For the normal WARN_ON() etc we added a print-the-modules-list already,
which is very useful to figure out candidates for certain types of bugs.
This patch adds the same print to the "scheduling while atomic" BUG warning,
for the same reason: when we get here it's very useful to see which modules
are loaded, to narrow down the candidate code list.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: mingo@elte.hu
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Fix this warning, which appears with !CONFIG_SMP:
kernel/sched.c:1216: warning: `init_hrtick' defined but not used
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Nothing really serious here, mainly just a matter of nit-picking :-/
From: Dmitry Adamushko <dmitry.adamushko@gmail.com>
For CONFIG_SCHED_DEBUG && CONFIG_SYSCT configs, sd->flags can be altered
while being manipulated in rebalance_domains(). Let's do an atomic check.
We rely here on the atomicity of read/write accesses for aligned words.
Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
The current code use a linear algorithm which causes scaling issues
on larger SMP machines. This patch replaces that algorithm with a
2-dimensional bitmap to reduce latencies in the wake-up path.
Signed-off-by: Gregory Haskins <ghaskins@novell.com>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
it is safe to ignore timers and flags when the feature is disabled.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Dmitry Adamushko pointed out a known flaw in the rt-balancing algorithm
that could allow suboptimal balancing if a non-migratable task gets
queued behind a running migratable one. It is discussed in this thread:
http://lkml.org/lkml/2008/4/22/296
This issue has been further exacerbated by a recent checkin to
sched-devel (git-id 5eee63a5ebc19a870ac40055c0be49457f3a89a3).
>From a pure priority standpoint, the run-queue is doing the "right"
thing. Using Dmitry's nomenclature, if T0 is on cpu1 first, and T1
wakes up at equal or lower priority (affined only to cpu1) later, it
*should* wait for T0 to finish. However, in reality that is likely
suboptimal from a system perspective if there are other cores that
could allow T0 and T1 to run concurrently. Since T1 can not migrate,
the only choice for higher concurrency is to try to move T0. This is
not something we addessed in the recent rt-balancing re-work.
This patch tries to enhance the balancing algorithm by accomodating this
scenario. It accomplishes this by incorporating the migratability of a
task into its priority calculation. Within a numerical tsk->prio, a
non-migratable task is logically higher than a migratable one. We
maintain this by introducing a new per-priority queue (xqueue, or
exclusive-queue) for holding non-migratable tasks. The scheduler will
draw from the xqueue over the standard shared-queue (squeue) when
available.
There are several details for utilizing this properly.
1) During task-wake-up, we not only need to check if the priority
preempts the current task, but we also need to check for this
non-migratable condition. Therefore, if a non-migratable task wakes
up and sees an equal priority migratable task already running, it
will attempt to preempt it *if* there is a likelyhood that the
current task will find an immediate home.
2) Tasks only get this non-migratable "priority boost" on wake-up. Any
requeuing will result in the non-migratable task being queued to the
end of the shared queue. This is an attempt to prevent the system
from being completely unfair to migratable tasks during things like
SCHED_RR timeslicing.
I am sure this patch introduces potentially "odd" behavior if you
concoct a scenario where a bunch of non-migratable threads could starve
migratable ones given the right pattern. I am not yet convinced that
this is a problem since we are talking about tasks of equal RT priority
anyway, and there never is much in the way of guarantees against
starvation under that scenario anyway. (e.g. you could come up with a
similar scenario with a specific timing environment verses an affinity
environment). I can be convinced otherwise, but for now I think this is
"ok".
Signed-off-by: Gregory Haskins <ghaskins@novell.com>
CC: Dmitry Adamushko <dmitry.adamushko@gmail.com>
CC: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Yanmin Zhang reported:
Comparing with 2.6.25, volanoMark has big regression with kernel 2.6.26-rc1.
It's about 50% on my 8-core stoakley, 16-core tigerton, and Itanium Montecito.
With bisect, I located the following patch:
| 18d95a2832 is first bad commit
| commit 18d95a2832
| Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
| Date: Sat Apr 19 19:45:00 2008 +0200
|
| sched: fair-group: SMP-nice for group scheduling
Revert it so that we get v2.6.25 behavior.
Bisected-by: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
As git-grep shows, open_softirq() is always called with the last argument
being NULL
block/blk-core.c: open_softirq(BLOCK_SOFTIRQ, blk_done_softirq, NULL);
kernel/hrtimer.c: open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq, NULL);
kernel/rcuclassic.c: open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL);
kernel/rcupreempt.c: open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL);
kernel/sched.c: open_softirq(SCHED_SOFTIRQ, run_rebalance_domains, NULL);
kernel/softirq.c: open_softirq(TASKLET_SOFTIRQ, tasklet_action, NULL);
kernel/softirq.c: open_softirq(HI_SOFTIRQ, tasklet_hi_action, NULL);
kernel/timer.c: open_softirq(TIMER_SOFTIRQ, run_timer_softirq, NULL);
net/core/dev.c: open_softirq(NET_TX_SOFTIRQ, net_tx_action, NULL);
net/core/dev.c: open_softirq(NET_RX_SOFTIRQ, net_rx_action, NULL);
This observation has already been made by Matthew Wilcox in June 2002
(http://www.cs.helsinki.fi/linux/linux-kernel/2002-25/0687.html)
"I notice that none of the current softirq routines use the data element
passed to them."
and the situation hasn't changed since them. So it appears we can safely
remove that extra argument to save 128 (54) bytes of kernel data (text).
Signed-off-by: Carlos R. Mafra <crmafra@ift.unesp.br>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Porting ftrace to the marker infrastructure.
Don't need to chain to the wakeup tracer from the sched tracer, because markers
support multiple probes connected.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Add preempt off timings. A lot of kernel core code is taken from the RT patch
latency trace that was written by Ingo Molnar.
This adds "preemptoff" and "preemptirqsoff" to /debugfs/tracing/available_tracers
Now instead of just tracing irqs off, preemption off can be selected
to be recorded.
When this is selected, it shares the same files as irqs off timings.
One can either trace preemption off, irqs off, or one or the other off.
By echoing "preemptoff" into /debugfs/tracing/current_tracer, recording
of preempt off only is performed. "irqsoff" will only record the time
irqs are disabled, but "preemptirqsoff" will take the total time irqs
or preemption are disabled. Runtime switching of these options is now
supported by simpling echoing in the appropriate trace name into
/debugfs/tracing/current_tracer.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
The tracer wants to be able to convert the state number
into a user visible character. This patch pulls that conversion
string out the scheduler into the header. This way if it were to
ever change, other parts of the kernel will know.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
add 3 lightweight callbacks to the tracer backend.
zero impact if tracing is turned off.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Change references from for_each_cpu_mask to for_each_cpu_mask_nr
where appropriate
Reviewed-by: Paul Jackson <pj@sgi.com>
Reviewed-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* Replace usages of MAX_NUMNODES with nr_node_ids in kernel/sched.c,
where appropriate. This saves some allocated space as well as many
wasted cycles going through node entries that are non-existent.
For inclusion into sched-devel/latest tree.
Based on:
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
+ sched-devel/latest .../mingo/linux-2.6-sched-devel.git
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Return type of cpu_rt_runtime_write() should be int instead of ssize_t.
Signed-off-by: Mirco Tischler <mt-ml@gmx.de>
Acked-by: Paul Menage <menage@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It acts exactly like a regular 'cond_resched()', but will not get
optimized away when CONFIG_PREEMPT is set.
Normal kernel code is already preemptable in the presense of
CONFIG_PREEMPT, so cond_resched() is optimized away (see commit
02b67cc3ba "sched: do not do
cond_resched() when CONFIG_PREEMPT").
But when wanting to conditionally reschedule while holding a lock, you
need to use "cond_sched_lock(lock)", and the new function is the BKL
equivalent of that.
Also make fs/locks.c use it.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The generic semaphore rewrite had a huge performance regression on AIM7
(and potentially other BKL-heavy benchmarks) because the generic
semaphores had been rewritten to be simple to understand and fair. The
latter, in particular, turns a semaphore-based BKL implementation into a
mess of scheduling.
The attempt to fix the performance regression failed miserably (see the
previous commit 00b41ec261 'Revert
"semaphore: fix"'), and so for now the simple and sane approach is to
instead just go back to the old spinlock-based BKL implementation that
never had any issues like this.
This patch also has the advantage of being reported to fix the
regression completely according to Yanmin Zhang, unlike the semaphore
hack which still left a couple percentage point regression.
As a spinlock, the BKL obviously has the potential to be a latency
issue, but it's not really any different from any other spinlock in that
respect. We do want to get rid of the BKL asap, but that has been the
plan for several years.
These days, the biggest users are in the tty layer (open/release in
particular) and Alan holds out some hope:
"tty release is probably a few months away from getting cured - I'm
afraid it will almost certainly be the very last user of the BKL in
tty to get fixed as it depends on everything else being sanely locked."
so while we're not there yet, we do have a plan of action.
Tested-by: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Alexander Viro <viro@ftp.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
this replaces the rq->clock stuff (and possibly cpu_clock()).
- architectures that have an 'imperfect' hardware clock can set
CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
- the 'jiffie' window might be superfulous when we update tick_gtod
before the __update_sched_clock() call in sched_clock_tick()
- cpu_clock() might be implemented as:
sched_clock_cpu(smp_processor_id())
if the accuracy proves good enough - how far can TSC drift in a
single jiffie when considering the filtering and idle hooks?
[ mingo@elte.hu: various fixes and cleanups ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
David Miller pointed it out that nothing in cpu_clock() sets
prev_cpu_time. This caused __sync_cpu_clock() to be called
all the time - against the intention of this code.
The result was that in practice we hit a global spinlock every
time cpu_clock() is called - which - even though cpu_clock()
is used for tracing and debugging, is suboptimal.
While at it, also:
- move the irq disabling to the outest layer,
this should make cpu_clock() warp-free when called with irqs
enabled.
- use long long instead of cycles_t - for platforms where cycles_t
is 32-bit.
Reported-by: David Miller <davem@davemloft.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When I echoed 0 into the "cpu.shares" file, a Div0 error occured.
We found it is caused by the following calling.
sched_group_set_shares(tg, shares)
set_se_shares(tg->se[i], shares/nr_cpu_ids)
__set_se_shares(se, shares)
div64_64((1ULL<<32), shares)
When the echoed value was less than the number of processores, the result of the
sentence "shares/nr_cpu_ids" was 0, and then the system called div64() to divide
the result, the Div0 error occured.
It is unnecessary that the shares value is divided by nr_cpu_ids, I think.
Because in the function __update_group_shares_cpu() and init_tg_cfs_entry(),
the shares value isn't divided by nr_cpu_ids when setting shares of the sched
entity.
This patch fixes this bug. And echoing ULONG_MAX value into cpu.shares also
causes Div0 error, so we set a macro MAX_SHARES to limit the max value of
shares.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Concurrent calls to detach_destroy_domains and arch_init_sched_domains
were prevented by the old scheduler subsystem cpu hotplug mutex. When
this got converted to get_online_cpus() the locking got broken.
Unlike before now several processes can concurrently enter the critical
sections that were protected by the old lock.
So use the already present doms_cur_mutex to protect these sections again.
Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
http://bugzilla.kernel.org/show_bug.cgi?id=10545
sched_stats.h says that __sched_info_switch is "called when prev !=
next" in the comment. sched.c should therefore do that.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Gautham R Shenoy reported:
> While running the usual CPU-Hotplug stress tests on linux-2.6.25,
> I noticed the following in the console logs.
>
> This is a wee bit difficult to reproduce. In the past 10 runs I hit this
> only once.
>
> ------------[ cut here ]------------
>
> WARNING: at kernel/sched.c:962 hrtick+0x2e/0x65()
>
> Just wondering if we are doing a good job at handling the cancellation
> of any per-cpu scheduler timers during CPU-Hotplug.
This looks like its indeed not cancelled at all and migrates the it to
another cpu. Fix it via a proper hotplug notifier mechanism.
Reported-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: stable@kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Noticed by sparse:
kernel/sched.c:760:20: warning: symbol 'sched_feat_names' was not declared. Should it be static?
kernel/sched.c:767:5: warning: symbol 'sched_feat_open' was not declared. Should it be static?
kernel/sched_fair.c:845:3: warning: returning void-valued expression
kernel/sched.c:4386:3: warning: returning void-valued expression
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Joel noticed that the !lw->inv_weight contition isn't unlikely anymore so
remove the unlikely annotation. Also, remove the two div64_u64() inv_weight
calculations, which makes them rely on the calc_delta_mine() path as well.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Joel Schopp <jschopp@austin.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Rename div64_64 to div64_u64 to make it consistent with the other divide
functions, so it clearly includes the type of the divide. Move its definition
to math64.h as currently no architecture overrides the generic implementation.
They can still override it of course, but the duplicated declarations are
avoided.
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Cc: Avi Kivity <avi@qumranet.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Patrick McHardy <kaber@trash.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This removes some filesystem boilerplate from the CFS cgroup subsystem.
Signed-off-by: Paul Menage <menage@google.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Several people have justifiably complained that the "_uint" suffix is
inappropriate for functions that handle u64 values, so this patch just renames
all these functions and their users to have the suffic _u64.
[peterz@infradead.org: build fix]
Signed-off-by: Paul Menage <menage@google.com>
Cc: "Li Zefan" <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "YAMAMOTO Takashi" <yamamoto@valinux.co.jp>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There is no guarantee that there is physical ram below 4GB, and in
fact many boxes don't have exactly that.
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
fix __aggregate_redistribute_shares() related lockup reported by
David S. Miller.
The problem this code tries to solve is 'accurately' calculating the 'fair'
share of the group weight for each cpu. The current code falls back to a global
group rebalance in case the sched_domain's span it looks at has no shares, but
does have tasks.
The reason it gets stuck here, is because its inherently racy - if someone
steals the last task after we compute the agg->rq_weight, but before we
rebalance, we'll never get out of the loop.
We could of course go fix that, but while looking at this issue I found that
this 'fallback' wasn't nearly as rare as I'd hoped it to be. In fact its quite
common - and given it walks the whole machine, thats very bad.
The new approach is simple (why didn't I think of it before?), we set the
aggregate shares to the full task group weight, and each larger sched domain
that encounters an aggregate shares larger than the weight, clips it (it
already re-distributes anyway).
This nicely converges to the desired global picture where the sum of all
shares equals the task group weight.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
A recent change prevents SGI Altix from booting.
This patch fixes the problem.
The regresson was introduced in commit 434d53b00d
Signed-off-by: Russ Anderson <rja@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Add missing kernel-doc in kernel/sched.c:
Warning(linux-2.6.25-git3//kernel/sched.c:7044): No description found for parameter 'span'
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
provide a text based interface to the scheduler features; this saves the
'user' from setting bits using decimal arithmetic.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
In order to level the hierarchy, we need to calculate load based on the
root view. That is, each task's load is in the same unit.
A
/ \
B 1
/ \
2 3
To compute 1's load we do:
weight(1)
--------------
rq_weight(A)
To compute 2's load we do:
weight(2) weight(B)
------------ * -----------
rq_weight(B) rw_weight(A)
This yields load fractions in comparable units.
The consequence is that it changes virtual time. We used to have:
time_{i}
vtime_{i} = ------------
weight_{i}
vtime = \Sum vtime_{i} = time / rq_weight.
But with the new way of load calculation we get that vtime equals time.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
De-couple load-balancing from the rb-trees, so that I can change their
organization.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Implement SMP nice support for the full group hierarchy.
On each load-balance action, compile a sched_domain wide view of the full
task_group tree. We compute the domain wide view when walking down the
hierarchy, and readjust the weights when walking back up.
After collecting and readjusting the domain wide view, we try to balance the
tasks within the task_groups. The current approach is a naively balance each
task group until we've moved the targeted amount of load.
Inspired by Srivatsa Vaddsgiri's previous code and Abhishek Chandra's H-SMP
paper.
XXX: there will be some numerical issues due to the limited nature of
SCHED_LOAD_SCALE wrt to representing a task_groups influence on the
total weight. When the tree is deep enough, or the task weight small
enough, we'll run out of bits.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Abhishek Chandra <chandra@cs.umn.edu>
CC: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
[rebased for sched-devel/latest]
- Add a new cpuset file, having levels:
sched_relax_domain_level
- Modify partition_sched_domains() and build_sched_domains()
to take attributes parameter passed from cpuset.
- Fill newidle_idx for node domains which currently unused but
might be required if sched_relax_domain_level become higher.
- We can change the default level by boot option 'relax_domain_level='.
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Add the full parent<->child relation thing into task_groups as well.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
UID grouping doesn't actually have a task_group representing the root of
the task_group tree. Add one.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch makes the group scheduler multi hierarchy aware.
[a.p.zijlstra@chello.nl: rt-parts and assorted fixes]
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch allows tasks and groups to exist in the same cfs_rq. With this
change the CFS group scheduling follows a 1/(M+N) model from a 1/(1+N)
fairness model where M tasks and N groups exist at the cfs_rq level.
[a.p.zijlstra@chello.nl: rt bits and assorted fixes]
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Add a new function that accepts a pointer to the "newly allowed cpus"
cpumask argument.
int set_cpus_allowed_ptr(struct task_struct *p, const cpumask_t *new_mask)
The current set_cpus_allowed() function is modified to use the above
but this does not result in an ABI change. And with some compiler
optimization help, it may not introduce any additional overhead.
Additionally, to enforce the read only nature of the new_mask arg, the
"const" property is migrated to sub-functions called by set_cpus_allowed.
This silences compiler warnings.
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Move the setting of nr_cpu_ids from sched_init() to start_kernel()
so that it's available as early as possible.
Note that an arch has the option of setting it even earlier if need be,
but it should not result in a different value than the setup_nr_cpu_ids()
function.
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Remove another cpumask_t variable from stack that was missed in the
last kernel_sched_c updates.
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Remove empty cpumask_t (and all non-zero/non-null) variables
in SD_*_INIT macros. Use memset(0) to clear. Also, don't
inline the initializer functions to save on stack space in
build_sched_domains().
* Merge change to include/linux/topology.h that uses the new
node_to_cpumask_ptr function in the nr_cpus_node macro into
this patch.
Depends on:
[mm-patch]: asm-generic-add-node_to_cpumask_ptr-macro.patch
[sched-devel]: sched: add new set_cpus_allowed_ptr function
Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Use new node_to_cpumask_ptr. This creates a pointer to the
cpumask for a given node. This definition is in mm patch:
asm-generic-add-node_to_cpumask_ptr-macro.patch
* Use new set_cpus_allowed_ptr function.
Depends on:
[mm-patch]: asm-generic-add-node_to_cpumask_ptr-macro.patch
[sched-devel]: sched: add new set_cpus_allowed_ptr function
[x86/latest]: x86: add cpus_scnprintf function
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Greg Banks <gnb@melbourne.sgi.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Modify sched_affinity functions to pass cpumask_t variables by reference
instead of by value.
* Use new set_cpus_allowed_ptr function.
Depends on:
[sched-devel]: sched: add new set_cpus_allowed_ptr function
Cc: Paul Jackson <pj@sgi.com>
Cc: Cliff Wickman <cpw@sgi.com>
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Modify cpuset_cpus_allowed to return the currently allowed cpuset
via a pointer argument instead of as the function return value.
* Use new set_cpus_allowed_ptr function.
* Cleanup CPU_MASK_ALL and NODE_MASK_ALL uses.
Depends on:
[sched-devel]: sched: add new set_cpus_allowed_ptr function
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Change fixed size arrays to per_cpu variables or dynamically allocated
arrays in sched_init() and sched_init_smp().
(1) static struct sched_entity *init_sched_entity_p[NR_CPUS];
(1) static struct cfs_rq *init_cfs_rq_p[NR_CPUS];
(1) static struct sched_rt_entity *init_sched_rt_entity_p[NR_CPUS];
(1) static struct rt_rq *init_rt_rq_p[NR_CPUS];
static struct sched_group **sched_group_nodes_bycpu[NR_CPUS];
(1) - these arrays are allocated via alloc_bootmem_low()
* Change sched_domain_debug_one() to use cpulist_scnprintf instead of
cpumask_scnprintf. This reduces the output buffer required and improves
readability when large NR_CPU count machines arrive.
* In sched_create_group() we allocate new arrays based on nr_cpu_ids.
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Currently the schedstats implementation does not allow the statistics
to be reset. This patch aims to allow that.
echo 0 > cpuacct.usage
resets the usage. Any other value is not allowed and returns -EINVAL.
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Change the variable names to the common convention for the cpuacct
subsystem.
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Currently the rt group scheduling does a per cpu runtime limit, however
the rt load balancer makes no guarantees about an equal spread of real-
time tasks, just that at any one time, the highest priority tasks run.
Solve this by making the runtime limit a global property by borrowing
excessive runtime from the other cpus once the local limit runs out.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Various SMP balancing algorithms require that the bandwidth period
run in sync.
Possible improvements are moving the rt_bandwidth thing into root_domain
and keeping a span per rt_bandwidth which marks throttled cpus.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
turn off sync wakeups by default. They are not needed anymore - the
buddy logic should be smart enough to keep the system from
overscheduling.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When using CONFIG_NO_HZ, rq->tick_timestamp is not updated every TICK_NSEC.
We check that the number of skipped ticks matches the clock jump seen in
__update_rq_clock().
Signed-off-by: Guillaume Chazarain <guichaz@yahoo.fr>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
kernel/sched.c:506: erreur: implicit declaration of function tick_get_tick_sched
kernel/sched.c:506: erreur: invalid type argument of ->
kernel/sched.c:506: erreur: NOHZ_MODE_INACTIVE undeclared (first use in this function)
kernel/sched.c:506: erreur: (Each undeclared identifier is reported only once
kernel/sched.c:506: erreur: for each function it appears in.)
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Alexey Zaytsev reported (and bisected) that the introduction of
cpu_clock() in printk made the timestamps jump back and forth.
Make cpu_clock() more reliable while still keeping it fast when it's
called frequently.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
add_timer_on() can add a timer on a CPU which is currently in a long
idle sleep, but the timer wheel is not reevaluated by the nohz code on
that CPU. So a timer can be delayed for quite a long time. This
triggered a false positive in the clocksource watchdog code.
To avoid this we need to wake up the idle CPU and enforce the
reevaluation of the timer wheel for the next timer event.
Add a function, which checks a given CPU for idle state, marks the
idle task with NEED_RESCHED and sends a reschedule IPI to notify the
other CPU of the change in the timer wheel.
Call this function from add_timer_on().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: stable@kernel.org
--
include/linux/sched.h | 6 ++++++
kernel/sched.c | 43 +++++++++++++++++++++++++++++++++++++++++++
kernel/timer.c | 10 +++++++++-
3 files changed, 58 insertions(+), 1 deletion(-)
Will be called each time the scheduling domains are rebuild.
Needed for architectures that don't have a static cpu topology.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Needed so it can be called from outside of sched.c.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
TREE_AVG and APPROX_AVG are initial task placement policies that have been
disabled for a long while.. time to remove them.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Wakeup-buddy tasks are cache-hot - this makes it a bit harder
for the load-balancer to tear them apart. (but it's still possible,
if the load is sufficiently assymetric)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
improve affine wakeups. Maintain the 'overlap' metric based on CFS's
sum_exec_runtime - which means the amount of time a task executes
after it wakes up some other task.
Use the 'overlap' for the wakeup decisions: if the 'overlap' is short,
it means there's strong workload coupling between this task and the
woken up task. If the 'overlap' is large then the workload is decoupled
and the scheduler will move them to separate CPUs more easily.
( Also slightly move the preempt_check within try_to_wake_up() - this has
no effect on functionality but allows 'early wakeups' (for still-on-rq
tasks) to be correctly accounted as well.)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Currently we schedule to the leftmost task in the runqueue. When the
runtimes are very short because of some server/client ping-pong,
especially in over-saturated workloads, this will cycle through all
tasks trashing the cache.
Reduce cache trashing by keeping dependent tasks together by running
newly woken tasks first. However, by not running the leftmost task first
we could starve tasks because the wakee can gain unlimited runtime.
Therefore we only run the wakee if its within a small
(wakeup_granularity) window of the leftmost task. This preserves
fairness, but does alternate server/client task groups.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Clear the cached inverse value when updating load. This is needed for
calc_delta_mine() to work correctly when using the rq load.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Fix a hard to trigger crash seen in the -rt kernel that also affects
the vanilla scheduler.
There is a race condition between schedule() and some dequeue/enqueue
functions; rt_mutex_setprio(), __setscheduler() and sched_move_task().
When scheduling to idle, idle_balance() is called to pull tasks from
other busy processor. It might drop the rq lock. It means that those 3
functions encounter on_rq=0 and running=1. The current task should be
put when running.
Here is a possible scenario:
CPU0 CPU1
| schedule()
| ->deactivate_task()
| ->idle_balance()
| -->load_balance_newidle()
rt_mutex_setprio() |
| --->double_lock_balance()
*get lock *rel lock
* on_rq=0, ruuning=1 |
* sched_class is changed |
*rel lock *get lock
: |
:
->put_prev_task_rt()
->pick_next_task_fair()
=> panic
The current process of CPU1(P1) is scheduling. Deactivated P1, and the
scheduler looks for another process on other CPU's runqueue because CPU1
will be idle. idle_balance(), load_balance_newidle() and
double_lock_balance() are called and double_lock_balance() could drop
the rq lock. On the other hand, CPU0 is trying to boost the priority of
P1. The result of boosting only P1's prio and sched_class are changed to
RT. The sched entities of P1 and P1's group are never put. It makes
cfs_rq invalid, because the cfs_rq has curr and no leaf, but
pick_next_task_fair() is called, then the kernel panics.
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
It is possible to allow the root-domain cache of online cpus to
become out of sync with the global cpu_online_map. This is because we
currently trigger removal of cpus too early in the notifier chain.
Other DOWN_PREPARE handlers may in fact run and reconfigure the
root-domain topology, thereby stomping on our own offline handling.
The end result is that rd->online may become out of sync with
cpu_online_map, which results in potential task misrouting.
So change the offline handling to be more tightly coupled with the
global offline process by triggering on CPU_DYING intead of
CPU_DOWN_PREPARE.
Signed-off-by: Gregory Haskins <ghaskins@novell.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We currently set the root-domain online span automatically when the
domain is added to the cpu if the cpu is already a member of
cpu_online_map.
This was done as a hack/bug-fix for s2ram, but it also causes a problem
with hotplug CPU_DOWN transitioning. The right way to fix the original
problem is to actually respond to CPU_UP events, instead of CPU_ONLINE,
which is already too late.
This solves the hung reboot regression reported by Andrew Morton and
others.
Signed-off-by: Gregory Haskins <ghaskins@novell.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch checks if we can set the rt_runtime_us to 0. If there is a
realtime task in the group, we don't want to set the rt_runtime_us as 0
or bad things will happen. (that task wont get any CPU time despite
being TASK_RUNNNG)
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
it was only possible to configure the rt-group scheduling parameters
beyond the default value in a very small range.
that's because div64_64() has a different calling convention than
do_div() :/
fix a few untidies while we are here; sysctl_sched_rt_period may overflow
due to that multiplication, so cast to u64 first. Also that RUNTIME_INF
juggling makes little sense although its an effective NOP.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Function sys_sched_rr_get_interval returns wrong time slice value for
SCHED_FIFO tasks. The time slice for SCHED_FIFO tasks should be 0.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Kei Tokunaga reported an interactivity problem when moving tasks
between control groups.
Tasks would retain their old vruntime when moved between groups, this
can cause funny lags. Re-set the vruntime on group move to fit within
the new tree.
Reported-by: Kei Tokunaga <tokunaga.keiich@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The following commits cause a number of regressions:
commit 58e2d4ca58
Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Date: Fri Jan 25 21:08:00 2008 +0100
sched: group scheduling, change how cpu load is calculated
commit 6b2d770026
Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Date: Fri Jan 25 21:08:00 2008 +0100
sched: group scheduler, fix fairness of cpu bandwidth allocation for task groups
Namely:
- very frequent wakeups on SMP, reported by PowerTop users.
- cacheline trashing on (large) SMP
- some latencies larger than 500ms
While there is a mergeable patch to fix the latter, the former issues
are not fixable in a manner suitable for .25 (we're at -rc3 now).
Hence we revert them and try again in v2.6.26.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Tested-by: Alexey Zaytsev <alexey.zaytsev@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Unsigned long values are always assigned to switch_count,
make it unsigned long.
kernel/sched.c:3897:15: warning: incorrect type in assignment (different signedness)
kernel/sched.c:3897:15: expected long *switch_count
kernel/sched.c:3897:15: got unsigned long *<noident>
kernel/sched.c:3921:16: warning: incorrect type in assignment (different signedness)
kernel/sched.c:3921:16: expected long *switch_count
kernel/sched.c:3921:16: got unsigned long *<noident>
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
do not call sched_clock() too early. Not only might rq->idle
not be set up - but pure per-cpu data might not be accessible
either.
this solves an ia64 early bootup hang with CONFIG_PRINTK_TIME=y.
Tested-by: Tony Luck <tony.luck@gmail.com>
Acked-by: Tony Luck <tony.luck@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Oleg Nesterov and others have pointed out that on some architectures,
the traditional sequence of
set_current_state(TASK_INTERRUPTIBLE);
if (CONDITION)
return;
schedule();
is racy wrt another CPU doing
CONDITION = 1;
wake_up_process(p);
because while set_current_state() has a memory barrier separating
setting of the TASK_INTERRUPTIBLE state from reading of the CONDITION
variable, there is no such memory barrier on the wakeup side.
Now, wake_up_process() does actually take a spinlock before it reads and
sets the task state on the waking side, and on x86 (and many other
architectures) that spinlock is in fact equivalent to a memory barrier,
but that is not generally guaranteed. The write that sets CONDITION
could move into the critical region protected by the runqueue spinlock.
However, adding a smp_wmb() to before the spinlock should now order the
writing of CONDITION wrt the lock itself, which in turn is ordered wrt
the accesses within the spinlock (which includes the reading of the old
state).
This should thus close the race (which probably has never been seen in
practice, but since smp_wmb() is a no-op on x86, it's not like this will
make anything worse either on the most common architecture where the
spinlock already gave the required protection).
Acked-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Kprobes makes use of preempt_disable(),preempt_enable_noresched() and these
functions inturn call add/sub_preempt_count(). So we need to refuse user from
inserting probe in to these functions.
This patch disallows user from probing add/sub_preempt_count().
Signed-off-by: Srinivasa DS <srinivasa@in.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Refuse to accept or create RT tasks in groups that can't run them.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Clean up some of the excessive ifdeffery introduces in the last patch.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Make the rt group scheduler compile time configurable.
Keep it experimental for now.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Change the rt_ratio interface to rt_runtime_us, to match rt_period_us.
This avoids picking a granularity for the ratio.
Extend the /sys/kernel/uids/<uid>/ interface to allow setting
the group's rt_runtime.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Steven mentioned the fun case where a lock holding task will be throttled.
Simple fix: allow groups that have boosted tasks to run anyway.
If a runnable task in a throttled group gets boosted the dequeue/enqueue
done by rt_mutex_setprio() is enough to unthrottle the group.
This is ofcourse not quite correct. Two possible ways forward are:
- second prio array for boosted tasks
- boost to a prio ceiling (this would also work for deadline scheduling)
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
lockdep spotted this bogus irq locking. normalize_rt_tasks() can be called
from hardirq context through sysrq-n
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* 'task_killable' of git://git.kernel.org/pub/scm/linux/kernel/git/willy/misc: (22 commits)
Remove commented-out code copied from NFS
NFS: Switch from intr mount option to TASK_KILLABLE
Add wait_for_completion_killable
Add wait_event_killable
Add schedule_timeout_killable
Use mutex_lock_killable in vfs_readdir
Add mutex_lock_killable
Use lock_page_killable
Add lock_page_killable
Add fatal_signal_pending
Add TASK_WAKEKILL
exit: Use task_is_*
signal: Use task_is_*
sched: Use task_contributes_to_load, TASK_ALL and TASK_NORMAL
ptrace: Use task_is_*
power: Use task_is_*
wait: Use TASK_NORMAL
proc/base.c: Use task_is_*
proc/array.c: Use TASK_REPORT
perfmon: Use task_is_*
...
Fixed up conflicts in NFS/sunrpc manually..
This removes the extra struct task_struct *p parameter in inc_nr_running
and dec_nr_running functions.
Signed-off by: Jerry Stralko <gerb.stralko@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The break_lock data structure and code for spinlocks is quite nasty.
Not only does it double the size of a spinlock but it changes locking to
a potentially less optimal trylock.
Put all of that under CONFIG_GENERIC_LOCKBREAK, and introduce a
__raw_spin_is_contended that uses the lock data itself to determine whether
there are waiters on the lock, to be used if CONFIG_GENERIC_LOCKBREAK is
not set.
Rename need_lockbreak to spin_needbreak, make it use spin_is_contended to
decouple it from the spinlock implementation, and make it typesafe (rwlocks
do not have any need_lockbreak sites -- why do they even get bloated up
with that break_lock then?).
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
The attached patch is something really simple that can sometimes help
in getting more info out of a hung system.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
sched: fix rq->clock warps on frequency changes
Fix 2bacec8c31
(sched: touch softlockup watchdog after idling) that reintroduced warps
on frequency changes. touch_softlockup_watchdog() calls __update_rq_clock
that checks rq->clock for warps, so call it after adjusting rq->clock.
Signed-off-by: Guillaume Chazarain <guichaz@yahoo.fr>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We need to teach no_hz about the rt throttling because its tick driven.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Extend group scheduling to also cover the realtime classes. It uses the time
limiting introduced by the previous patch to allow multiple realtime groups.
The hard time limit is required to keep behaviour deterministic.
The algorithms used make the realtime scheduler O(tg), linear scaling wrt the
number of task groups. This is the worst case behaviour I can't seem to get out
of, the avg. case of the algorithms can be improved, I focused on correctness
and worst case.
[ akpm@linux-foundation.org: move side-effects out of BUG_ON(). ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Very simple time limit on the realtime scheduling classes.
Allow the rq's realtime class to consume sched_rt_ratio of every
sched_rt_period slice. If the class exceeds this quota the fair class
will preempt the realtime class.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Use HR-timers (when available) to deliver an accurate preemption tick.
The regular scheduler tick that runs at 1/HZ can be too coarse when nice
level are used. The fairness system will still keep the cpu utilisation 'fair'
by then delaying the task that got an excessive amount of CPU time but try to
minimize this by delivering preemption points spot-on.
The average frequency of this extra interrupt is sched_latency / nr_latency.
Which need not be higher than 1/HZ, its just that the distribution within the
sched_latency period is important.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Why do we even have cond_resched when real preemption
is on? It seems to be a waste of space and time.
remove cond_resched with CONFIG_PREEMPT on.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Move the task_struct members specific to rt scheduling together.
A future optimization could be to put sched_entity and sched_rt_entity
into a union.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The baseline code statically builds the span maps when the domain is formed.
Previous attempts at dynamically updating the maps caused a suspend-to-ram
regression, which should now be fixed.
Signed-off-by: Gregory Haskins <ghaskins@novell.com>
CC: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Dmitry Adamushko found that the current implementation of the RT
balancing code left out changes to the sched_setscheduler and
rt_mutex_setprio.
This patch addresses this issue by adding methods to the schedule classes
to handle being switched out of (switched_from) and being switched into
(switched_to) a sched_class. Also a method for changing of priorities
is also added (prio_changed).
This patch also removes some duplicate logic between rt_mutex_setprio and
sched_setscheduler.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
To make the main sched.c code more agnostic to the schedule classes.
Instead of having specific hooks in the schedule code for the RT class
balancing. They are replaced with a pre_schedule, post_schedule
and task_wake_up methods. These methods may be used by any of the classes
but currently, only the sched_rt class implements them.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Clean-up try_to_wake_up().
Get rid of the 'new_cpu' variable in try_to_wake_up() [ that's, one
#ifdef section less ]. Also remove a few redundant blank lines.
Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
style cleanup of various changes that were done recently.
no code changed:
text data bss dec hex filename
26399 2578 48 29025 7161 sched.o.before
26399 2578 48 29025 7161 sched.o.after
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We move the rt-overload data as the first global to per-domain
reclassification. This limits the scope of overload related cache-line
bouncing to stay with a specified partition instead of affecting all
cpus in the system.
Finally, we limit the scope of find_lowest_cpu searches to the domain
instead of the entire system. Note that we would always respect domain
boundaries even without this patch, but we first would scan potentially
all cpus before whittling the list down. Now we can avoid looking at
RQs that are out of scope, again reducing cache-line hits.
Note: In some cases, task->cpus_allowed will effectively reduce our search
to within our domain. However, I believe there are cases where the
cpus_allowed mask may be all ones and therefore we err on the side of
caution. If it can be optimized later, so be it.
Signed-off-by: Gregory Haskins <ghaskins@novell.com>
CC: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We add the notion of a root-domain which will be used later to rescope
global variables to per-domain variables. Each exclusive cpuset
essentially defines an island domain by fully partitioning the member cpus
from any other cpuset. However, we currently still maintain some
policy/state as global variables which transcend all cpusets. Consider,
for instance, rt-overload state.
Whenever a new exclusive cpuset is created, we also create a new
root-domain object and move each cpu member to the root-domain's span.
By default the system creates a single root-domain with all cpus as
members (mimicking the global state we have today).
We add some plumbing for storing class specific data in our root-domain.
Whenever a RQ is switching root-domains (because of repartitioning) we
give each sched_class the opportunity to remove any state from its old
domain and add state to the new one. This logic doesn't have any clients
yet but it will later in the series.
Signed-off-by: Gregory Haskins <ghaskins@novell.com>
CC: Christoph Lameter <clameter@sgi.com>
CC: Paul Jackson <pj@sgi.com>
CC: Simon Derr <simon.derr@bull.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We have logic to detect whether the system has migratable tasks, but we are
not using it when deciding whether to push tasks away. So we add support
for considering this new information.
Signed-off-by: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The current wake-up code path tries to determine if it can optimize the
wake-up to "this_cpu" by computing load calculations. The problem is that
these calculations are only relevant to SCHED_OTHER tasks where load is king.
For RT tasks, priority is king. So the load calculation is completely wasted
bandwidth.
Therefore, we create a new sched_class interface to help with
pre-wakeup routing decisions and move the load calculation as a function
of CFS task's class.
Signed-off-by: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Some RT tasks (particularly kthreads) are bound to one specific CPU.
It is fairly common for two or more bound tasks to get queued up at the
same time. Consider, for instance, softirq_timer and softirq_sched. A
timer goes off in an ISR which schedules softirq_thread to run at RT50.
Then the timer handler determines that it's time to smp-rebalance the
system so it schedules softirq_sched to run. So we are in a situation
where we have two RT50 tasks queued, and the system will go into
rt-overload condition to request other CPUs for help.
This causes two problems in the current code:
1) If a high-priority bound task and a low-priority unbounded task queue
up behind the running task, we will fail to ever relocate the unbounded
task because we terminate the search on the first unmovable task.
2) We spend precious futile cycles in the fast-path trying to pull
overloaded tasks over. It is therefore optimial to strive to avoid the
overhead all together if we can cheaply detect the condition before
overload even occurs.
This patch tries to achieve this optimization by utilizing the hamming
weight of the task->cpus_allowed mask. A weight of 1 indicates that
the task cannot be migrated. We will then utilize this information to
skip non-migratable tasks and to eliminate uncessary rebalance attempts.
We introduce a per-rq variable to count the number of migratable tasks
that are currently running. We only go into overload if we have more
than one rt task, AND at least one of them is migratable.
In addition, we introduce a per-task variable to cache the cpus_allowed
weight, since the hamming calculation is probably relatively expensive.
We only update the cached value when the mask is updated which should be
relatively infrequent, especially compared to scheduling frequency
in the fast path.
Signed-off-by: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch adds pushing of overloaded RT tasks from a runqueue that is
having tasks (most likely RT tasks) added to the run queue.
TODO: We don't cover the case of waking of new RT tasks (yet).
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch adds the algorithm to pull tasks from RT overloaded runqueues.
When a pull RT is initiated, all overloaded runqueues are examined for
a RT task that is higher in prio than the highest prio task queued on the
target runqueue. If another runqueue holds a RT task that is of higher
prio than the highest prio task on the target runqueue is found it is pulled
to the target runqueue.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch adds an algorithm to push extra RT tasks off a run queue to
other CPU runqueues.
When more than one RT task is added to a run queue, this algorithm takes
an assertive approach to push the RT tasks that are not running onto other
run queues that have lower priority. The way this works is that the highest
RT task that is not running is looked at and we examine the runqueues on
the CPUS for that tasks affinity mask. We find the runqueue with the lowest
prio in the CPU affinity of the picked task, and if it is lower in prio than
the picked task, we push the task onto that CPU runqueue.
We continue pushing RT tasks off the current runqueue until we don't push any
more. The algorithm stops when the next highest RT task can't preempt any
other processes on other CPUS.
TODO: The algorithm may stop when there are still RT tasks that can be
migrated. Specifically, if the highest non running RT task CPU affinity
is restricted to CPUs that are running higher priority tasks, there may
be a lower priority task queued that has an affinity with a CPU that is
running a lower priority task that it could be migrated to. This
patch set does not address this issue.
Note: checkpatch reveals two over 80 character instances. I'm not sure
that breaking them up will help visually, so I left them as is.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch adds accounting to each runqueue to keep track of the
highest prio task queued on the run queue. We only care about
RT tasks, so if the run queue does not contain any active RT tasks
its priority will be considered MAX_RT_PRIO.
This information will be used for later patches.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch adds accounting to keep track of the number of RT tasks running
on a runqueue. This information will be used in later patches.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
this patch extends the soft-lockup detector to automatically
detect hung TASK_UNINTERRUPTIBLE tasks. Such hung tasks are
printed the following way:
------------------>
INFO: task prctl:3042 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message
prctl D fd5e3793 0 3042 2997
f6050f38 00000046 00000001 fd5e3793 00000009 c06d8264 c06dae80 00000286
f6050f40 f6050f00 f7d34d90 f7d34fc8 c1e1be80 00000001 f6050000 00000000
f7e92d00 00000286 f6050f18 c0489d1a f6050f40 00006605 00000000 c0133a5b
Call Trace:
[<c04883a5>] schedule_timeout+0x6d/0x8b
[<c04883d8>] schedule_timeout_uninterruptible+0x15/0x17
[<c0133a76>] msleep+0x10/0x16
[<c0138974>] sys_prctl+0x30/0x1e2
[<c0104c52>] sysenter_past_esp+0x5f/0xa5
=======================
2 locks held by prctl/3042:
#0: (&sb->s_type->i_mutex_key#5){--..}, at: [<c0197d11>] do_fsync+0x38/0x7a
#1: (jbd_handle){--..}, at: [<c01ca3d2>] journal_start+0xc7/0xe9
<------------------
the current default timeout is 120 seconds. Such messages are printed
up to 10 times per bootup. If the system has crashed already then the
messages are not printed.
if lockdep is enabled then all held locks are printed as well.
this feature is a natural extension to the softlockup-detector (kernel
locked up without scheduling) and to the NMI watchdog (kernel locked up
with IRQs disabled).
[ Gautham R Shenoy <ego@in.ibm.com>: CPU hotplug fixes. ]
[ Andrew Morton <akpm@linux-foundation.org>: build warning fix. ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
This patch converts the known per-subsystem mutexes to get_online_cpus
put_online_cpus. It also eliminates the CPU_LOCK_ACQUIRE and
CPU_LOCK_RELEASE hotplug notification events.
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
