| Commit message (Collapse) | Author | Age |
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This task is preparatory for the migrate_disable() implementation, but
stands on its own and provides a cleanup.
It currently only converts those sites required for task-placement.
Kosaki-san once mentioned replacing cpus_allowed with a proper
cpumask_t instead of the NR_CPUS sized array it currently is, that
would also require something like this.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Link: http://lkml.kernel.org/n/tip-e42skvaddos99psip0vce41o@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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rq's idle_at_tick is set to idle/busy during the timer tick
depending on the cpu was idle or not. This will be used later in the load
balance that will be done in the softirq context (which is a process
context in -RT kernels).
For nohz kernels, for the cpu doing nohz idle load balance on behalf of
all the idle cpu's, its rq->idle_at_tick might have a stale value (which is
recorded when it got the timer tick presumably when it is busy).
As the nohz idle load balancing is also being done at the same place
as the regular load balancing, nohz idle load balancing was bailing out
when it sees rq's idle_at_tick not set.
Thus leading to poor system utilization.
Rename rq's idle_at_tick to idle_balance and set it when someone requests
for nohz idle balance on an idle cpu.
Reported-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20111003220934.892350549@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Current use of smp call function to kick the nohz idle balance can deadlock
in this scenario.
1. cpu-A did a generic_exec_single() to cpu-B and after queuing its call single
data (csd) to the call single queue, cpu-A took a timer interrupt. Actual IPI
to cpu-B to process the call single queue is not yet sent.
2. As part of the timer interrupt handler, cpu-A decided to kick cpu-B
for the idle load balancing (sets cpu-B's rq->nohz_balance_kick to 1)
and __smp_call_function_single() with nowait will queue the csd to the
cpu-B's queue. But the generic_exec_single() won't send an IPI to cpu-B
as the call single queue was not empty.
3. cpu-A is busy with lot of interrupts
4. Meanwhile cpu-B is entering and exiting idle and noticed that it has
it's rq->nohz_balance_kick set to '1'. So it will go ahead and do the
idle load balancer and clear its rq->nohz_balance_kick.
5. At this point, csd queued as part of the step-2 above is still locked
and waiting to be serviced on cpu-B.
6. cpu-A is still busy with interrupt load and now it got another timer
interrupt and as part of it decided to kick cpu-B for another idle load
balancing (as it finds cpu-B's rq->nohz_balance_kick cleared in step-4
above) and does __smp_call_function_single() with the same csd that is
still locked.
7. And we get a deadlock waiting for the csd_lock() in the
__smp_call_function_single().
Main issue here is that cpu-B can service the idle load balancer kick
request from cpu-A even with out receiving the IPI and this lead to
doing multiple __smp_call_function_single() on the same csd leading to
deadlock.
To kick a cpu, scheduler already has the reschedule vector reserved. Use
that mechanism (kick_process()) instead of using the generic smp call function
mechanism to kick off the nohz idle load balancing and avoid the deadlock.
[ This issue is present from 2.6.35+ kernels, but marking it -stable
only from v3.0+ as the proposed fix depends on the scheduler_ipi()
that is introduced recently. ]
Reported-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: stable@kernel.org # v3.0+
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20111003220934.834943260@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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On -rt we observed hackbench waking all 400 tasks to a single cpu.
This is because of select_idle_sibling()'s interaction with the new
ipi based wakeup scheme.
The existing idle_cpu() test only checks to see if the current task on
that cpu is the idle task, it does not take already queued tasks into
account, nor does it take queued to be woken tasks into account.
If the remote wakeup IPIs come hard enough, there won't be time to
schedule away from the idle task, and would thus keep thinking the cpu
was in fact idle, regardless of the fact that there were already
several hundred tasks runnable.
We couldn't reproduce on mainline, but there's no reason it couldn't
happen.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-3o30p18b2paswpc9ohy2gltp@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Use the generic llist primitives.
We had a private lockless list implementation in the scheduler in the wake-list
code, now that we have a generic llist implementation that provides all required
operations, switch to it.
This patch is not expected to change any behavior.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1315836353.26517.42.camel@twins
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Merge reason: pick up the latest fixes.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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David reported:
Attached below is a watered-down version of rt/tst-cpuclock2.c from
GLIBC. Just build it with "gcc -o test test.c -lpthread -lrt" or
similar.
Run it several times, and you will see cases where the main thread
will measure a process clock difference before and after the nanosleep
which is smaller than the cpu-burner thread's individual thread clock
difference. This doesn't make any sense since the cpu-burner thread
is part of the top-level process's thread group.
I've reproduced this on both x86-64 and sparc64 (using both 32-bit and
64-bit binaries).
For example:
[davem@boricha build-x86_64-linux]$ ./test
process: before(0.001221967) after(0.498624371) diff(497402404)
thread: before(0.000081692) after(0.498316431) diff(498234739)
self: before(0.001223521) after(0.001240219) diff(16698)
[davem@boricha build-x86_64-linux]$
The diff of 'process' should always be >= the diff of 'thread'.
I make sure to wrap the 'thread' clock measurements the most tightly
around the nanosleep() call, and that the 'process' clock measurements
are the outer-most ones.
---
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include <pthread.h>
static pthread_barrier_t barrier;
static void *chew_cpu(void *arg)
{
pthread_barrier_wait(&barrier);
while (1)
__asm__ __volatile__("" : : : "memory");
return NULL;
}
int main(void)
{
clockid_t process_clock, my_thread_clock, th_clock;
struct timespec process_before, process_after;
struct timespec me_before, me_after;
struct timespec th_before, th_after;
struct timespec sleeptime;
unsigned long diff;
pthread_t th;
int err;
err = clock_getcpuclockid(0, &process_clock);
if (err)
return 1;
err = pthread_getcpuclockid(pthread_self(), &my_thread_clock);
if (err)
return 1;
pthread_barrier_init(&barrier, NULL, 2);
err = pthread_create(&th, NULL, chew_cpu, NULL);
if (err)
return 1;
err = pthread_getcpuclockid(th, &th_clock);
if (err)
return 1;
pthread_barrier_wait(&barrier);
err = clock_gettime(process_clock, &process_before);
if (err)
return 1;
err = clock_gettime(my_thread_clock, &me_before);
if (err)
return 1;
err = clock_gettime(th_clock, &th_before);
if (err)
return 1;
sleeptime.tv_sec = 0;
sleeptime.tv_nsec = 500000000;
nanosleep(&sleeptime, NULL);
err = clock_gettime(th_clock, &th_after);
if (err)
return 1;
err = clock_gettime(my_thread_clock, &me_after);
if (err)
return 1;
err = clock_gettime(process_clock, &process_after);
if (err)
return 1;
diff = process_after.tv_nsec - process_before.tv_nsec;
printf("process: before(%lu.%.9lu) after(%lu.%.9lu) diff(%lu)\n",
process_before.tv_sec, process_before.tv_nsec,
process_after.tv_sec, process_after.tv_nsec, diff);
diff = th_after.tv_nsec - th_before.tv_nsec;
printf("thread: before(%lu.%.9lu) after(%lu.%.9lu) diff(%lu)\n",
th_before.tv_sec, th_before.tv_nsec,
th_after.tv_sec, th_after.tv_nsec, diff);
diff = me_after.tv_nsec - me_before.tv_nsec;
printf("self: before(%lu.%.9lu) after(%lu.%.9lu) diff(%lu)\n",
me_before.tv_sec, me_before.tv_nsec,
me_after.tv_sec, me_after.tv_nsec, diff);
return 0;
}
This is due to us using p->se.sum_exec_runtime in
thread_group_cputime() where we iterate the thread group and sum all
data. This does not take time since the last schedule operation (tick
or otherwise) into account. We can cure this by using
task_sched_runtime() at the cost of having to take locks.
This also means we can (and must) do away with
thread_group_sched_runtime() since the modified thread_group_cputime()
is now more accurate and would deadlock when called from
thread_group_sched_runtime().
Aside of that it makes the function safe on 32 bit systems. The old
code added t->se.sum_exec_runtime unprotected. sum_exec_runtime is a
64bit value and could be changed on another cpu at the same time.
Reported-by: David Miller <davem@davemloft.net>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: stable@kernel.org
Link: http://lkml.kernel.org/r/1314874459.7945.22.camel@twins
Tested-by: David Miller <davem@davemloft.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Commit c259e01a1ec ("sched: Separate the scheduler entry for
preemption") contained a boo-boo wrecking wchan output. It forgot to
put the new schedule() function in the __sched section and thereby
doesn't get properly ignored for things like wchan.
Tested-by: Simon Kirby <sim@hostway.ca>
Cc: stable@kernel.org # 2.6.39+
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110923000346.GA25425@hostway.ca
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Merge reason: We are queueing up a dependent patch.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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* 'sched-fixes-for-linus' of git://tesla.tglx.de/git/linux-2.6-tip:
sched: Fix a memory leak in __sdt_free()
sched: Move blk_schedule_flush_plug() out of __schedule()
sched: Separate the scheduler entry for preemption
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This patch fixes the following memory leak:
unreferenced object 0xffff880107266800 (size 512):
comm "sched-powersave", pid 3718, jiffies 4323097853 (age 27495.450s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<ffffffff81133940>] create_object+0x187/0x28b
[<ffffffff814ac103>] kmemleak_alloc+0x73/0x98
[<ffffffff811232ba>] __kmalloc_node+0x104/0x159
[<ffffffff81044b98>] kzalloc_node.clone.97+0x15/0x17
[<ffffffff8104cb90>] build_sched_domains+0xb7/0x7f3
[<ffffffff8104d4df>] partition_sched_domains+0x1db/0x24a
[<ffffffff8109ee4a>] do_rebuild_sched_domains+0x3b/0x47
[<ffffffff810a00c7>] rebuild_sched_domains+0x10/0x12
[<ffffffff8104d5ba>] sched_power_savings_store+0x6c/0x7b
[<ffffffff8104d5df>] sched_mc_power_savings_store+0x16/0x18
[<ffffffff8131322c>] sysdev_class_store+0x20/0x22
[<ffffffff81193876>] sysfs_write_file+0x108/0x144
[<ffffffff81135b10>] vfs_write+0xaf/0x102
[<ffffffff81135d23>] sys_write+0x4d/0x74
[<ffffffff814c8a42>] system_call_fastpath+0x16/0x1b
[<ffffffffffffffff>] 0xffffffffffffffff
Signed-off-by: WANG Cong <amwang@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: stable@kernel.org # 3.0
Link: http://lkml.kernel.org/r/1313671017-4112-1-git-send-email-amwang@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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There is no real reason to run blk_schedule_flush_plug() with
interrupts and preemption disabled.
Move it into schedule() and call it when the task is going voluntarily
to sleep. There might be false positives when the task is woken
between that call and actually scheduling, but that's not really
different from being woken immediately after switching away.
This fixes a deadlock in the scheduler where the
blk_schedule_flush_plug() callchain enables interrupts and thereby
allows a wakeup to happen of the task that's going to sleep.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@kernel.org # 2.6.39+
Link: http://lkml.kernel.org/n/tip-dwfxtra7yg1b5r65m32ywtct@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Block-IO and workqueues call into notifier functions from the
scheduler core code with interrupts and preemption disabled. These
calls should be made before entering the scheduler core.
To simplify this, separate the scheduler core code into
__schedule(). __schedule() is directly called from the places which
set PREEMPT_ACTIVE and from schedule(). This allows us to add the work
checks into schedule(), so they are only called when a task voluntary
goes to sleep.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@kernel.org # 2.6.39+
Link: http://lkml.kernel.org/r/20110622174918.813258321@linutronix.de
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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The current cgroup context switch code was incorrect leading
to bogus counts. Furthermore, as soon as there was an active
cgroup event on a CPU, the context switch cost on that CPU
would increase by a significant amount as demonstrated by a
simple ping/pong example:
$ ./pong
Both processes pinned to CPU1, running for 10s
10684.51 ctxsw/s
Now start a cgroup perf stat:
$ perf stat -e cycles,cycles -A -a -G test -C 1 -- sleep 100
$ ./pong
Both processes pinned to CPU1, running for 10s
6674.61 ctxsw/s
That's a 37% penalty.
Note that pong is not even in the monitored cgroup.
The results shown by perf stat are bogus:
$ perf stat -e cycles,cycles -A -a -G test -C 1 -- sleep 100
Performance counter stats for 'sleep 100':
CPU1 <not counted> cycles test
CPU1 16,984,189,138 cycles # 0.000 GHz
The second 'cycles' event should report a count @ CPU clock
(here 2.4GHz) as it is counting across all cgroups.
The patch below fixes the bogus accounting and bypasses any
cgroup switches in case the outgoing and incoming tasks are
in the same cgroup.
With this patch the same test now yields:
$ ./pong
Both processes pinned to CPU1, running for 10s
10775.30 ctxsw/s
Start perf stat with cgroup:
$ perf stat -e cycles,cycles -A -a -G test -C 1 -- sleep 10
Run pong outside the cgroup:
$ /pong
Both processes pinned to CPU1, running for 10s
10687.80 ctxsw/s
The penalty is now less than 2%.
And the results for perf stat are correct:
$ perf stat -e cycles,cycles -A -a -G test -C 1 -- sleep 10
Performance counter stats for 'sleep 10':
CPU1 <not counted> cycles test # 0.000 GHz
CPU1 23,933,981,448 cycles # 0.000 GHz
Now perf stat reports the correct counts for
for the non cgroup event.
If we run pong inside the cgroup, then we also get the
correct counts:
$ perf stat -e cycles,cycles -A -a -G test -C 1 -- sleep 10
Performance counter stats for 'sleep 10':
CPU1 22,297,726,205 cycles test # 0.000 GHz
CPU1 23,933,981,448 cycles # 0.000 GHz
10.001457237 seconds time elapsed
Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110825135803.GA4697@quad
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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When a local cfs_rq blocks we return the majority of its remaining quota to the
global bandwidth pool for use by other runqueues.
We do this only when the quota is current and there is more than
min_cfs_rq_quota [1ms by default] of runtime remaining on the rq.
In the case where there are throttled runqueues and we have sufficient
bandwidth to meter out a slice, a second timer is kicked off to handle this
delivery, unthrottling where appropriate.
Using a 'worst case' antagonist which executes on each cpu
for 1ms before moving onto the next on a fairly large machine:
no quota generations:
197.47 ms /cgroup/a/cpuacct.usage
199.46 ms /cgroup/a/cpuacct.usage
205.46 ms /cgroup/a/cpuacct.usage
198.46 ms /cgroup/a/cpuacct.usage
208.39 ms /cgroup/a/cpuacct.usage
Since we are allowed to use "stale" quota our usage is effectively bounded by
the rate of input into the global pool and performance is relatively stable.
with quota generations [1s increments]:
119.58 ms /cgroup/a/cpuacct.usage
119.65 ms /cgroup/a/cpuacct.usage
119.64 ms /cgroup/a/cpuacct.usage
119.63 ms /cgroup/a/cpuacct.usage
119.60 ms /cgroup/a/cpuacct.usage
The large deficit here is due to quota generations (/intentionally/) preventing
us from now using previously stranded slack quota. The cost is that this quota
becomes unavailable.
with quota generations and quota return:
200.09 ms /cgroup/a/cpuacct.usage
200.09 ms /cgroup/a/cpuacct.usage
198.09 ms /cgroup/a/cpuacct.usage
200.09 ms /cgroup/a/cpuacct.usage
200.06 ms /cgroup/a/cpuacct.usage
By returning unused quota we're able to both stably consume our desired quota
and prevent unintentional overages due to the abuse of slack quota from
previous quota periods (especially on a large machine).
Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184758.306848658@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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This change introduces statistics exports for the cpu sub-system, these are
added through the use of a stat file similar to that exported by other
subsystems.
The following exports are included:
nr_periods: number of periods in which execution occurred
nr_throttled: the number of periods above in which execution was throttle
throttled_time: cumulative wall-time that any cpus have been throttled for
this group
Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Nikhil Rao <ncrao@google.com>
Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184758.198901931@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Throttled tasks are invisisble to cpu-offline since they are not eligible for
selection by pick_next_task(). The regular 'escape' path for a thread that is
blocked at offline is via ttwu->select_task_rq, however this will not handle a
throttled group since there are no individual thread wakeups on an unthrottle.
Resolve this by unthrottling offline cpus so that threads can be migrated.
Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184757.989000590@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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From the perspective of load-balance and shares distribution, throttled
entities should be invisible.
However, both of these operations work on 'active' lists and are not
inherently aware of what group hierarchies may be present. In some cases this
may be side-stepped (e.g. we could sideload via tg_load_down in load balance)
while in others (e.g. update_shares()) it is more difficult to compute without
incurring some O(n^2) costs.
Instead, track hierarchicaal throttled state at time of transition. This
allows us to easily identify whether an entity belongs to a throttled hierarchy
and avoid incorrect interactions with it.
Also, when an entity leaves a throttled hierarchy we need to advance its
time averaging for shares averaging so that the elapsed throttled time is not
considered as part of the cfs_rq's operation.
We also use this information to prevent buddy interactions in the wakeup and
yield_to() paths.
Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184757.777916795@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Extend walk_tg_tree to accept a positional argument
static int walk_tg_tree_from(struct task_group *from,
tg_visitor down, tg_visitor up, void *data)
Existing semantics are preserved, caller must hold rcu_lock() or sufficient
analogue.
Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184757.677889157@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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At the start of each period we refresh the global bandwidth pool. At this time
we must also unthrottle any cfs_rq entities who are now within bandwidth once
more (as quota permits).
Unthrottled entities have their corresponding cfs_rq->throttled flag cleared
and their entities re-enqueued.
Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184757.574628950@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Now that consumption is tracked (via update_curr()) we add support to throttle
group entities (and their corresponding cfs_rqs) in the case where this is no
run-time remaining.
Throttled entities are dequeued to prevent scheduling, additionally we mark
them as throttled (using cfs_rq->throttled) to prevent them from becoming
re-enqueued until they are unthrottled. A list of a task_group's throttled
entities are maintained on the cfs_bandwidth structure.
Note: While the machinery for throttling is added in this patch the act of
throttling an entity exceeding its bandwidth is deferred until later within
the series.
Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184757.480608533@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Since quota is managed using a global state but consumed on a per-cpu basis
we need to ensure that our per-cpu state is appropriately synchronized.
Most importantly, runtime that is state (from a previous period) should not be
locally consumable.
We take advantage of existing sched_clock synchronization about the jiffy to
efficiently detect whether we have (globally) crossed a quota boundary above.
One catch is that the direction of spread on sched_clock is undefined,
specifically, we don't know whether our local clock is behind or ahead
of the one responsible for the current expiration time.
Fortunately we can differentiate these by considering whether the
global deadline has advanced. If it has not, then we assume our clock to be
"fast" and advance our local expiration; otherwise, we know the deadline has
truly passed and we expire our local runtime.
Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184757.379275352@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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This patch adds a per-task_group timer which handles the refresh of the global
CFS bandwidth pool.
Since the RT pool is using a similar timer there's some small refactoring to
share this support.
Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184757.277271273@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Account bandwidth usage on the cfs_rq level versus the task_groups to which
they belong. Whether we are tracking bandwidth on a given cfs_rq is maintained
under cfs_rq->runtime_enabled.
cfs_rq's which belong to a bandwidth constrained task_group have their runtime
accounted via the update_curr() path, which withdraws bandwidth from the global
pool as desired. Updates involving the global pool are currently protected
under cfs_bandwidth->lock, local runtime is protected by rq->lock.
This patch only assigns and tracks quota, no action is taken in the case that
cfs_rq->runtime_used exceeds cfs_rq->runtime_assigned.
Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Nikhil Rao <ncrao@google.com>
Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184757.179386821@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Add constraints validation for CFS bandwidth hierarchies.
Validate that:
max(child bandwidth) <= parent_bandwidth
In a quota limited hierarchy, an unconstrained entity
(e.g. bandwidth==RUNTIME_INF) inherits the bandwidth of its parent.
This constraint is chosen over sum(child_bandwidth) as notion of over-commit is
valuable within SCHED_OTHER. Some basic code from the RT case is re-factored
for reuse.
Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184757.083774572@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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In this patch we introduce the notion of CFS bandwidth, partitioned into
globally unassigned bandwidth, and locally claimed bandwidth.
- The global bandwidth is per task_group, it represents a pool of unclaimed
bandwidth that cfs_rqs can allocate from.
- The local bandwidth is tracked per-cfs_rq, this represents allotments from
the global pool bandwidth assigned to a specific cpu.
Bandwidth is managed via cgroupfs, adding two new interfaces to the cpu subsystem:
- cpu.cfs_period_us : the bandwidth period in usecs
- cpu.cfs_quota_us : the cpu bandwidth (in usecs) that this tg will be allowed
to consume over period above.
Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Nikhil Rao <ncrao@google.com>
Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184756.972636699@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Introduce hierarchical task accounting for the group scheduling case in CFS, as
well as promoting the responsibility for maintaining rq->nr_running to the
scheduling classes.
The primary motivation for this is that with scheduling classes supporting
bandwidth throttling it is possible for entities participating in throttled
sub-trees to not have root visible changes in rq->nr_running across activate
and de-activate operations. This in turn leads to incorrect idle and
weight-per-task load balance decisions.
This also allows us to make a small fixlet to the fastpath in pick_next_task()
under group scheduling.
Note: this issue also exists with the existing sched_rt throttling mechanism.
This patch does not address that.
Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184756.878333391@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Setting child->prio = current->normal_prio _after_ SCHED_RESET_ON_FORK has
been handled for an RT parent gives birth to a deranged mutant child with
non-RT policy, but RT prio and sched_class.
Move PI leakage protection up, always set priorities and weight, and if the
child is leaving RT class, reset rt_priority to the proper value.
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1311779695.8691.2.camel@marge.simson.net
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Since commit a2d47777 ("sched: fix stale value in average load per task")
the variable rq->avg_load_per_task is no longer required. Remove it.
Signed-off-by: Jan H. Schönherr <schnhrr@cs.tu-berlin.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1312189408-17172-1-git-send-email-schnhrr@cs.tu-berlin.de
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial: (43 commits)
fs: Merge split strings
treewide: fix potentially dangerous trailing ';' in #defined values/expressions
uwb: Fix misspelling of neighbourhood in comment
net, netfilter: Remove redundant goto in ebt_ulog_packet
trivial: don't touch files that are removed in the staging tree
lib/vsprintf: replace link to Draft by final RFC number
doc: Kconfig: `to be' -> `be'
doc: Kconfig: Typo: square -> squared
doc: Konfig: Documentation/power/{pm => apm-acpi}.txt
drivers/net: static should be at beginning of declaration
drivers/media: static should be at beginning of declaration
drivers/i2c: static should be at beginning of declaration
XTENSA: static should be at beginning of declaration
SH: static should be at beginning of declaration
MIPS: static should be at beginning of declaration
ARM: static should be at beginning of declaration
rcu: treewide: Do not use rcu_read_lock_held when calling rcu_dereference_check
Update my e-mail address
PCIe ASPM: forcedly -> forcibly
gma500: push through device driver tree
...
Fix up trivial conflicts:
- arch/arm/mach-ep93xx/dma-m2p.c (deleted)
- drivers/gpio/gpio-ep93xx.c (renamed and context nearby)
- drivers/net/r8169.c (just context changes)
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Sync with Linus' tree to be able to apply pending patches that
are based on newer code already present upstream.
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Since ca5ecddf (rcu: define __rcu address space modifier for sparse)
rcu_dereference_check use rcu_read_lock_held as a part of condition
automatically so callers do not have to do that as well.
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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* 'kvm-updates/3.1' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (143 commits)
KVM: IOMMU: Disable device assignment without interrupt remapping
KVM: MMU: trace mmio page fault
KVM: MMU: mmio page fault support
KVM: MMU: reorganize struct kvm_shadow_walk_iterator
KVM: MMU: lockless walking shadow page table
KVM: MMU: do not need atomicly to set/clear spte
KVM: MMU: introduce the rules to modify shadow page table
KVM: MMU: abstract some functions to handle fault pfn
KVM: MMU: filter out the mmio pfn from the fault pfn
KVM: MMU: remove bypass_guest_pf
KVM: MMU: split kvm_mmu_free_page
KVM: MMU: count used shadow pages on prepareing path
KVM: MMU: rename 'pt_write' to 'emulate'
KVM: MMU: cleanup for FNAME(fetch)
KVM: MMU: optimize to handle dirty bit
KVM: MMU: cache mmio info on page fault path
KVM: x86: introduce vcpu_mmio_gva_to_gpa to cleanup the code
KVM: MMU: do not update slot bitmap if spte is nonpresent
KVM: MMU: fix walking shadow page table
KVM guest: KVM Steal time registration
...
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This patch makes update_rq_clock() aware of steal time.
The mechanism of operation is not different from irq_time,
and follows the same principles. This lives in a CONFIG
option itself, and can be compiled out independently of
the rest of steal time reporting. The effect of disabling it
is that the scheduler will still report steal time (that cannot be
disabled), but won't use this information for cpu power adjustments.
Everytime update_rq_clock_task() is invoked, we query information
about how much time was stolen since last call, and feed it into
sched_rt_avg_update().
Although steal time reporting in account_process_tick() keeps
track of the last time we read the steal clock, in prev_steal_time,
this patch do it independently using another field,
prev_steal_time_rq. This is because otherwise, information about time
accounted in update_process_tick() would never reach us in update_rq_clock().
Signed-off-by: Glauber Costa <glommer@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Tested-by: Eric B Munson <emunson@mgebm.net>
CC: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
CC: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
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This patch accounts steal time time in account_process_tick.
If one or more tick is considered stolen in the current
accounting cycle, user/system accounting is skipped. Idle is fine,
since the hypervisor does not report steal time if the guest
is halted.
Accounting steal time from the core scheduler give us the
advantage of direct acess to the runqueue data. In a later
opportunity, it can be used to tweak cpu power and make
the scheduler aware of the time it lost.
[avi: <asm/paravirt.h> doesn't exist on many archs]
Signed-off-by: Glauber Costa <glommer@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Tested-by: Eric B Munson <emunson@mgebm.net>
CC: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
CC: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (24 commits)
sched: Cleanup duplicate local variable in [enqueue|dequeue]_task_fair
sched: Replace use of entity_key()
sched: Separate group-scheduling code more clearly
sched: Reorder root_domain to remove 64 bit alignment padding
sched: Do not attempt to destroy uninitialized rt_bandwidth
sched: Remove unused function cpu_cfs_rq()
sched: Fix (harmless) typo 'CONFG_FAIR_GROUP_SCHED'
sched, cgroup: Optimize load_balance_fair()
sched: Don't update shares twice on on_rq parent
sched: update correct entity's runtime in check_preempt_wakeup()
xtensa: Use generic config PREEMPT definition
h8300: Use generic config PREEMPT definition
m32r: Use generic PREEMPT config
sched: Skip autogroup when looking for all rt sched groups
sched: Simplify mutex_spin_on_owner()
sched: Remove rcu_read_lock() from wake_affine()
sched: Generalize sleep inside spinlock detection
sched: Make sleeping inside spinlock detection working in !CONFIG_PREEMPT
sched: Isolate preempt counting in its own config option
sched: Remove pointless in_atomic() definition check
...
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Clean up cfs/rt runqueue initialization by moving group scheduling
related code into the corresponding functions.
Also, keep group scheduling as an add-on, so that things are only done
additionally, i. e. remove the init_*_rq() calls from init_tg_*_entry().
(This removes a redundant initalization during sched_init()).
In case of group scheduling rt_rq->highest_prio.curr is now initialized
twice, but adding another #ifdef seems not worth it.
Signed-off-by: Jan H. Schönherr <schnhrr@cs.tu-berlin.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1310661163-16606-1-git-send-email-schnhrr@cs.tu-berlin.de
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Reorder root_domain to remove 8 bytes of alignment padding on 64 bit
builds, this shrinks the size from 1736 to 1728 bytes, therefore using
one fewer cachelines.
Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1310726492.1977.5.camel@castor.rsk
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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If a task group is to be created and alloc_fair_sched_group() fails,
then the rt_bandwidth of the corresponding task group is not yet
initialized. The caller, sched_create_group(), starts a clean up
procedure which calls free_rt_sched_group() which unconditionally
destroys the not yet initialized rt_bandwidth.
This crashes or hangs the system in lock_hrtimer_base(): UP systems
dereference a NULL pointer, while SMP systems loop endlessly on a
condition that cannot become true.
This patch simply avoids the destruction of rt_bandwidth when the
initialization code path was not reached.
(This was discovered by accident with a custom kernel modification.)
Signed-off-by: Bianca Lutz <sowilo@cs.tu-berlin.de>
Signed-off-by: Jan Schoenherr <schnhrr@cs.tu-berlin.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1310580816-10861-7-git-send-email-schnhrr@cs.tu-berlin.de
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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This patch fixes a typo located in a comment.
Signed-off-by: Jan Schoenherr <schnhrr@cs.tu-berlin.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1310580816-10861-2-git-send-email-schnhrr@cs.tu-berlin.de
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Use for_each_leaf_cfs_rq() instead of list_for_each_entry_rcu(), this
achieves that load_balance_fair() only iterates those task_groups that
actually have tasks on busiest, and that we iterate bottom-up, trying to
move light groups before the heavier ones.
No idea if it will actually work out to be beneficial in practice, does
anybody have a cgroup workload that might show a difference one way or
the other?
[ Also move update_h_load to sched_fair.c, loosing #ifdef-ery ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/1310557009.2586.28.camel@twins
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Merge reason: pick up the latest scheduler fixes.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing into sched/core
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The sleeping inside spinlock detection is actually used
for more general sleeping inside atomic sections
debugging: preemption disabled, rcu read side critical
sections, interrupts, interrupt disabled, etc...
Change the name of the config and its help section to
reflect its more general role.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
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Create a new CONFIG_PREEMPT_COUNT that handles the inc/dec
of preempt count offset independently. So that the offset
can be updated by preempt_disable() and preempt_enable()
even without the need for CONFIG_PREEMPT beeing set.
This prepares to make CONFIG_DEBUG_SPINLOCK_SLEEP working
with !CONFIG_PREEMPT where it currently doesn't detect
code that sleeps inside explicit preemption disabled
sections.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
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It's really supposed to be defined here. If it's not then
we actually want the build to crash so that we know it,
and not keep it silent.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
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It does not make sense to rcu_read_lock/unlock() in every loop
iteration while spinning on the mutex.
Move the rcu protection outside the loop. Also simplify the
return path to always check for lock->owner == NULL which
meets the requirements of both owner changed and need_resched()
caused loop exits.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1106101458350.11814@ionos
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Merge reason: Move to a (much) newer base.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace into sched/urgent
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The unlikely() used in ttwu_post_activation() tests if the rq->idle_stamp
is set. But since this is for a wakeup, and wakeups happen when tasks
block on IO, and blocking tasks on IO may put the system into idle,
this can actually be a common occurence.
Running the annotated branch profiler on an average desktop running
firefox, evolution, xchat and distcc, the report shows:
correct incorrect % Function File Line
------- --------- - -------- ---- ----
34884862 146110926 80 ttwu_post_activation sched.c 2309
80% of the time, this unlikely is incorrect. Best not to assume what the
result is, and just remove the branch annotation.
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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