The block device is backed by the transport so we must ensure that the
transport driver will not be removed until all references are released.
Otherwise, we might end up referencing freed memory.
Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Nitzan Carmi <nitzanc@mellanox.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
When the io queues setup or tagset allocation failed, ctrl.tagset is
NULL. But the scan work will still be queued and executed, then panic
comes up due to NULL pointer reference of ctrl.tagset.
To fix this, add a new ctrl state NVME_CTRL_ADMIN_ONLY to inidcate only
admin queue is live. When non io queues or tagset allocation failed, ctrl
enters into this state, scan work will not be started. But async event
work and nvme dev ioctl will be still available. This will be helpful to
do further investigation and recovery.
Suggested-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
When an NVMe controller reports RTD3 Entry Latency larger than the value
of shutdown_timeout module parameter, we update the shutdown_timeout
accordingly to honor RTD3 Entry Latency. Use an informational debug level
instead of a warning level for it.
Signed-off-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Make it symmetric to nvmet_alloc_ctrl().
Signed-off-by: Israel Rukshin <israelr@mellanox.com>
Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Remove the allocated id on error.
Signed-off-by: Israel Rukshin <israelr@mellanox.com>
Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
The local variable __size__ will be set a bit later in a for-loop.
Remove the explicit initialization at the beginning of this function.
Signed-off-by: Minwoo Im <minwoo.im.dev@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
NVMe transport driver module unload may (and usually does) trigger
iteration over the active controllers and delete them all (sometimes
under a mutex). However, a controller can be created concurrently with
module unload which can lead to leakage of resources (most important char
device node leakage) in case the controller creation occured after the
unload delete and drain sequence. To protect against this, we take a
module reference to guarantee that the nvme transport driver is not
unloaded while creating a controller.
Signed-off-by: Roy Shterman <roys@lightbitslabs.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
The current fc transport add_port routine validates that there is a
matching port to the target port config. It then takes a reference
on the targetport. The del_port removes the reference.
Unfortunately, if the LLDD undergoes a hw reset or driver unload and
wants to unreg the targetport, due to the reference, the targetport
effectively can't be removed. It requires the admin to remove the
port from the nvmet config first, which calls the del_port.
Note: it appears nvmetcli clear skips over the del_port call (I'm
not attempting to change that).
There's no real reason to take the reference. With FC, there is nothing
to enable or disable as the presence of the FC targetport implicitly
means its enabled, and removal of the targtport means its disabled.
Change add_port to simply validate and change remove_port to a noop.
No references are taken on the targetport.
Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
The split between what the host accesses on its flows vs what the
target side accesses was flawed. Abort handling didn't properly
clear initiator vs target structure cross-reference and locks
weren't used for synchronization. Thus, there were issues of
freeing structures too soon and access after free.
A couple of these existed pre the IN_ISR mods, but when the
target upcalls were converted to work items, thus adding delays
between the 2 sides of accesses, the problems became pronounced.
Resolve by:
- tracking io state mainly in the tgt-side io structure.
- make the tgt-side io structure released by reference not by
code flow.
- when changing initiator structures, use locks for
synchronization
- aborts are clearly tracked for which side saw the abort, and
after seeing the abort, cross-references are cleared under lock.
Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
The existing fcloop driver expects the target side upcalls to
the transport to context switch, thus the calls into the nvmet layer
are not done in the calling context of the host/initiator down calls.
The xxx_IN_ISR feature flags are used to select this logic.
The xxx_IN_ISR feature flags should go away in the nvmet_fc transport
as no other lldd utilizes them. Both Broadcom and Cavium lldds have their
own non-ISR deferred handlers thus the nvmet calls can be made directly.
This patch converts the paths that make the target upcalls (command
receive, abort receive) such that they schedule a work item rather
than expecting the transport to schedule the work item.
The patch also cleans up the following:
- The completion path from target to host scheduled a host work
element called "work". Rename it "tio_done_work" for code clarity.
- The abort io path called a iniwork item to call the host side
io done. This is no longer needed as the abort routine can make
the same call.
Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
The current fcloop driver gets its lport structure from the private
area co-allocated with the fc_localport. All is fine except the
teardown path, which wants to wait on the completion, which is marked
complete by the delete_localport callback performed after
unregister_localport. The issue is, the nvme_fc transport frees the
localport structure immediately after delete_localport is called,
meaning the original routine is trying to wait on a complete that
was just freed.
Change such that a lport struct is allocated coincident with the
addition and registration of a localport. The private area of the
localport now contains just a backpointer to the real lport struct.
Now, the completion can be waited for, and after completing, the
new structure can be kfree'd.
Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
A test case revealed a race condition of an i/o completing on a thread
parallel to the delete_association generating the aborts for the
outstanding ios on the controller. The i/o completion was freeing the
target fcloop context, thus the abort task referenced the just-freed
memory.
Correct by clearing the target/initiator cross pointers in the io
completion and abort tasks before calling the callbacks. On aborts
that detect already finished io's, ensure the complete context is
called.
Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
It is a bit chatty to report on each queue, log it only for debug
purposes.
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
It is a bit chatty to report on every deleted queue, so keep it for debug
purposes only.
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
We already do that when we are notified in device removal
which is triggered when unregistering as an ib client.
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
In both elevator_switch_mq() and blk_mq_update_nr_hw_queues(), sched tags
can be allocated, and q->nr_hw_queue is used, and race is inevitable, for
example: blk_mq_init_sched() may trigger use-after-free on hctx, which is
freed in blk_mq_realloc_hw_ctxs() when nr_hw_queues is decreased.
This patch fixes the race be holding q->sysfs_lock.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Dispatch may still be in-progress after queue is frozen, so we have to
quiesce queue before switching IO scheduler and updating nr_requests.
Also when switching io schedulers, blk_mq_run_hw_queue() may still be
called somewhere(such as from nvme_reset_work()), and io scheduler's
per-hctx data may not be setup yet, so cause oops even inside
blk_mq_hctx_has_pending(), such as it can be run just between:
ret = e->ops.mq.init_sched(q, e);
AND
ret = e->ops.mq.init_hctx(hctx, i)
inside blk_mq_init_sched().
This reverts commit 7a148c2fcff8330(block: don't call blk_mq_quiesce_queue()
after queue is frozen) basically, and makes sure blk_mq_hctx_has_pending
won't be called if queue is quiesced.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Fixes: 7a148c2fcff83309(block: don't call blk_mq_quiesce_queue() after queue is frozen)
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Don't pass in the hardware queue to __dd_dispatch_request(), since it
leads the reader to believe that we are returning a request for that
specific hardware queue. That's not how mq-deadline works, the state
for determining which request to serve next is shared across all
hardware queues for a device.
Reviewed-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Use the sgl_alloc_order() and sgl_free() functions instead of open
coding these functions.
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Acked-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Use the sgl_alloc() and sgl_free() functions instead of open coding
these functions.
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Use the sgl_alloc() and sgl_free() functions instead of open coding
these functions.
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: James Smart <james.smart@broadcom.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Use the sgl_alloc() and sgl_free() functions instead of open coding
these functions.
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Many kernel drivers contain code that allocates and frees both a
scatterlist and the pages that populate that scatterlist.
Introduce functions in lib/scatterlist.c that perform these tasks
instead of duplicating this functionality in multiple drivers.
Only include these functions in the build if CONFIG_SGL_ALLOC=y
to avoid that the kernel size increases if this functionality is
not used.
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The @head can be wb->b_dirty_time, so update the comment.
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Wang Long <wanglong19@meituan.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
When CONFIG_KASAN is set, all the local variables in this function are
allocated on the stack together, leading to a warning about possible
kernel stack overflow:
drivers/block/DAC960.c: In function 'DAC960_gam_ioctl':
drivers/block/DAC960.c:7061:1: error: the frame size of 2240 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]
By splitting up the function into smaller chunks, we can avoid that and
make the code slightly more readable at the same time. The coding style
in this file is completely nonstandard, and I chose to not touch that
at all, leaving the unconventional intendation unchanged to make it
easier to review the diff.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
In this case, 'sectors' can't be zero at all, so remove the check
and let the bio be split.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
When merging one bvec into segment, if the bvec is too big
to merge, current policy is to move the whole bvec into another
new segment.
This patchset changes the policy into trying to maximize size of
front segments, that means in above situation, part of bvec
is merged into current segment, and the remainder is put
into next segment.
This patch prepares for support multipage bvec because
it can be quite common to see this case and we should try
to make front segments in full size.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
It is enough to check and compute bio->bi_seg_front_size just
after the 1st segment is found, but current code checks that
for each bvec, which is inefficient.
This patch follows the way in __blk_recalc_rq_segments()
for computing bio->bi_seg_front_size, and it is more efficient
and code becomes more readable too.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The bio is always freed after running crypt_free_buffer_pages(), so it
isn't necessary to clear bv->bv_page.
Cc: Mike Snitzer <snitzer@redhat.com>
Cc:dm-devel@redhat.com
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Commit 17347cec15f919901c90(Btrfs: change how we iterate bios in endio)
mentioned that for dio the submitted bio may be fast cloned, we
can't access the bvec table directly for a cloned bio, so use
bio_get_first_bvec() to retrieve the 1st bvec.
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: David Sterba <dsterba@suse.com>
Cc: linux-btrfs@vger.kernel.org
Cc: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Acked: David Sterba <dsterba@suse.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
BTRFS uses bio->bi_vcnt to figure out page numbers, this approach is no
longer valid once we start enabling multipage bvecs.
correct once we start to enable multipage bvec.
Use bio_nr_pages() to do that instead.
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: David Sterba <dsterba@suse.com>
Cc: linux-btrfs@vger.kernel.org
Acked-by: David Sterba <dsterba@suse.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
bcache is the only user of bio_alloc_pages(), so move this function into
bcache, and avoid it being misused in the future.
Also rename it to bch_bio_allo_pages() since it is bcache only.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
All direct access to bvec table are safe even after multipage bvec is
supported.
Cc: linux-bcache@vger.kernel.org
Acked-by: Coly Li <colyli@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
For BIO based DM, some targets aren't ready for dealing with bigger
incoming bio than 1Mbyte, such as crypt target.
Cc: Mike Snitzer <snitzer@redhat.com>
Cc:dm-devel@redhat.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Firstly this patch introduces BVEC_ITER_ALL_INIT for iterating one bio
from start to end.
As we need to support multipage bvecs, don't access bio->bi_io_vec
in copy_to_high_bio_irq(), and just use the standard iterator for that.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We will support multipage bvecs in the future, so change to iterator way
for getting bv_page of bvec from original bio.
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This patch converts 3 users to bio_last_bvec_all(), so that we can go
ahead and convert to multipage bvec.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This patch converts to bio_first_bvec_all() & bio_first_page_all() for
retrieving the 1st bvec/page, and prepares for supporting multipage bvec.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The following helpers are introduced for converting current users of
direct access to bvec table, and prepares for supporting multipage bvec:
bio_pages_all()
bio_first_bvec_all()
bio_first_page_all()
bio_last_bvec_all()
All are named as bio_*_all() to following bio_for_each_segment_all(),
they can only be used on bio of !bio_flagged(bio, BIO_CLONED), that means
the whole bvec table is covered.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Commit a33801e8b4 ("block, bfq: move debug blkio stats behind
CONFIG_DEBUG_BLK_CGROUP") introduced two batches of confusing ifdefs:
one reported in [1], plus a similar one in another function. This
commit removes both batches, in the way suggested in [1].
[1] https://www.spinics.net/lists/linux-block/msg20043.html
Fixes: a33801e8b4 ("block, bfq: move debug blkio stats behind CONFIG_DEBUG_BLK_CGROUP")
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Tested-by: Luca Miccio <lucmiccio@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
BFQ privileges the I/O of soft real-time applications, such as video
players, to guarantee to these application a high bandwidth and a low
latency. In this respect, it is not easy to correctly detect when an
application is soft real-time. A particularly nasty false positive is
that of an I/O-bound application that occasionally happens to meet all
requirements to be deemed as soft real-time. After being detected as
soft real-time, such an application monopolizes the device. Fortunately,
BFQ will realize soon that the application is actually not soft
real-time and suspend every privilege. Yet, the application may happen
again to be wrongly detected as soft real-time, and so on.
As highlighted by our tests, this problem causes BFQ to occasionally
fail to guarantee a high responsiveness, in the presence of heavy
background I/O workloads. The reason is that the background workload
happens to be detected as soft real-time, more or less frequently,
during the execution of the interactive task under test. To give an
idea, because of this problem, Libreoffice Writer occasionally takes 8
seconds, instead of 3, to start up, if there are sequential reads and
writes in the background, on a Kingston SSDNow V300.
This commit addresses this issue by leveraging the following facts.
The reason why some applications are detected as soft real-time despite
all BFQ checks to avoid false positives, is simply that, during high
CPU or storage-device load, I/O-bound applications may happen to do
I/O slowly enough to meet all soft real-time requirements, and pass
all BFQ extra checks. Yet, this happens only for limited time periods:
slow-speed time intervals are usually interspersed between other time
intervals during which these applications do I/O at a very high speed.
To exploit these facts, this commit introduces a little change, in the
detection of soft real-time behavior, to systematically consider also
the recent past: the higher the speed was in the recent past, the
later next I/O should arrive for the application to be considered as
soft real-time. At the beginning of a slow-speed interval, the minimum
arrival time allowed for the next I/O usually happens to still be so
high, to fall *after* the end of the slow-speed period itself. As a
consequence, the application does not risk to be deemed as soft
real-time during the slow-speed interval. Then, during the next
high-speed interval, the application cannot, evidently, be deemed as
soft real-time (exactly because of its speed), and so on.
This extra filtering proved to be rather effective: in the above test,
the frequency of false positives became so low that the start-up time
was 3 seconds in all iterations (apart from occasional outliers,
caused by page-cache-management issues, which are out of the scope of
this commit, and cannot be solved by an I/O scheduler).
Tested-by: Lee Tibbert <lee.tibbert@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Angelo Ruocco <angeloruocco90@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
When two or more processes do I/O in a way that the their requests are
sequential in respect to one another, BFQ merges the bfq_queues associated
with the processes. This way the overall I/O pattern becomes sequential,
and thus there is a boost in througput.
These cooperating processes usually start or restart to do I/O shortly
after each other. So, in order to avoid merging non-cooperating processes,
BFQ ensures that none of these queues has been in weight raising for too
long.
In this respect, from commit "block, bfq-sq, bfq-mq: let a queue be merged
only shortly after being created", BFQ checks whether any queue (and not
only weight-raised ones) is doing I/O continuously from too long to be
merged.
This new additional check makes the first one useless: a queue doing
I/O from long enough, if being weight-raised, is also a queue in
weight raising for too long to be merged. Accordingly, this commit
removes the first check.
Signed-off-by: Angelo Ruocco <angeloruocco90@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
In BFQ and CFQ, two processes are said to be cooperating if they do
I/O in such a way that the union of their I/O requests yields a
sequential I/O pattern. To get such a sequential I/O pattern out of
the non-sequential pattern of each cooperating process, BFQ and CFQ
merge the queues associated with these processes. In more detail,
cooperating processes, and thus their associated queues, usually
start, or restart, to do I/O shortly after each other. This is the
case, e.g., for the I/O threads of KVM/QEMU and of the dump
utility. Basing on this assumption, this commit allows a bfq_queue to
be merged only during a short time interval (100ms) after it starts,
or re-starts, to do I/O. This filtering provides two important
benefits.
First, it greatly reduces the probability that two non-cooperating
processes have their queues merged by mistake, if they just happen to
do I/O close to each other for a short time interval. These spurious
merges cause loss of service guarantees. A low-weight bfq_queue may
unjustly get more than its expected share of the throughput: if such a
low-weight queue is merged with a high-weight queue, then the I/O for
the low-weight queue is served as if the queue had a high weight. This
may damage other high-weight queues unexpectedly. For instance,
because of this issue, lxterminal occasionally took 7.5 seconds to
start, instead of 6.5 seconds, when some sequential readers and
writers did I/O in the background on a FUJITSU MHX2300BT HDD. The
reason is that the bfq_queues associated with some of the readers or
the writers were merged with the high-weight queues of some processes
that had to do some urgent but little I/O. The readers then exploited
the inherited high weight for all or most of their I/O, during the
start-up of terminal. The filtering introduced by this commit
eliminated any outlier caused by spurious queue merges in our start-up
time tests.
This filtering also provides a little boost of the throughput
sustainable by BFQ: 3-4%, depending on the CPU. The reason is that,
once a bfq_queue cannot be merged any longer, this commit makes BFQ
stop updating the data needed to handle merging for the queue.
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Angelo Ruocco <angeloruocco90@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
A just-created bfq_queue will certainly be deemed as interactive on
the arrival of its first I/O request, if the low_latency flag is
set. Yet, if the queue is merged with another queue on the arrival of
its first I/O request, it will not have the chance to be flagged as
interactive. Nevertheless, if the queue is then split soon enough, it
has to be flagged as interactive after the split.
To handle this early-merge scenario correctly, BFQ saves the state of
the queue, on the merge, as if the latter had already been deemed
interactive. So, if the queue is split soon, it will get
weight-raised, because the previous state of the queue is resumed on
the split.
Unfortunately, in the act of saving the state of the newly-created
queue, BFQ doesn't check whether the low_latency flag is set, and this
causes early-merged queues to be then weight-raised, on queue splits,
even if low_latency is off. This commit addresses this problem by
adding the missing check.
Signed-off-by: Angelo Ruocco <angeloruocco90@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If two processes do I/O close to each other, then BFQ merges the
bfq_queues associated with these processes, to get a more sequential
I/O, and thus a higher throughput. In this respect, to detect whether
two processes are doing I/O close to each other, BFQ keeps a list of
the head-of-line I/O requests of all active bfq_queues. The list is
ordered by initial sectors, and implemented through a red-black tree
(rq_pos_tree).
Unfortunately, the update of the rq_pos_tree was incomplete, because
the tree was not updated on the removal of the head-of-line I/O
request of a bfq_queue, in case the queue did not remain empty. This
commit adds the missing update.
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Angelo Ruocco <angeloruocco90@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If two processes do I/O close to each other, i.e., are cooperating
processes in BFQ (and CFQ'S) nomenclature, then BFQ merges their
associated bfq_queues, so as to get sequential I/O from the union of
the I/O requests of the processes, and thus reach a higher
throughput. A merged queue is then split if its I/O stops being
sequential. In this respect, BFQ deems the I/O of a bfq_queue as
(mostly) sequential only if less than 4 I/O requests are random, out
of the last 32 requests inserted into the queue.
Unfortunately, extensive testing (with the interleaved_io benchmark of
the S suite [1], and with real applications spawning cooperating
processes) has clearly shown that, with such a low threshold, only a
rather low I/O throughput may be reached when several cooperating
processes do I/O. In particular, the outcome of each test run was
bimodal: if queue merging occurred and was stable during the test,
then the throughput was close to the peak rate of the storage device,
otherwise the throughput was arbitrarily low (usually around 1/10 of
the peak rate with a rotational device). The probability to get the
unlucky outcomes grew with the number of cooperating processes: it was
already significant with 5 processes, and close to one with 7 or more
processes.
The cause of the low throughput in the unlucky runs was that the
merged queues containing the I/O of these cooperating processes were
soon split, because they contained more random I/O requests than those
tolerated by the 4/32 threshold, but
- that I/O would have however allowed the storage device to reach
peak throughput or almost peak throughput;
- in contrast, the I/O of these processes, if served individually
(from separate queues) yielded a rather low throughput.
So we repeated our tests with increasing values of the threshold,
until we found the minimum value (19) for which we obtained maximum
throughput, reliably, with at least up to 9 cooperating
processes. Then we checked that the use of that higher threshold value
did not cause any regression for any other benchmark in the suite [1].
This commit raises the threshold to such a higher value.
[1] https://github.com/Algodev-github/S
Signed-off-by: Angelo Ruocco <angeloruocco90@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Introduce zone write locking to avoid write request reordering with
zoned block devices. This is achieved using a finer selection of the
next request to dispatch:
1) Any non-write request is always allowed to proceed.
2) Any write to a conventional zone is always allowed to proceed.
3) For a write to a sequential zone, the zone lock is first checked.
a) If the zone is not locked, the write is allowed to proceed after
its target zone is locked.
b) If the zone is locked, the write request is skipped and the next
request in the dispatch queue tested (back to step 1).
For a write request that has locked its target zone, the zone is
unlocked either when the request completes and the method
deadline_request_completed() is called, or when the request is requeued
using the method deadline_add_request().
Requests targeting a locked zone are always left in the scheduler queue
to preserve the initial write order. If no write request can be
dispatched, allow reads to be dispatched even if the write batch is not
done.
If the device used is not a zoned block device, or if zoned block device
support is disabled, this patch does not modify deadline behavior.
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
