the dispatch windows is consumed fairly by
all IO sources.
There are two ways a bio can come to a throtl_grp - directly queued to
the group or dispatched from a child. For the former
throtl_grp->qnode_on_self[rw] is used. For the latter, the child's
->qnode_on_parent[rw].
Note that this means that the child which is contributing a bio to its
parent should stay pinned until all its bios are dispatched to its
grand-parent. This patch moves blkg refcnting from bio add/remove
spots to qnode activation/deactivation so that the blkg containing an
active qnode is always pinned. As child pins the parent, this is
sufficient for keeping the relevant sub-tree pinned while bios are in
flight.
The starvation issue was spotted by Vivek Goyal.
v2: The original patch used the same throtl_grp->qnode_on_self/parent
for reads and writes causing RWs to be queued incorrectly if there
already are outstanding IOs in the other direction. They should
be throtl_grp->qnode_on_self/parent[2] so that READs and WRITEs
can use different qnodes. Spotted by Vivek Goyal.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
throtl_pending_timer_fn() currently assumes that the parent_sq is the
top level one and the bio's dispatched are ready to be issued;
however, this assumption will be wrong with proper hierarchy support.
This patch makes the following changes to make
throtl_pending_timer_fn() ready for hiearchy.
* If the parent_sq isn't the top-level one, update the parent
throtl_grp's dispatch time and schedule the next dispatch as
necessary. If the parent's dispatch time is now, repeat the
function for the parent throtl_grp.
* If the parent_sq is the top-level one, kick issue work_item as
before.
* The debug message printed by throtl_log() now prints out the
service_queue's nr_queued[] instead of the total nr_queued as the
latter becomes uninteresting and misleading with hierarchical
dispatch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
tg_dispatch_one_bio() currently assumes that the parent_sq is the top
level one and the bio being dispatched is ready to be issued; however,
this assumption will be wrong with proper hierarchy support. This
patch makes the following changes to make tg_dispatch_on_bio() ready
for hiearchy.
* throtl_data->nr_queued[] is incremented in blk_throtl_bio() instead
of throtl_add_bio_tg() so that throtl_add_bio_tg() can be used to
transfer a bio from a child tg to its parent.
* tg_dispatch_one_bio() is updated to distinguish whether its parent
is another throtl_grp or the throtl_data. If former, the bio is
transferred to the parent throtl_grp using throtl_add_bio_tg(). If
latter, the bio is ready to be issued and put on the top-level
service_queue's bio_lists[] and throtl_data->nr_queued is
decremented.
As all throtl_grps currently have the top level service_queue as their
->parent_sq, this patch in itself doesn't make any behavior
difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Currently, blk_throtl_bio() issues the passed in bio directly if it's
within limits of its associated tg (throtl_grp). This behavior
becomes incorrect with hierarchy support as the bio should be
accounted to and throttled by the ancestor throtl_grps too.
This patch makes the direct issue path of blk_throtl_bio() to loop
until it reaches the top-level service_queue or gets throttled. If
the former, the bio can be issued directly; otherwise, it gets queued
at the first layer it was above limits.
As tg->parent_sq is always the top-level service queue currently, this
patch in itself doesn't make any behavior differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
The current blk_throtl_drain() assumes that all active throtl_grps are
queued on throtl_data->service_queue, which won't be true once
hierarchy support is implemented.
This patch makes blk_throtl_drain() perform post-order walk of the
blkg hierarchy draining each associated throtl_grp, which guarantees
that all bios will eventually be pushed to the top-level service_queue
in throtl_data.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Currently, blk_throtl_dispatch_work_fn() is responsible for both
dispatching bio's from throtl_grp's according to their limits and then
issuing the dispatched bios.
This patch moves the dispatch part to throtl_pending_timer_fn() so
that the work item is kicked iff there are bio's to issue. This is to
avoid work item execution at each step when hierarchy support is
enabled. bio's will be dispatched towards the top-level service_queue
from the timers at each layer and the work item will only be used to
issue the bio's which reached the top-level service_queue.
While fetching bio's to issue from bio_lists[],
blk_throtl_dispatch_work_fn() fetches all READs before WRITEs. While
the original code also dispatched READs first, if multiple throtl_grps
are dispatched on the same run, WRITEs from throtl_grp which is
dispatched first would precede READs from throtl_grps which are
dispatched later. While this is a behavior change, given that the
previous code already prioritized READs and block layer generally
prioritizes and segregates READs from WRITEs, this isn't likely to
make any noticeable differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
throtl_select_dispatch() only dispatches throtl_quantum bios on each
invocation. blk_throtl_dispatch_work_fn() in turn depends on
throtl_schedule_next_dispatch() scheduling the next dispatch window
immediately so that undue delays aren't incurred. This effectively
chains multiple dispatch work item executions back-to-back when there
are more than throtl_quantum bios to dispatch on a given tick.
There is no reason to finish the current work item just to repeat it
immediately. This patch makes throtl_schedule_next_dispatch() return
%false without doing anything if the current dispatch window is still
open and updates blk_throtl_dispatch_work_fn() repeat dispatching
after cpu_relax() on %false return.
This change will help implementing hierarchy support as dispatching
will be done from pending_timer and immediate reschedule of timer
function isn't supported and doesn't make much sense.
While this patch changes how dispatch behaves when there are more than
throtl_quantum bios to dispatch on a single tick, the behavior change
is immaterial.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Currently, throtl_data->dispatch_work is a delayed_work item which
handles both delayed dispatch and issuing bios. The two tasks will be
separated to support proper hierarchy. To prepare for that, this
patch separates out the timer into throtl_service_queue->pending_timer
from throtl_data->dispatch_work and make the latter a work_struct.
* As the timer is now per-service_queue, it's initialized and
del_sync'd as its corresponding service_queue is created and
destroyed. The timer, when triggered, simply schedules
throtl_data->dispathc_work for execution.
* throtl_schedule_delayed_work() is renamed to
throtl_schedule_pending_timer() and takes @sq and @expires now.
* Simiarly, throtl_schedule_next_dispatch() now takes @sq, which
should be the parent_sq of the service_queue which just got a new
bio or updated. As the parent_sq is always the top-level
service_queue now, this doesn't change anything at this point.
This patch doesn't introduce any behavior differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
With proper hierarchy support, a bio can be dispatched multiple times
until it reaches the top-level service_queue and we don't want to
update dispatch stats at each step. They are local stats and will be
kept local. If recursive stats are necessary, they should be
implemented separately and definitely not by updating counters
recursively on each dispatch.
This patch moves REQ_THROTTLED setting to throtl_charge_bio() and gate
stats update with it so that dispatch stats are updated only on the
first time the bio is charged to a throtl_grp, which will always be
the throtl_grp the bio was originally queued to.
This means that REQ_THROTTLED would be set even for bios which don't
get throttled. As we don't want bios to leave blk-throtl with the
flag set, move REQ_THROTLLED clearing to the end of blk_throtl_bio()
and clear if the bio is being issued directly.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Now that both throtl_data and throtl_grp embed throtl_service_queue,
we can unify throtl_log() and throtl_log_tg().
* sq_to_tg() is added. This returns the throtl_grp a service_queue is
embedded in. If the service_queue is the top-level one embedded in
throtl_data, NULL is returned.
* sq_to_td() is added. A service_queue is always associated with a
throtl_data. This function finds the associated td and returns it.
* throtl_log() is updated to take throtl_service_queue instead of
throtl_data. If the service_queue is one embedded in throtl_grp, it
prints the same header as throtl_log_tg() did. If it's one embedded
in throtl_data, it behaves the same as before. This renders
throtl_log_tg() unnecessary. Removed.
This change is necessary for hierarchy support as we're gonna be using
the same code paths to dispatch bios to intermediate service_queues
embedded in throtl_grps and the top-level service_queue embedded in
throtl_data.
This patch doesn't make any behavior changes.
v2: throtl_log() didn't print a space after blkg path. Updated so
that it prints a space after throtl_grp path. Spotted by Vivek.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
To prepare for hierarchy support, this patch adds
throtl_service_queue->service_sq which points to the arent
service_queue. Currently, for all service_queues embedded in
throtl_grps, it points to throtl_data->service_queue. As
throtl_data->service_queue doesn't have a parent its parent_sq is set
to NULL.
There are a number of functions which take both throtl_grp *tg and
throtl_service_queue *parent_sq. With this patch, the parent
service_queue can be determined from @tg and the @parent_sq arguments
are removed.
This patch doesn't make any behavior differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
When blk_throtl_bio() wants to queue a bio to a tg (throtl_grp), it
avoids invoking tg_update_disptime() and
throtl_schedule_next_dispatch() if the tg already has bios queued in
that direction. As a new bio is appeneded after the existing ones, it
can't change the tg's next dispatch time or the parent's dispatch
schedule.
This optimization is currently open coded in blk_throtl_bio().
Whether the target biolist was occupied was recorded in a local
variable and later used to skip disptime update. This patch moves
generalizes it so that throtl_add_bio_tg() sets a new flag
THROTL_TG_WAS_EMPTY if the biolist was empty before the new bio was
added. tg_update_disptime() clears the flag automatically.
blk_throtl_bio() is updated to simply test the flag before updating
disptime.
This patch doesn't make any functional differences now but will enable
using the same optimization for recursive dispatch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
throtl_service_queues will eventually form a tree which is anchored at
throtl_data->service_queue and queue bios will climb the tree to the
top service_queue to be executed.
This patch makes the dispatch paths in blk_throtl_dispatch_work_fn()
and blk_throtl_drain() to dispatch bios to
throtl_data->service_queue.bio_lists[] instead of the on-stack
bio_lists. This will keep the final dispatch to the top level
service_queue share the same mechanism as dispatches through the rest
of the hierarchy.
As bio's should be issued in a sleepable context,
blk_throtl_dispatch_work_fn() transfers all dispatched bio's from the
service_queue bio_lists[] into an onstack one before dropping
queue_lock and issuing the bio's.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
throtl_service_queues will eventually form a tree which is anchored at
throtl_data->service_queue and queue bios will climb the tree to the
top service_queue to be executed.
This patch moves bio_lists[] and nr_queued[] from throtl_grp to its
service_queue to prepare for that. As currently only the
throtl_data->service_queue is in use, this patch just ends up moving
throtl_grp->bio_lists[] and ->nr_queued[] to
throtl_grp->service_queue.bio_lists[] and ->nr_queued[] without making
any functional differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Currently, there's single service_queue per queue -
throtl_data->service_queue. All active throtl_grp's are queued on the
queue and dispatched according to their limits. To support hierarchy,
this will be expanded such that active throtl_grp's form a tree
anchored at throtl_data->service_queue and chained through each
intermediate throtl_grp's service_queue.
This patch adds throtl_grp->service_queue to prepare for hierarchy
support. The initialization function - throtl_service_queue_init() -
is added and replaces the macro initializer. The newly added
tg->service_queue isn't used yet. Following patches will do.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
throtl_service_queue will be the building block of hierarchy support
and will form a tree. This patch updates its usages as arguments to
reduce confusion.
* When a service queue is used as the parent role - the host of the
rbtree - use @parent_sq instead of @sq.
* For functions taking both @tg and @parent_sq, reorder them so that
the order is (@tg, @parent_sq) not the other way around. This makes
the code follow the usual convention of specifying the primary
target of the operation as the first argument.
This patch doesn't make any functional differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
throtl_service_queue will be used as the basic block to implement
hierarchy support. Pass around throtl_service_queue *sq instead of
throtl_data *td in the following functions which will be used across
multiple levels of hierarchy.
* [__]throtl_enqueue/dequeue_tg()
* throtl_add_bio_tg()
* tg_update_disptime()
* throtl_select_dispatch()
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Add throtl_grp->td so that the td (throtl_data) a given tg
(throtl_grp) belongs to can be determined, and remove @td argument
from functions which take both @td and @tg as the former now can be
determined from the latter.
This generally simplifies the code and removes a number of cases where
@td is passed as an argument without being actually used. This will
also help hierarchy support implementation.
While at it, in multi-line conditions, move the logical operators
leading broken lines to the end of the previous line.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
blk-throttle is still using function-defining macros to define flag
handling functions, which went out style at least a decade ago.
Just define the flag as bitmask and use direct bit operations.
This patch doesn't make any functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
throtl_rb_root will be expanded to cover more roles for hierarchy
support. Rename it to throtl_service_queue and make its fields more
descriptive.
* rb -> pending_tree
* left -> first_pending
* count -> nr_pending
* min_disptime -> first_pending_disptime
This patch is purely cosmetic.
Signed-off-by: Tejun Heo <tj@kernel.org
Acked-by: Vivek Goyal <vgoyal@redhat.com>
throtl_nr_queued() is used in several places to avoid performing
certain operations when the throtl_data is empty. This usually is
useless as those paths usually aren't traveled if there's no bio
queued.
* throtl_schedule_delayed_work() skips scheduling dispatch work item
if @td doesn't have any bios queued; however, the only case it can
be called when @td is empty is from tg_set_conf() which isn't
something we should be optimizing for.
* throtl_schedule_next_dispatch() takes a quick exit if @td is empty;
however, right after that it triggers BUG if the service tree is
empty. The two conditions are equivalent and it can just test
@st->count for the quick exit.
* blk_throtl_dispatch_work_fn() skips dispatch if @td is empty. This
work function isn't usually invoked when @td is empty. The only
possibility is from tg_set_conf() and when it happens the normal
dispatching path can handle empty @td fine. No need to add special
skip path.
This patch removes the above three unnecessary optimizations, which
leave throtl_log() call in blk_throtl_dispatch_work_fn() the only user
of throtl_nr_queued(). Remove throtl_nr_queued() and open code it in
throtl_log(). I don't think we need td->nr_queued[] at all. Maybe we
can remove it later.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Move throtl_schedule_delayed_work() above its first user so that the
forward declaration can be removed.
This patch is pure relocaiton.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
blk-throttle is about to go through major restructuring to support
hierarchy. Do cosmetic updates in preparation.
* s/throtl_data->throtl_work/throtl_data->dispatch_work/
* s/blk_throtl_work()/blk_throtl_dispatch_work_fn()/
* Collapse throtl_dispatch() into blk_throtl_dispatch_work_fn()
This patch is purely cosmetic.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
When bps or iops configuration changes, blk-throttle records the new
configuration and sets a flag indicating that the config has changed.
The flag is checked in the bio dispatch path and applied. This
deferred config application was necessary due to limitations in blkcg
framework, which haven't existed for quite a while now.
This patch removes the deferred config application mechanism and
applies new configurations directly from tg_set_conf(), which is
simpler.
v2: Dropped unnecessary throtl_schedule_delayed_work() call from
tg_set_conf() as suggested by Vivek Goyal.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
throtl_select_dispatch() calls throtl_enqueue_tg() right after
tg_update_disptime(), which always calls the function anyway. The
call is, while harmless, unnecessary. Remove it.
This patch doesn't introduce any behavior difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
QUEUE_FLAG_DEAD is used to indicate that queuing new requests must
stop. After this flag has been set queue draining starts. However,
during the queue draining phase it is still safe to invoke the
queue's request_fn, so QUEUE_FLAG_DYING is a better name for this
flag.
This patch has been generated by running the following command
over the kernel source tree:
git grep -lEw 'blk_queue_dead|QUEUE_FLAG_DEAD' |
xargs sed -i.tmp -e 's/blk_queue_dead/blk_queue_dying/g' \
-e 's/QUEUE_FLAG_DEAD/QUEUE_FLAG_DYING/g'; \
sed -i.tmp -e "s/QUEUE_FLAG_DYING$(printf \\t)*5/QUEUE_FLAG_DYING$(printf \\t)5/g" \
include/linux/blkdev.h; \
sed -i.tmp -e 's/ DEAD/ DYING/g' -e 's/dead queue/a dying queue/' \
-e 's/Dead queue/A dying queue/' block/blk-core.c
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: James Bottomley <JBottomley@Parallels.com>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Chanho Min <chanho.min@lge.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Now that mod_delayed_work() is safe to call from IRQ handlers,
__cancel_delayed_work() followed by queue_delayed_work() can be
replaced with mod_delayed_work().
Most conversions are straight-forward except for the following.
* net/core/link_watch.c: linkwatch_schedule_work() was doing a quite
elaborate dancing around its delayed_work. Collapse it such that
linkwatch_work is queued for immediate execution if LW_URGENT and
existing timer is kept otherwise.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
system_nrt[_freezable]_wq are now spurious. Mark them deprecated and
convert all users to system[_freezable]_wq.
If you're cc'd and wondering what's going on: Now all workqueues are
non-reentrant, so there's no reason to use system_nrt[_freezable]_wq.
Please use system[_freezable]_wq instead.
This patch doesn't make any functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-By: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: David Airlie <airlied@linux.ie>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Block layer very lazy allocation of ioc. It waits until the moment
ioc is absolutely necessary; unfortunately, that time could be inside
queue lock and __get_request() performs unlock - try alloc - retry
dancing.
Just allocate it up-front on entry to block layer. We're not saving
the rain forest by deferring it to the last possible moment and
complicating things unnecessarily.
This patch is to prepare for further updates to request allocation
path.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
tg_stats_alloc_lock nests inside queue lock and should always be held
with irq disabled. throtl_pd_{init|exit}() were using non-irqsafe
spinlock ops which triggered inverse lock ordering via irq warning via
RCU freeing of blkg invoking throtl_pd_exit() w/o disabling IRQ.
Update both functions to use irq safe operations.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
LKML-Reference: <1335339396.16988.80.camel@lappy>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.18 (GNU/Linux)
iQEcBAABAgAGBQJPnb50AAoJEHm+PkMAQRiGAE0H/A4zFZIUGmF3miKPDYmejmrZ
oVDYxVAu6JHjHWhu8E3VsinvyVscowjV8dr15eSaQzmDmRkSHAnUQ+dB7Di7jLC2
MNopxsWjwyZ8zvvr3rFR76kjbWKk/1GYytnf7GPZLbJQzd51om2V/TY/6qkwiDSX
U8Tt7ihSgHAezefqEmWp2X/1pxDCEt+VFyn9vWpkhgdfM1iuzF39MbxSZAgqDQ/9
JJrBHFXhArqJguhENwL7OdDzkYqkdzlGtS0xgeY7qio2CzSXxZXK4svT6FFGA8Za
xlAaIvzslDniv3vR2ZKd6wzUwFHuynX222hNim3QMaYdXm012M+Nn1ufKYGFxI0=
=4d4w
-----END PGP SIGNATURE-----
Merge tag 'v3.4-rc5' into for-3.5/core
The core branch is behind driver commits that we want to build
on for 3.5, hence I'm pulling in a later -rc.
Linux 3.4-rc5
Conflicts:
Documentation/feature-removal-schedule.txt
Signed-off-by: Jens Axboe <axboe@kernel.dk>
There's no reason to keep blkcg_policy_ops separate. Collapse it into
blkcg_policy.
This patch doesn't introduce any functional change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently blkg_policy_data carries policy specific data as char flex
array instead of being embedded in policy specific data. This was
forced by oddities around blkg allocation which are all gone now.
This patch makes blkg_policy_data embedded in policy specific data -
throtl_grp and cfq_group so that it's more conventional and consistent
with how io_cq is handled.
* blkcg_policy->pdata_size is renamed to ->pd_size.
* Functions which used to take void *pdata now takes struct
blkg_policy_data *pd.
* blkg_to_pdata/pdata_to_blkg() updated to blkg_to_pd/pd_to_blkg().
* Dummy struct blkg_policy_data definition added. Dummy
pdata_to_blkg() definition was unused and inconsistent with the
non-dummy version - correct dummy pd_to_blkg() added.
* throtl and cfq updated accordingly.
* As dummy blkg_to_pd/pd_to_blkg() are provided,
blkg_to_cfqg/cfqg_to_blkg() don't need to be ifdef'd. Moved outside
ifdef block.
This patch doesn't introduce any functional change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
During the recent blkcg cleanup, most of blkcg API has changed to such
extent that mass renaming wouldn't cause any noticeable pain. Take
the chance and cleanup the naming.
* Rename blkio_cgroup to blkcg.
* Drop blkio / blkiocg prefixes and consistently use blkcg.
* Rename blkio_group to blkcg_gq, which is consistent with io_cq but
keep the blkg prefix / variable name.
* Rename policy method type and field names to signify they're dealing
with policy data.
* Rename blkio_policy_type to blkcg_policy.
This patch doesn't cause any functional change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkio_group->path[] stores the path of the associated cgroup and is
used only for debug messages. Just format the path from blkg->cgroup
when printing debug messages.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
* All_q_list is unused. Drop all_q_{mutex|list}.
* @for_root of blkg_lookup_create() is always %false when called from
outside blk-cgroup.c proper. Factor out __blkg_lookup_create() so
that it doesn't check whether @q is bypassing and use the
underscored version for the @for_root callsite.
* blkg_destroy_all() is used only from blkcg proper and @destroy_root
is always %true. Make it static and drop @destroy_root.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
All blkcg policies were assumed to be enabled on all request_queues.
Due to various implementation obstacles, during the recent blkcg core
updates, this was temporarily implemented as shooting down all !root
blkgs on elevator switch and policy [de]registration combined with
half-broken in-place root blkg updates. In addition to being buggy
and racy, this meant losing all blkcg configurations across those
events.
Now that blkcg is cleaned up enough, this patch replaces the temporary
implementation with proper per-queue policy activation. Each blkcg
policy should call the new blkcg_[de]activate_policy() to enable and
disable the policy on a specific queue. blkcg_activate_policy()
allocates and installs policy data for the policy for all existing
blkgs. blkcg_deactivate_policy() does the reverse. If a policy is
not enabled for a given queue, blkg printing / config functions skip
the respective blkg for the queue.
blkcg_activate_policy() also takes care of root blkg creation, and
cfq_init_queue() and blk_throtl_init() are updated accordingly.
This replaces blkcg_bypass_{start|end}() and update_root_blkg_pd()
unnecessary. Dropped.
v2: cfq_init_queue() was returning uninitialized @ret on root_group
alloc failure if !CONFIG_CFQ_GROUP_IOSCHED. Fixed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
With per-queue policy activation, root blkg creation will be moved to
blkcg core. Add q->root_blkg in preparation. For blk-throtl, this
replaces throtl_data->root_tg; however, cfq needs to keep
cfqd->root_group for !CONFIG_CFQ_GROUP_IOSCHED.
This is to prepare for per-queue policy activation and doesn't cause
any functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add @pol to blkg_conf_prep() and let it return with queue lock held
(to be released by blkg_conf_finish()). Note that @pol isn't used
yet.
This is to prepare for per-queue policy activation and doesn't cause
any visible difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Remove BLKIO_POLICY_* enums and let blkio_policy_register() allocate
@pol->plid dynamically on registration. The maximum number of blkcg
policies which can be registered at the same time is defined by
BLKCG_MAX_POLS constant added to include/linux/blkdev.h.
Note that blkio_policy_register() now may fail. Policy init functions
updated accordingly and unnecessary ifdefs removed from cfq_init().
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The two functions were taking "enum blkio_policy_id plid". Make them
take "const struct blkio_policy_type *pol" instead.
This is to prepare for per-queue policy activation and doesn't cause
any functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Now that all stat handling code lives in policy implementations,
there's no need to encode policy ID in cft->private.
* Export blkcg_prfill_[rw]stat() from blkcg, remove
blkcg_print_[rw]stat(), and implement cfqg_print_[rw]stat() which
use hard-code BLKIO_POLICY_PROP.
* Use cft->private for offset of the target field directly and drop
BLKCG_STAT_{PRIV|POL|OFF}().
Signed-off-by: Tejun Heo <tj@kernel.org>
Now that all conf and stat fields are moved into policy specific
blkio_policy_data->pdata areas, there's no reason to use
blkio_policy_data itself in prfill functions. Pass around @pd->pdata
instead of @pd.
Signed-off-by: Tejun Heo <tj@kernel.org>
blkio_cgroup_conf->iops and ->bps are owned by blk-throttle and has no
reason to be defined in blkcg core. Drop them and let conf setting
functions directly manipulate throtl_grp->bps[] and ->iops[].
This makes blkio_group_conf empty. Drop it.
Signed-off-by: Tejun Heo <tj@kernel.org>
blkio_group_stats_cpu is used only by blk-throtl and has no reason to
be defined in blkcg core.
* Move blkio_group_stats_cpu to blk-throttle.c and rename it to
tg_stats_cpu.
* blkg_policy_data->stats_cpu is replaced with throtl_grp->stats_cpu.
prfill functions updated accordingly.
* All related macros / functions are renamed so that they have tg_
prefix and the unnecessary @pol arguments are dropped.
* Per-cpu stats allocation code is also moved from blk-cgroup.c to
blk-throttle.c and gets simplified to only deal with
BLKIO_POLICY_THROTL. percpu stat free is performed by the exit
method throtl_exit_blkio_group().
* throtl_reset_group_stats() implemented for
blkio_reset_group_stats_fn method so that tg->stats_cpu can be
reset.
Signed-off-by: Tejun Heo <tj@kernel.org>
blkio_group_stats_cpu is used to count dispatch stats using per-cpu
counters. This is used by both blk-throtl and cfq-iosched but the
sharing is rather silly.
* cfq-iosched doesn't need per-cpu dispatch stats. cfq always updates
those stats while holding queue_lock.
* blk-throtl needs per-cpu dispatch stats but only service_bytes and
serviced. It doesn't make use of sectors.
This patch makes cfq add and use global stats for service_bytes,
serviced and sectors, removes per-cpu sectors counter and moves
per-cpu stat printing code to blk-throttle.c.
Signed-off-by: Tejun Heo <tj@kernel.org>
As with conf/stats file handling code, there's no reason for stat
update code to live in blkcg core with policies calling into update
them. The current organization is both inflexible and complex.
This patch moves stat update code to specific policies. All
blkiocg_update_*_stats() functions which deal with BLKIO_POLICY_PROP
stats are collapsed into their cfq_blkiocg_update_*_stats()
counterparts. blkiocg_update_dispatch_stats() is used by both
policies and duplicated as throtl_update_dispatch_stats() and
cfq_blkiocg_update_dispatch_stats(). This will be cleaned up later.
Signed-off-by: Tejun Heo <tj@kernel.org>
blkcg conf/stat handling is convoluted in that details which belong to
specific policy implementations are all out in blkcg core and then
policies hook into core layer to access and manipulate confs and
stats. This sadly achieves both inflexibility (confs/stats can't be
modified without messing with blkcg core) and complexity (all the
call-ins and call-backs).
The previous patches restructured conf and stat handling code such
that they can be separated out. This patch relocates the file
handling part. All conf/stat file handling code which belongs to
BLKIO_POLICY_PROP is moved to cfq-iosched.c and all
BKLIO_POLICY_THROTL code to blk-throtl.c.
The move is verbatim except for blkio_update_group_{weight|bps|iops}()
callbacks which relays conf changes to policies. The configuration
settings are handled in policies themselves so the relaying isn't
necessary. Conf setting functions are modified to directly call
per-policy update functions and the relaying mechanism is dropped.
Signed-off-by: Tejun Heo <tj@kernel.org>
Make blk-throttle call bio_associate_current() on bios being delayed
such that they get issued to block layer with the original io_context.
This allows stacking blk-throttle and cfq-iosched propio policies.
bios will always be issued with the correct ioc and blkcg whether it
gets delayed by blk-throttle or not.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Implement bio_blkio_cgroup() which returns the blkcg associated with
the bio if exists or %current's blkcg, and use it in blk-throttle and
cfq-iosched propio. This makes both cgroup policies honor task
association for the bio instead of always assuming %current.
As nobody is using bio_set_task() yet, this doesn't introduce any
behavior change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Now that blkg additions / removals are always done under both q and
blkcg locks, the only places RCU locking is necessary are
blkg_lookup[_create]() for lookup w/o blkcg lock. This patch drops
unncessary RCU locking replacing it with plain blkcg locking as
necessary.
* blkiocg_pre_destroy() already perform proper locking and don't need
RCU. Dropped.
* blkio_read_blkg_stats() now uses blkcg->lock instead of RCU read
lock. This isn't a hot path.
* Now unnecessary synchronize_rcu() from queue exit paths removed.
This makes q->nr_blkgs unnecessary. Dropped.
* RCU annotation on blkg->q removed.
-v2: Vivek pointed out that blkg_lookup_create() still needs to be
called under rcu_read_lock(). Updated.
-v3: After the update, stats_lock locking in blkio_read_blkg_stats()
shouldn't be using _irq variant as it otherwise ends up enabling
irq while blkcg->lock is locked. Fixed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently, blkg is per cgroup-queue-policy combination. This is
unnatural and leads to various convolutions in partially used
duplicate fields in blkg, config / stat access, and general management
of blkgs.
This patch make blkg's per cgroup-queue and let them serve all
policies. blkgs are now created and destroyed by blkcg core proper.
This will allow further consolidation of common management logic into
blkcg core and API with better defined semantics and layering.
As a transitional step to untangle blkg management, elvswitch and
policy [de]registration, all blkgs except the root blkg are being shot
down during elvswitch and bypass. This patch adds blkg_root_update()
to update root blkg in place on policy change. This is hacky and racy
but should be good enough as interim step until we get locking
simplified and switch over to proper in-place update for all blkgs.
-v2: Root blkgs need to be updated on elvswitch too and blkg_alloc()
comment wasn't updated according to the function change. Fixed.
Both pointed out by Vivek.
-v3: v2 updated blkg_destroy_all() to invoke update_root_blkg_pd() for
all policies. This freed root pd during elvswitch before the
last queue finished exiting and led to oops. Directly invoke
update_root_blkg_pd() only on BLKIO_POLICY_PROP from
cfq_exit_queue(). This also is closer to what will be done with
proper in-place blkg update. Reported by Vivek.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
With the previous patch to move blkg list heads and counters to
request_queue and blkg, logic to manage them in both policies are
almost identical and can be moved to blkcg core.
This patch moves blkg link logic into blkg_lookup_create(), implements
common blkg unlink code in blkg_destroy(), and updates
blkg_destory_all() so that it's policy specific and can skip root
group. The updated blkg_destroy_all() is now used to both clear queue
for bypassing and elv switching, and release all blkgs on q exit.
This patch introduces a race window where policy [de]registration may
race against queue blkg clearing. This can only be a problem on cfq
unload and shouldn't be a real problem in practice (and we have many
other places where this race already exists). Future patches will
remove these unlikely races.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently, specific policy implementations are responsible for
maintaining list and number of blkgs. This duplicates code
unnecessarily, and hinders factoring common code and providing blkcg
API with better defined semantics.
After this patch, request_queue hosts list heads and counters and blkg
has list nodes for both policies. This patch only relocates the
necessary fields and the next patch will actually move management code
into blkcg core.
Note that request_queue->blkg_list[] and ->nr_blkgs[] are hardcoded to
have 2 elements. This is to avoid include dependency and will be
removed by the next patch.
This patch doesn't introduce any behavior change.
-v2: Now unnecessary conditional on CONFIG_BLK_CGROUP_MODULE removed
as pointed out by Vivek.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkg is scheduled to be unified for all policies and thus there won't
be one-to-one mapping from blkg to policy. Update stat related
functions to take explicit @pol or @plid arguments and not use
blkg->plid.
This is painful for now but most of specific stat interface functions
will be replaced with a handful of generic helpers.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently, blkcg policy implementations manage blkg refcnt duplicating
mostly identical code in both policies. This patch moves refcnt to
blkg and let blkcg core handle refcnt and freeing of blkgs.
* cfq blkgs now also get freed via RCU.
* cfq blkgs lose RB_EMPTY_ROOT() sanity check on blkg free. If
necessary, we can add blkio_exit_group_fn() to resurrect this.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently, blkg's are embedded in private data blkcg policy private
data structure and thus allocated and freed by policies. This leads
to duplicate codes in policies, hinders implementing common part in
blkcg core with strong semantics, and forces duplicate blkg's for the
same cgroup-q association.
This patch introduces struct blkg_policy_data which is a separate data
structure chained from blkg. Policies specifies the amount of private
data it needs in its blkio_policy_type->pdata_size and blkcg core
takes care of allocating them along with blkg which can be accessed
using blkg_to_pdata(). blkg can be determined from pdata using
pdata_to_blkg(). blkio_alloc_group_fn() method is accordingly updated
to blkio_init_group_fn().
For consistency, tg_of_blkg() and cfqg_of_blkg() are replaced with
blkg_to_tg() and blkg_to_cfqg() respectively, and functions to map in
the reverse direction are added.
Except that policy specific data now lives in a separate data
structure from blkg, this patch doesn't introduce any functional
difference.
This will be used to unify blkg's for different policies.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently block core calls directly into blk-throttle for init, drain
and exit. This patch adds blkcg_{init|drain|exit}_queue() which wraps
the blk-throttle functions. This is to give more control and
visiblity to blkcg core layer for proper layering. Further patches
will add logic common to blkcg policies to the functions.
While at it, collapse blk_throtl_release() into blk_throtl_exit().
There's no reason to keep them separate.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently, blkg points to the associated blkcg via its css_id. This
unnecessarily complicates dereferencing blkcg. Let blkg hold a
reference to the associated blkcg and point directly to it and disable
css_id on blkio_subsys.
This change requires splitting blkiocg_destroy() into
blkiocg_pre_destroy() and blkiocg_destroy() so that all blkg's can be
destroyed and all the blkcg references held by them dropped during
cgroup removal.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkg->dev is dev_t recording the device number of the block device for
the associated request_queue. It is used to identify the associated
block device when printing out configuration or stats.
This is redundant to begin with. A blkg is an association between a
cgroup and a request_queue and it of course is possible to reach
request_queue from blkg and synchronization conventions are in place
for safe q dereferencing, so this shouldn't be necessary from the
beginning. Furthermore, it's initialized by sscanf()ing the device
name of backing_dev_info. The mind boggles.
Anyways, if blkg is visible under rcu lock, we *know* that the
associated request_queue hasn't gone away yet and its bdi is
registered and alive - blkg can't be created for request_queue which
hasn't been fully initialized and it can't go away before blkg is
removed.
Let stat and conf read functions get device name from
blkg->q->backing_dev_info.dev and pass it down to printing functions
and remove blkg->dev.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkcg is very peculiar in that it allows setting and remembering
configurations for non-existent devices by maintaining separate data
structures for configuration.
This behavior is completely out of the usual norms and outright
confusing; furthermore, it uses dev_t number to match the
configuration to devices, which is unpredictable to begin with and
becomes completely unuseable if EXT_DEVT is fully used.
It is wholely unnecessary - we already have fully functional userland
mechanism to program devices being hotplugged which has full access to
device identification, connection topology and filesystem information.
Add a new struct blkio_group_conf which contains all blkcg
configurations to blkio_group and let blkio_group, which can be
created iff the associated device exists and is removed when the
associated device goes away, carry all configurations.
Note that, after this patch, all newly created blkg's will always have
the default configuration (unlimited for throttling and blkcg's weight
for propio).
This patch makes blkio_policy_node meaningless but doesn't remove it.
The next patch will.
-v2: Updated to retry after short sleep if blkg lookup/creation failed
due to the queue being temporarily bypassed as indicated by
-EBUSY return. Pointed out by Vivek.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently both blk-throttle and cfq-iosched implement their own
blkio_group creation code in throtl_get_tg() and cfq_get_cfqg(). This
patch factors out the common code into blkg_lookup_create(), which
returns ERR_PTR value so that transitional failures due to queue
bypass can be distinguished from other failures.
* New plkio_policy_ops methods blkio_alloc_group_fn() and
blkio_link_group_fn added. Both are transitional and will be
removed once the blkg management code is fully moved into
blk-cgroup.c.
* blkio_alloc_group_fn() allocates policy-specific blkg which is
usually a larger data structure with blkg as the first entry and
intiailizes it. Note that initialization of blkg proper, including
percpu stats, is responsibility of blk-cgroup proper.
Note that default config (weight, bps...) initialization is done
from this method; otherwise, we end up violating locking order
between blkcg and q locks via blkcg_get_CONF() functions.
* blkio_link_group_fn() is called under queue_lock and responsible for
linking the blkg to the queue. blkcg side is handled by blk-cgroup
proper.
* The common blkg creation function is named blkg_lookup_create() and
blkiocg_lookup_group() is renamed to blkg_lookup() for consistency.
Also, throtl / cfq related functions are similarly [re]named for
consistency.
This simplifies blkcg policy implementations and enables further
cleanup.
-v2: Vivek noticed that blkg_lookup_create() incorrectly tested
blk_queue_dead() instead of blk_queue_bypass() leading a user of
the function ending up creating a new blkg on bypassing queue.
This is a bug introduced while relocating bypass patches before
this one. Fixed.
-v3: ERR_PTR patch folded into this one. @for_root added to
blkg_lookup_create() to allow creating root group on a bypassed
queue during elevator switch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
For root blkg, blk_throtl_init() was using throtl_alloc_tg()
explicitly and cfq_init_queue() was manually initializing embedded
cfqd->root_group, adding unnecessarily different code paths to blkg
handling.
Make both use the usual blkio_group get functions - throtl_get_tg()
and cfq_get_cfqg() - for the root blkio_group too. Note that
blk_throtl_init() callsite is pushed downwards in
blk_alloc_queue_node() so that @q is sufficiently initialized for
throtl_get_tg().
This simplifies root blkg handling noticeably for cfq and will allow
further modularization of blkcg API.
-v2: Vivek pointed out that using cfq_get_cfqg() won't work if
CONFIG_CFQ_GROUP_IOSCHED is disabled. Fix it by factoring out
initialization of base part of cfqg into cfq_init_cfqg_base() and
alloc/init/free explicitly if !CONFIG_CFQ_GROUP_IOSCHED.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkgio_group is association between a block cgroup and a queue for a
given policy. Using opaque void * for association makes things
confusing and hinders factoring of common code. Use request_queue *
and, if necessary, policy id instead.
This will help block cgroup API cleanup.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
In both blkg get functions - throtl_get_tg() and cfq_get_cfqg(),
instead of obtaining blkcg of %current explicitly, let the caller
specify the blkcg to use as parameter and make both functions hold on
to the blkcg.
This is part of block cgroup interface cleanup and will help making
blkcg API more modular.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
rcu_read_lock() in throtl_get_tb() and cfq_get_cfqg() holds onto
@blkcg while looking up blkg. For API cleanup, the next patch will
make the caller responsible for determining @blkcg to look blkg from
and let them specify it as a parameter. Move rcu read locking out to
the callers to prepare for the change.
-v2: Originally this patch was described as a fix for RCU read locking
bug around @blkg, which Vivek pointed out to be incorrect. It
was from misunderstanding the role of rcu locking as protecting
@blkg not @blkcg. Patch description updated.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Elevator switch may involve changes to blkcg policies. Implement
shoot down of blkio_groups.
Combined with the previous bypass updates, the end goal is updating
blkcg core such that it can ensure that blkcg's being affected become
quiescent and don't have any per-blkg data hanging around before
commencing any policy updates. Until queues are made aware of the
policies that applies to them, as an interim step, all per-policy blkg
data will be shot down.
* blk-throtl doesn't need this change as it can't be disabled for a
live queue; however, update it anyway as the scheduled blkg
unification requires this behavior change. This means that
blk-throtl configuration will be unnecessarily lost over elevator
switch. This oddity will be removed after blkcg learns to associate
individual policies with request_queues.
* blk-throtl dosen't shoot down root_tg. This is to ease transition.
Unified blkg will always have persistent root group and not shooting
down root_tg for now eases transition to that point by avoiding
having to update td->root_tg and is safe as blk-throtl can never be
disabled
-v2: Vivek pointed out that group list is not guaranteed to be empty
on return from clear function if it raced cgroup removal and
lost. Fix it by waiting a bit and retrying. This kludge will
soon be removed once locking is updated such that blkg is never
in limbo state between blkcg and request_queue locks.
blk-throtl no longer shoots down root_tg to avoid breaking
td->root_tg.
Also, Nest queue_lock inside blkio_list_lock not the other way
around to avoid introduce possible deadlock via blkcg lock.
-v3: blkcg_clear_queue() repositioned and renamed to
blkg_destroy_all() to increase consistency with later changes.
cfq_clear_queue() updated to check q->elevator before
dereferencing it to avoid NULL dereference on not fully
initialized queues (used by later change).
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Extend queue bypassing such that dying queue is always bypassing and
blk-throttle is drained on bypass. With blkcg policies updated to
test blk_queue_bypass() instead of blk_queue_dead(), this ensures that
no bio or request is held by or going through blkcg policies on a
bypassing queue.
This will be used to implement blkg cleanup on elevator switches and
policy changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
There are a number of QUEUE_FLAG_DEAD tests. Add blk_queue_dead()
macro and use it.
This patch doesn't introduce any functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
request_queue is refcounted but actually depdends on lifetime
management from the queue owner - on blk_cleanup_queue(), block layer
expects that there's no request passing through request_queue and no
new one will.
This is fundamentally broken. The queue owner (e.g. SCSI layer)
doesn't have a way to know whether there are other active users before
calling blk_cleanup_queue() and other users (e.g. bsg) don't have any
guarantee that the queue is and would stay valid while it's holding a
reference.
With delay added in blk_queue_bio() before queue_lock is grabbed, the
following oops can be easily triggered when a device is removed with
in-flight IOs.
sd 0:0:1:0: [sdb] Stopping disk
ata1.01: disabled
general protection fault: 0000 [#1] PREEMPT SMP
CPU 2
Modules linked in:
Pid: 648, comm: test_rawio Not tainted 3.1.0-rc3-work+ #56 Bochs Bochs
RIP: 0010:[<ffffffff8137d651>] [<ffffffff8137d651>] elv_rqhash_find+0x61/0x100
...
Process test_rawio (pid: 648, threadinfo ffff880019efa000, task ffff880019ef8a80)
...
Call Trace:
[<ffffffff8137d774>] elv_merge+0x84/0xe0
[<ffffffff81385b54>] blk_queue_bio+0xf4/0x400
[<ffffffff813838ea>] generic_make_request+0xca/0x100
[<ffffffff81383994>] submit_bio+0x74/0x100
[<ffffffff811c53ec>] dio_bio_submit+0xbc/0xc0
[<ffffffff811c610e>] __blockdev_direct_IO+0x92e/0xb40
[<ffffffff811c39f7>] blkdev_direct_IO+0x57/0x60
[<ffffffff8113b1c5>] generic_file_aio_read+0x6d5/0x760
[<ffffffff8118c1ca>] do_sync_read+0xda/0x120
[<ffffffff8118ce55>] vfs_read+0xc5/0x180
[<ffffffff8118cfaa>] sys_pread64+0x9a/0xb0
[<ffffffff81afaf6b>] system_call_fastpath+0x16/0x1b
This happens because blk_queue_cleanup() destroys the queue and
elevator whether IOs are in progress or not and DEAD tests are
sprinkled in the request processing path without proper
synchronization.
Similar problem exists for blk-throtl. On queue cleanup, blk-throtl
is shutdown whether it has requests in it or not. Depending on
timing, it either oopses or throttled bios are lost putting tasks
which are waiting for bio completion into eternal D state.
The way it should work is having the usual clear distinction between
shutdown and release. Shutdown drains all currently pending requests,
marks the queue dead, and performs partial teardown of the now
unnecessary part of the queue. Even after shutdown is complete,
reference holders are still allowed to issue requests to the queue
although they will be immmediately failed. The rest of teardown
happens on release.
This patch makes the following changes to make blk_queue_cleanup()
behave as proper shutdown.
* QUEUE_FLAG_DEAD is now set while holding both q->exit_mutex and
queue_lock.
* Unsynchronized DEAD check in generic_make_request_checks() removed.
This couldn't make any meaningful difference as the queue could die
after the check.
* blk_drain_queue() updated such that it can drain all requests and is
now called during cleanup.
* blk_throtl updated such that it checks DEAD on grabbing queue_lock,
drains all throttled bios during cleanup and free td when queue is
released.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_throtl_bio() and throtl_get_tg() have rather unusual interface.
* throtl_get_tg() returns pointer to a valid tg or ERR_PTR(-ENODEV),
and drops queue_lock in the latter case. Different locking context
depending on return value is error-prone and DEAD state is scheduled
to be protected by queue_lock anyway. Move DEAD check inside
queue_lock and return valid tg or NULL.
* blk_throtl_bio() indicates return status both with its return value
and in/out param **@bio. The former is used to indicate whether
queue is found to be dead during throtl processing. The latter
whether the bio is throttled.
There's no point in returning DEAD check result from
blk_throtl_bio(). The queue can die after blk_throtl_bio() is
finished but before make_request_fn() grabs queue lock.
Make it take *@bio instead and return boolean result indicating
whether the request is throttled or not.
This patch doesn't cause any visible functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_get/put_queue() in scsi_cmd_ioctl() and throtl_get_tg() are
completely bogus. The caller must have a reference to the queue on
entry and taking an extra reference doesn't change anything.
For scsi_cmd_ioctl(), the only effect is that it ends up checking
QUEUE_FLAG_DEAD on entry; however, this is bogus as queue can die
right after blk_get_queue(). Dead queue should be and is handled in
request issue path (it's somewhat broken now but that's a separate
problem and doesn't affect this one much).
throtl_get_tg() incorrectly assumes that q is rcu freed. Also, it
doesn't check return value of blk_get_queue(). If the queue is
already dead, it ends up doing an extra put.
Drop them.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_throtl interface is block internal and there's no reason to have
them in linux/blkdev.h. Move them to block/blk.h.
This patch doesn't introduce any functional change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
read request is always sync. Using rw_is_sync() to determine
if a bio is sync.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
The total of two unsigned values should also be unsigned.
Update throtl_log output to unsigned.
Update total_nr_queued test to non-zero to be the
same as the other total_nr_queued tests.
Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Use the compiler to verify format strings and arguments.
Fix fallout.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Currently we take a queue lock on each bio to check if there are any
throttling rules associated with the group and also update the stats.
Now access the group under rcu and update the stats without taking
the queue lock. Queue lock is taken only if there are throttling rules
associated with the group.
So the common case of root group when there are no rules, save
unnecessary pounding of request queue lock.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Currently we take blkg_stat lock for even updating the stats. So even if
a group has no throttling rules (common case for root group), we end
up taking blkg_lock, for updating the stats.
Make dispatch stats per cpu so that these can be updated without taking
blkg lock.
If cpu goes offline, these stats simply disappear. No protection has
been provided for that yet. Do we really need anything for that?
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Soon we will allow accessing a throtl_grp under rcu_read_lock(). Hence
start freeing up throtl_grp after one rcu grace period.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Use same helper function for root group as we use with dynamically
allocated groups to add it to various lists.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
A helper function for the code which is used at 2-3 places. Makes reading
code little easier.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Currently, we allocate root throtl_grp statically. But as we will be
introducing per cpu stat pointers and that will be allocated
dynamically even for root group, we might as well make whole root
throtl_grp allocation dynamic and treat it in same manner as other
groups.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Currently, all the cfq_group or throtl_group allocations happen while
we are holding ->queue_lock and sleeping is not allowed.
Soon, we will move to per cpu stats and also need to allocate the
per group stats. As one can not call alloc_percpu() from atomic
context as it can sleep, we need to drop ->queue_lock, allocate the
group, retake the lock and continue processing.
In throttling code, I check the queue DEAD flag again to make sure
that driver did not call blk_cleanup_queue() in the mean time.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
