Commit Graph

1389 Commits

Author SHA1 Message Date
Ingo Molnar
050c6c9b89 sched: Remove debugging check
Linus reported that the new warning introduced by commit f26f9aff6a
"Sched: fix skip_clock_update optimization" triggers. The need_resched
flag can be set by other CPUs asynchronously so this debug check is
bogus - remove it.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <AANLkTinJ8hAG1TpyC+CSYPR47p48+1=E7fiC45hMXT_1@mail.gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-12-19 23:24:27 +01:00
Peter Zijlstra
8e92c20183 sched: Fix the irqtime code for 32bit
Since the irqtime accounting is using non-atomic u64 and can be read
from remote cpus (writes are strictly cpu local, reads are not) we
have to deal with observing partial updates.

When we do observe partial updates the clock movement (in particular,
->clock_task movement) will go funny (in either direction), a
subsequent clock update (observing the full update) will make it go
funny in the oposite direction.

Since we rely on these clocks to be strictly monotonic we cannot
suffer backwards motion. One possible solution would be to simply
ignore all backwards deltas, but that will lead to accounting
artefacts, most notable: clock_task + irq_time != clock, this
inaccuracy would end up in user visible stats.

Therefore serialize the reads using a seqcount.

Reviewed-by: Venkatesh Pallipadi <venki@google.com>
Reported-by: Mikael Pettersson <mikpe@it.uu.se>
Tested-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1292242434.6803.200.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-12-16 11:17:47 +01:00
Peter Zijlstra
fe44d62122 sched: Fix the irqtime code to deal with u64 wraps
Some ARM systems have a short sched_clock() [ which needs to be fixed
too ], but this exposed a bug in the irq_time code as well, it doesn't
deal with wraps at all.

Fix the irq_time code to deal with u64 wraps by re-writing the code to
only use delta increments, which avoids the whole issue.

Reviewed-by: Venkatesh Pallipadi <venki@google.com>
Reported-by: Mikael Pettersson <mikpe@it.uu.se>
Tested-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1292242433.6803.199.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-12-16 11:17:46 +01:00
Mike Galbraith
f26f9aff6a Sched: fix skip_clock_update optimization
idle_balance() drops/retakes rq->lock, leaving the previous task
vulnerable to set_tsk_need_resched().  Clear it after we return
from balancing instead, and in setup_thread_stack() as well, so
no successfully descheduled or never scheduled task has it set.

Need resched confused the skip_clock_update logic, which assumes
that the next call to update_rq_clock() will come nearly immediately
after being set.  Make the optimization robust against the waking
a sleeper before it sucessfully deschedules case by checking that
the current task has not been dequeued before setting the flag,
since it is that useless clock update we're trying to save, and
clear unconditionally in schedule() proper instead of conditionally
in put_prev_task().

Signed-off-by: Mike Galbraith <efault@gmx.de>
Reported-by: Bjoern B. Brandenburg <bbb.lst@gmail.com>
Tested-by: Yong Zhang <yong.zhang0@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: stable@kernel.org
LKML-Reference: <1291802742.1417.9.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-12-08 20:15:06 +01:00
Peter Zijlstra
0f004f5a69 sched: Cure more NO_HZ load average woes
There's a long-running regression that proved difficult to fix and
which is hitting certain people and is rather annoying in its effects.

Damien reported that after 74f5187ac8 (sched: Cure load average vs
NO_HZ woes) his load average is unnaturally high, he also noted that
even with that patch reverted the load avgerage numbers are not
correct.

The problem is that the previous patch only solved half the NO_HZ
problem, it addressed the part of going into NO_HZ mode, not of
comming out of NO_HZ mode. This patch implements that missing half.

When comming out of NO_HZ mode there are two important things to take
care of:

 - Folding the pending idle delta into the global active count.
 - Correctly aging the averages for the idle-duration.

So with this patch the NO_HZ interaction should be complete and
behaviour between CONFIG_NO_HZ=[yn] should be equivalent.

Furthermore, this patch slightly changes the load average computation
by adding a rounding term to the fixed point multiplication.

Reported-by: Damien Wyart <damien.wyart@free.fr>
Reported-by: Tim McGrath <tmhikaru@gmail.com>
Tested-by: Damien Wyart <damien.wyart@free.fr>
Tested-by: Orion Poplawski <orion@cora.nwra.com>
Tested-by: Kyle McMartin <kyle@mcmartin.ca>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: stable@kernel.org
Cc: Chase Douglas <chase.douglas@canonical.com>
LKML-Reference: <1291129145.32004.874.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-12-08 20:15:04 +01:00
Peter Zijlstra
1e5a74059f sched: Fix cross-sched-class wakeup preemption
Instead of dealing with sched classes inside each check_preempt_curr()
implementation, pull out this logic into the generic wakeup preemption
path.

This fixes a hang in KVM (and others) where we are waiting for the
stop machine thread to run ...

Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Tested-by: Marcelo Tosatti <mtosatti@redhat.com>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1288891946.2039.31.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-11-11 14:37:23 +01:00
Suresh Siddha
aae6d3ddd8 sched: Use group weight, idle cpu metrics to fix imbalances during idle
Currently we consider a sched domain to be well balanced when the imbalance
is less than the domain's imablance_pct. As the number of cores and threads
are increasing, current values of imbalance_pct (for example 25% for a
NUMA domain) are not enough to detect imbalances like:

a) On a WSM-EP system (two sockets, each having 6 cores and 12 logical threads),
24 cpu-hogging tasks get scheduled as 13 on one socket and 11 on another
socket. Leading to an idle HT cpu.

b) On a hypothetial 2 socket NHM-EX system (each socket having 8 cores and
16 logical threads), 16 cpu-hogging tasks can get scheduled as 9 on one
socket and 7 on another socket. Leaving one core in a socket idle
whereas in another socket we have a core having both its HT siblings busy.

While this issue can be fixed by decreasing the domain's imbalance_pct
(by making it a function of number of logical cpus in the domain), it
can potentially cause more task migrations across sched groups in an
overloaded case.

Fix this by using imbalance_pct only during newly_idle and busy
load balancing. And during idle load balancing, check if there
is an imbalance in number of idle cpu's across the busiest and this
sched_group or if the busiest group has more tasks than its weight that
the idle cpu in this_group can pull.

Reported-by: Nikhil Rao <ncrao@google.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1284760952.2676.11.camel@sbsiddha-MOBL3.sc.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-11-10 23:13:56 +01:00
Linus Torvalds
37542b6a7e Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched_stat: Update sched_info_queue/dequeue() code comments
  sched, cgroup: Fixup broken cgroup movement
2010-10-29 08:05:33 -07:00
Peter Zijlstra
b2b5ce022a sched, cgroup: Fixup broken cgroup movement
Dima noticed that we fail to correct the ->vruntime of sleeping tasks
when we move them between cgroups.

Reported-by: Dima Zavin <dima@android.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Mike Galbraith <efault@gmx.de>
LKML-Reference: <1287150604.29097.1513.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-10-22 14:16:45 +02:00
Linus Torvalds
bc4016f481 Merge branch 'sched-core-for-linus' of 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: (29 commits)
  sched: Export account_system_vtime()
  sched: Call tick_check_idle before __irq_enter
  sched: Remove irq time from available CPU power
  sched: Do not account irq time to current task
  x86: Add IRQ_TIME_ACCOUNTING
  sched: Add IRQ_TIME_ACCOUNTING, finer accounting of irq time
  sched: Add a PF flag for ksoftirqd identification
  sched: Consolidate account_system_vtime extern declaration
  sched: Fix softirq time accounting
  sched: Drop group_capacity to 1 only if local group has extra capacity
  sched: Force balancing on newidle balance if local group has capacity
  sched: Set group_imb only a task can be pulled from the busiest cpu
  sched: Do not consider SCHED_IDLE tasks to be cache hot
  sched: Drop all load weight manipulation for RT tasks
  sched: Create special class for stop/migrate work
  sched: Unindent labels
  sched: Comment updates: fix default latency and granularity numbers
  tracing/sched: Add sched_pi_setprio tracepoint
  sched: Give CPU bound RT tasks preference
  sched: Try not to migrate higher priority RT tasks
  ...
2010-10-21 12:55:43 -07:00
Linus Torvalds
5d70f79b5e Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (163 commits)
  tracing: Fix compile issue for trace_sched_wakeup.c
  [S390] hardirq: remove pointless header file includes
  [IA64] Move local_softirq_pending() definition
  perf, powerpc: Fix power_pmu_event_init to not use event->ctx
  ftrace: Remove recursion between recordmcount and scripts/mod/empty
  jump_label: Add COND_STMT(), reducer wrappery
  perf: Optimize sw events
  perf: Use jump_labels to optimize the scheduler hooks
  jump_label: Add atomic_t interface
  jump_label: Use more consistent naming
  perf, hw_breakpoint: Fix crash in hw_breakpoint creation
  perf: Find task before event alloc
  perf: Fix task refcount bugs
  perf: Fix group moving
  irq_work: Add generic hardirq context callbacks
  perf_events: Fix transaction recovery in group_sched_in()
  perf_events: Fix bogus AMD64 generic TLB events
  perf_events: Fix bogus context time tracking
  tracing: Remove parent recording in latency tracer graph options
  tracing: Use one prologue for the preempt irqs off tracer function tracers
  ...
2010-10-21 12:54:49 -07:00
Linus Torvalds
888a6f77e0 Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (52 commits)
  sched: fix RCU lockdep splat from task_group()
  rcu: using ACCESS_ONCE() to observe the jiffies_stall/rnp->qsmask value
  sched: suppress RCU lockdep splat in task_fork_fair
  net: suppress RCU lockdep false positive in sock_update_classid
  rcu: move check from rcu_dereference_bh to rcu_read_lock_bh_held
  rcu: Add advice to PROVE_RCU_REPEATEDLY kernel config parameter
  rcu: Add tracing data to support queueing models
  rcu: fix sparse errors in rcutorture.c
  rcu: only one evaluation of arg in rcu_dereference_check() unless sparse
  kernel: Remove undead ifdef CONFIG_DEBUG_LOCK_ALLOC
  rcu: fix _oddness handling of verbose stall warnings
  rcu: performance fixes to TINY_PREEMPT_RCU callback checking
  rcu: upgrade stallwarn.txt documentation for CPU-bound RT processes
  vhost: add __rcu annotations
  rcu: add comment stating that list_empty() applies to RCU-protected lists
  rcu: apply TINY_PREEMPT_RCU read-side speedup to TREE_PREEMPT_RCU
  rcu: combine duplicate code, courtesy of CONFIG_PREEMPT_RCU
  rcu: Upgrade srcu_read_lock() docbook about SRCU grace periods
  rcu: document ways of stalling updates in low-memory situations
  rcu: repair code-duplication FIXMEs
  ...
2010-10-21 12:54:12 -07:00
KOSAKI Motohiro
b0ae198113 security: remove unused parameter from security_task_setscheduler()
All security modules shouldn't change sched_param parameter of
security_task_setscheduler().  This is not only meaningless, but also
make a harmful result if caller pass a static variable.

This patch remove policy and sched_param parameter from
security_task_setscheduler() becuase none of security module is
using it.

Cc: James Morris <jmorris@namei.org>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: James Morris <jmorris@namei.org>
2010-10-21 10:12:44 +11:00
Ingo Molnar
b7dadc3879 sched: Export account_system_vtime()
KVM uses it for example:

 ERROR: "account_system_vtime" [arch/x86/kvm/kvm.ko] undefined!

Cc: Venkatesh Pallipadi <venki@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1286237003-12406-3-git-send-email-venki@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-10-18 20:52:30 +02:00
Venkatesh Pallipadi
d267f87fb8 sched: Call tick_check_idle before __irq_enter
When CPU is idle and on first interrupt, irq_enter calls tick_check_idle()
to notify interruption from idle. But, there is a problem if this call
is done after __irq_enter, as all routines in __irq_enter may find
stale time due to yet to be done tick_check_idle.

Specifically, trace calls in __irq_enter when they use global clock and also
account_system_vtime change in this patch as it wants to use sched_clock_cpu()
to do proper irq timing.

But, tick_check_idle was moved after __irq_enter intentionally to
prevent problem of unneeded ksoftirqd wakeups by the commit ee5f80a:

    irq: call __irq_enter() before calling the tick_idle_check
    Impact: avoid spurious ksoftirqd wakeups

Moving tick_check_idle() before __irq_enter and wrapping it with
local_bh_enable/disable would solve both the problems.

Fixed-by: Yong Zhang <yong.zhang0@gmail.com>
Signed-off-by: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1286237003-12406-9-git-send-email-venki@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-10-18 20:52:29 +02:00
Venkatesh Pallipadi
aa48380851 sched: Remove irq time from available CPU power
The idea was suggested by Peter Zijlstra here:

  http://marc.info/?l=linux-kernel&m=127476934517534&w=2

irq time is technically not available to the tasks running on the CPU.
This patch removes irq time from CPU power piggybacking on
sched_rt_avg_update().

Tested this by keeping CPU X busy with a network intensive task having 75%
oa a single CPU irq processing (hard+soft) on a 4-way system. And start seven
cycle soakers on the system. Without this change, there will be two tasks on
each CPU. With this change, there is a single task on irq busy CPU X and
remaining 7 tasks are spread around among other 3 CPUs.

Signed-off-by: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1286237003-12406-8-git-send-email-venki@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-10-18 20:52:27 +02:00
Venkatesh Pallipadi
305e6835e0 sched: Do not account irq time to current task
Scheduler accounts both softirq and interrupt processing times to the
currently running task. This means, if the interrupt processing was
for some other task in the system, then the current task ends up being
penalized as it gets shorter runtime than otherwise.

Change sched task accounting to acoount only actual task time from
currently running task. Now update_curr(), modifies the delta_exec to
depend on rq->clock_task.

Note that this change only handles CONFIG_IRQ_TIME_ACCOUNTING case. We can
extend this to CONFIG_VIRT_CPU_ACCOUNTING with minimal effort. But, thats
for later.

This change will impact scheduling behavior in interrupt heavy conditions.

Tested on a 4-way system with eth0 handled by CPU 2 and a network heavy
task (nc) running on CPU 3 (and no RSS/RFS). With that I have CPU 2
spending 75%+ of its time in irq processing. CPU 3 spending around 35%
time running nc task.

Now, if I run another CPU intensive task on CPU 2, without this change
/proc/<pid>/schedstat shows 100% of time accounted to this task. With this
change, it rightly shows less than 25% accounted to this task as remaining
time is actually spent on irq processing.

Signed-off-by: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1286237003-12406-7-git-send-email-venki@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-10-18 20:52:26 +02:00
Venkatesh Pallipadi
b52bfee445 sched: Add IRQ_TIME_ACCOUNTING, finer accounting of irq time
s390/powerpc/ia64 have support for CONFIG_VIRT_CPU_ACCOUNTING which does
the fine granularity accounting of user, system, hardirq, softirq times.
Adding that option on archs like x86 will be challenging however, given the
state of TSC reliability on various platforms and also the overhead it will
add in syscall entry exit.

Instead, add a lighter variant that only does finer accounting of
hardirq and softirq times, providing precise irq times (instead of timer tick
based samples). This accounting is added with a new config option
CONFIG_IRQ_TIME_ACCOUNTING so that there won't be any overhead for users not
interested in paying the perf penalty.

This accounting is based on sched_clock, with the code being generic.
So, other archs may find it useful as well.

This patch just adds the core logic and does not enable this logic yet.

Signed-off-by: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1286237003-12406-5-git-send-email-venki@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-10-18 20:52:24 +02:00
Venkatesh Pallipadi
75e1056f5c sched: Fix softirq time accounting
Peter Zijlstra found a bug in the way softirq time is accounted in
VIRT_CPU_ACCOUNTING on this thread:

   http://lkml.indiana.edu/hypermail//linux/kernel/1009.2/01366.html

The problem is, softirq processing uses local_bh_disable internally. There
is no way, later in the flow, to differentiate between whether softirq is
being processed or is it just that bh has been disabled. So, a hardirq when bh
is disabled results in time being wrongly accounted as softirq.

Looking at the code a bit more, the problem exists in !VIRT_CPU_ACCOUNTING
as well. As account_system_time() in normal tick based accouting also uses
softirq_count, which will be set even when not in softirq with bh disabled.

Peter also suggested solution of using 2*SOFTIRQ_OFFSET as irq count
for local_bh_{disable,enable} and using just SOFTIRQ_OFFSET while softirq
processing. The patch below does that and adds API in_serving_softirq() which
returns whether we are currently processing softirq or not.

Also changes one of the usages of softirq_count in net/sched/cls_cgroup.c
to in_serving_softirq.

Looks like many usages of in_softirq really want in_serving_softirq. Those
changes can be made individually on a case by case basis.

Signed-off-by: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1286237003-12406-2-git-send-email-venki@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-10-18 20:52:20 +02:00
Nikhil Rao
ef8002f684 sched: Do not consider SCHED_IDLE tasks to be cache hot
This patch adds a check in task_hot to return if the task has SCHED_IDLE
policy. SCHED_IDLE tasks have very low weight, and when run with regular
workloads, are typically scheduled many milliseconds apart. There is no
need to consider these tasks hot for load balancing.

Signed-off-by: Nikhil Rao <ncrao@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1287173550-30365-2-git-send-email-ncrao@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-10-18 20:52:15 +02:00
Linus Walleij
17bdcf949d sched: Drop all load weight manipulation for RT tasks
Load weights are for the CFS, they do not belong in the RT task. This makes all
RT scheduling classes leave the CFS weights alone.

This fixes a real bug as well: I noticed the following phonomena: a process
elevated to SCHED_RR forks with SCHED_RESET_ON_FORK set, and the child is
indeed SCHED_OTHER, and the niceval is indeed reset to 0. However the weight
inserted by set_load_weight() remains at 0, giving the task insignificat
priority.

With this fix, the weight is reset to what the task had before being elevated
to SCHED_RR/SCHED_FIFO.

Cc: Lennart Poettering <lennart@poettering.net>
Cc: stable@kernel.org
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1286807811-10568-1-git-send-email-linus.walleij@stericsson.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-10-18 18:41:59 +02:00
Peter Zijlstra
34f971f6f7 sched: Create special class for stop/migrate work
In order to separate the stop/migrate work thread from the SCHED_FIFO
implementation, create a special class for it that is of higher priority than
SCHED_FIFO itself.

This currently solves a problem where cpu-hotplug consumes so much cpu-time
that the SCHED_FIFO class gets throttled, but has the bandwidth replenishment
timer pending on the now dead cpu.

It is also required for when we add the planned deadline scheduling class above
SCHED_FIFO, as the stop/migrate thread still needs to transcent those tasks.

Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1285165776.2275.1022.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-10-18 18:41:58 +02:00
Peter Zijlstra
4924627423 sched: Unindent labels
Labels should be on column 0.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-10-18 18:41:56 +02:00
Ingo Molnar
ed859ed3b0 Merge branch 'linus' into sched/core
Merge reason: update from -rc5 to -almost-final

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-10-14 09:11:46 +02:00
Peter Zijlstra
6506cf6ce6 sched: fix RCU lockdep splat from task_group()
This addresses the following RCU lockdep splat:

[0.051203] CPU0: AMD QEMU Virtual CPU version 0.12.4 stepping 03
[0.052999] lockdep: fixing up alternatives.
[0.054105]
[0.054106] ===================================================
[0.054999] [ INFO: suspicious rcu_dereference_check() usage. ]
[0.054999] ---------------------------------------------------
[0.054999] kernel/sched.c:616 invoked rcu_dereference_check() without protection!
[0.054999]
[0.054999] other info that might help us debug this:
[0.054999]
[0.054999]
[0.054999] rcu_scheduler_active = 1, debug_locks = 1
[0.054999] 3 locks held by swapper/1:
[0.054999]  #0:  (cpu_add_remove_lock){+.+.+.}, at: [<ffffffff814be933>] cpu_up+0x42/0x6a
[0.054999]  #1:  (cpu_hotplug.lock){+.+.+.}, at: [<ffffffff810400d8>] cpu_hotplug_begin+0x2a/0x51
[0.054999]  #2:  (&rq->lock){-.-...}, at: [<ffffffff814be2f7>] init_idle+0x2f/0x113
[0.054999]
[0.054999] stack backtrace:
[0.054999] Pid: 1, comm: swapper Not tainted 2.6.35 #1
[0.054999] Call Trace:
[0.054999]  [<ffffffff81068054>] lockdep_rcu_dereference+0x9b/0xa3
[0.054999]  [<ffffffff810325c3>] task_group+0x7b/0x8a
[0.054999]  [<ffffffff810325e5>] set_task_rq+0x13/0x40
[0.054999]  [<ffffffff814be39a>] init_idle+0xd2/0x113
[0.054999]  [<ffffffff814be78a>] fork_idle+0xb8/0xc7
[0.054999]  [<ffffffff81068717>] ? mark_held_locks+0x4d/0x6b
[0.054999]  [<ffffffff814bcebd>] do_fork_idle+0x17/0x2b
[0.054999]  [<ffffffff814bc89b>] native_cpu_up+0x1c1/0x724
[0.054999]  [<ffffffff814bcea6>] ? do_fork_idle+0x0/0x2b
[0.054999]  [<ffffffff814be876>] _cpu_up+0xac/0x127
[0.054999]  [<ffffffff814be946>] cpu_up+0x55/0x6a
[0.054999]  [<ffffffff81ab562a>] kernel_init+0xe1/0x1ff
[0.054999]  [<ffffffff81003854>] kernel_thread_helper+0x4/0x10
[0.054999]  [<ffffffff814c353c>] ? restore_args+0x0/0x30
[0.054999]  [<ffffffff81ab5549>] ? kernel_init+0x0/0x1ff
[0.054999]  [<ffffffff81003850>] ? kernel_thread_helper+0x0/0x10
[0.056074] Booting Node   0, Processors  #1lockdep: fixing up alternatives.
[0.130045]  #2lockdep: fixing up alternatives.
[0.203089]  #3 Ok.
[0.275286] Brought up 4 CPUs
[0.276005] Total of 4 processors activated (16017.17 BogoMIPS).

The cgroup_subsys_state structures referenced by idle tasks are never
freed, because the idle tasks should be part of the root cgroup,
which is not removable.

The problem is that while we do in-fact hold rq->lock, the newly spawned
idle thread's cpu is not yet set to the correct cpu so the lockdep check
in task_group():

  lockdep_is_held(&task_rq(p)->lock)

will fail.

But this is a chicken and egg problem.  Setting the CPU's runqueue requires
that the CPU's runqueue already be set.  ;-)

So insert an RCU read-side critical section to avoid the complaint.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2010-10-07 10:41:07 -07:00
Ingo Molnar
90edf27fb8 Merge branch 'linus' into perf/core
Conflicts:
	kernel/hw_breakpoint.c

Merge reason: resolve the conflict.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-09-22 18:45:01 +02:00
Steven Rostedt
a8027073eb tracing/sched: Add sched_pi_setprio tracepoint
Add a tracepoint that shows the priority of a task being boosted
via priority inheritance.

Cc: Gregory Haskins <ghaskins@novell.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-09-21 10:56:41 -04:00
Ingo Molnar
cf84fd9632 Merge commit 'v2.6.36-rc5' into sched/core
Merge reason: Pick up the latest fixes in -rc5.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-09-21 13:56:49 +02:00
Peter Zijlstra
e9d2b06414 perf: Undo the per cpu-context timer stuff
Revert the timer per cpu-context timers because of unfortunate
nohz interaction. Fixing that would have been somewhat ugly, so
go back to driving things from the regular tick. Provide a
jiffies interval feature for people who want slower rotations.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <20100917093009.519845633@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-09-17 12:48:48 +02:00
Heiko Carstens
31915ab4cb sched: Remove branch hints within context_switch()
With 710390d9 "sched: Optimize branch hint in context_switch()"
the branch hint logic within context_switch() got inversed.

In fact the hints "if (likely(!mm))" and "if (likely(!prev->mm))"
mean that it is likely that the previous and next task are kernel
threads.

That assumption is certainly counter intuitive, but Tim has shown
that at least with his workload this is true. Nevertheless the
truth is: it depends on the current workload. So just remove the
annotations which also improves readability.

Reported-by: Tim Blechmann <tim@klingt.org>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <20100916124225.GA2209@osiris.boeblingen.de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-09-16 16:38:34 +02:00
Stanislaw Gruszka
e75e863dd5 sched: Fix user time incorrectly accounted as system time on 32-bit
We have 32-bit variable overflow possibility when multiply in
task_times() and thread_group_times() functions. When the
overflow happens then the scaled utime value becomes erroneously
small and the scaled stime becomes i erroneously big.

Reported here:

 https://bugzilla.redhat.com/show_bug.cgi?id=633037
 https://bugzilla.kernel.org/show_bug.cgi?id=16559

Reported-by: Michael Chapman <redhat-bugzilla@very.puzzling.org>
Reported-by: Ciriaco Garcia de Celis <sysman@etherpilot.com>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: <stable@kernel.org>  # 2.6.32.19+ (partially) and 2.6.33+
LKML-Reference: <20100914143513.GB8415@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-09-15 10:41:36 +02:00
Ingo Molnar
3aabae7d9d Merge branch 'tip/perf/core' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace into perf/core 2010-09-15 10:27:31 +02:00
Mathieu Desnoyers
7740191cd9 sched: Fix string comparison in /proc/sched_features
Fix incorrect handling of the following case:

 INTERACTIVE
 INTERACTIVE_SOMETHING_ELSE

The comparison only checks up to each element's length.

Changelog since v1:
 - Embellish using some Rostedtisms.
  [ mingo:                 ^^ == smaller and cleaner ]

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: <stable@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tony Lindgren <tony@atomide.com>
LKML-Reference: <20100913214700.GB16118@Krystal>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-09-14 13:23:45 +02:00
Peter Zijlstra
b5ab4cd563 perf: Per cpu-context rotation timer
Give each cpu-context its own timer so that it is a self contained
entity, this eases the way for per-pmu-per-cpu contexts as well as
provides the basic infrastructure to allow different rotation
times per pmu.

Things to look at:
 - folding the tick and these TICK_NSEC timers
 - separate task context rotation

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: paulus <paulus@samba.org>
Cc: stephane eranian <eranian@googlemail.com>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Lin Ming <ming.m.lin@intel.com>
Cc: Yanmin <yanmin_zhang@linux.intel.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-09-09 20:46:32 +02:00
Heiko Carstens
01a08546af sched: Add book scheduling domain
On top of the SMT and MC scheduling domains this adds the BOOK scheduling
domain. This is useful for NUMA like machines which do not have an interface
which tells which piece of memory is attached to which node or where the
hardware performs striping.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100831082844.253053798@de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-09-09 20:41:20 +02:00
Heiko Carstens
f269893c57 sched: Merge cpu_to_core_group functions
Merge and simplify the two cpu_to_core_group variants so that the
resulting function follows the same pattern like cpu_to_phys_group.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100831082843.953617555@de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-09-09 20:41:18 +02:00
Suresh Siddha
da2b71edd8 sched: Move sched_avg_update() to update_cpu_load()
Currently sched_avg_update() (which updates rt_avg stats in the rq)
is getting called from scale_rt_power() (in the load balance context)
which doesn't take rq->lock.

Fix it by moving the sched_avg_update() to more appropriate
update_cpu_load() where the CFS load gets updated as well.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1282596171.2694.3.camel@sbsiddha-MOBL3>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-09-09 20:39:33 +02:00
Christian Dietrich
ed2d372c07 sched: Remove unnecessary #ifdef CONFIG_SMP
The CONFIG_SMP ifdef isn't necessary at this point, because it
is checked in an outer ifdef level already and has no effect
here.

Cleanup only, no functional effect.

Signed-off-by: Christian Dietrich <qy03fugy@stud.informatik.uni-erlangen.de>
Cc: vamos-dev@i4.informatik.uni-erlangen.de
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Tejun Heo <tj@kernel.org>
LKML-Reference: <7a3a39ef3f765a4473cb026b1f204059568a7098.1283782701.git.qy03fugy@stud.informatik.uni-erlangen.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-09-08 08:14:20 +02:00
Tim Chen
9d0f4dcc5c mutex: Improve the scalability of optimistic spinning
There is a scalability issue for current implementation of optimistic
mutex spin in the kernel.  It is found on a 8 node 64 core Nehalem-EX
system (HT mode).

The intention of the optimistic mutex spin is to busy wait and spin on a
mutex if the owner of the mutex is running, in the hope that the mutex
will be released soon and be acquired, without the thread trying to
acquire mutex going to sleep. However, when we have a large number of
threads, contending for the mutex, we could have the mutex grabbed by
other thread, and then another ……, and we will keep spinning, wasting cpu
cycles and adding to the contention.  One possible fix is to quit
spinning and put the current thread on wait-list if mutex lock switch to
a new owner while we spin, indicating heavy contention (see the patch
included).

I did some testing on a 8 socket Nehalem-EX system with a total of 64
cores. Using Ingo's test-mutex program that creates/delete files with 256
threads (http://lkml.org/lkml/2006/1/8/50) , I see the following speed up
after putting in the mutex spin fix:

 ./mutex-test V 256 10
                 Ops/sec
 2.6.34          62864
 With fix        197200

Repeating the test with Aim7 fserver workload, again there is a speed up
with the fix:

                 Jobs/min
 2.6.34          91657
 With fix        149325

To look at the impact on the distribution of mutex acquisition time, I
collected the mutex acquisition time on Aim7 fserver workload with some
instrumentation.  The average acquisition time is reduced by 48% and
number of contentions reduced by 32%.

                 #contentions    Time to acquire mutex (cycles)
 2.6.34          72973           44765791
 With fix        49210           23067129

The histogram of mutex acquisition time is listed below.  The acquisition
time is in 2^bin cycles.  We see that without the fix, the acquisition
time is mostly around 2^26 cycles.  With the fix, we the distribution get
spread out a lot more towards the lower cycles, starting from 2^13.
However, there is an increase of the tail distribution with the fix at
2^28 and 2^29 cycles.  It seems a small price to pay for the reduced
average acquisition time and also getting the cpu to do useful work.

 Mutex acquisition time distribution (acq time = 2^bin cycles):
         2.6.34                  With Fix
 bin     #occurrence     %       #occurrence     %
 11      2               0.00%   120             0.24%
 12      10              0.01%   790             1.61%
 13      14              0.02%   2058            4.18%
 14      86              0.12%   3378            6.86%
 15      393             0.54%   4831            9.82%
 16      710             0.97%   4893            9.94%
 17      815             1.12%   4667            9.48%
 18      790             1.08%   5147            10.46%
 19      580             0.80%   6250            12.70%
 20      429             0.59%   6870            13.96%
 21      311             0.43%   1809            3.68%
 22      255             0.35%   2305            4.68%
 23      317             0.44%   916             1.86%
 24      610             0.84%   233             0.47%
 25      3128            4.29%   95              0.19%
 26      63902           87.69%  122             0.25%
 27      619             0.85%   286             0.58%
 28      0               0.00%   3536            7.19%
 29      0               0.00%   903             1.83%
 30      0               0.00%   0               0.00%

I've done similar experiments with 2.6.35 kernel on smaller boxes as
well.  One is on a dual-socket Westmere box (12 cores total, with HT).
Another experiment is on an old dual-socket Core 2 box (4 cores total, no
HT)

On the 12-core Westmere box, I see a 250% increase for Ingo's mutex-test
program with my mutex patch but no significant difference in aim7's
fserver workload.

On the 4-core Core 2 box, I see the difference with the patch for both
mutex-test and aim7 fserver are negligible.

So far, it seems like the patch has not caused regression on smaller
systems.

Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: <stable@kernel.org> # .35.x
LKML-Reference: <1282168827.9542.72.camel@schen9-DESK>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-08-23 10:56:27 +02:00
Linus Torvalds
c4efd6b569 Merge branch 'sched-core-for-linus' of 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: (27 commits)
  sched: Use correct macro to display sched_child_runs_first in /proc/sched_debug
  sched: No need for bootmem special cases
  sched: Revert nohz_ratelimit() for now
  sched: Reduce update_group_power() calls
  sched: Update rq->clock for nohz balanced cpus
  sched: Fix spelling of sibling
  sched, cpuset: Drop __cpuexit from cpu hotplug callbacks
  sched: Fix the racy usage of thread_group_cputimer() in fastpath_timer_check()
  sched: run_posix_cpu_timers: Don't check ->exit_state, use lock_task_sighand()
  sched: thread_group_cputime: Simplify, document the "alive" check
  sched: Remove the obsolete exit_state/signal hacks
  sched: task_tick_rt: Remove the obsolete ->signal != NULL check
  sched: __sched_setscheduler: Read the RLIMIT_RTPRIO value lockless
  sched: Fix comments to make them DocBook happy
  sched: Fix fix_small_capacity
  powerpc: Exclude arch_sd_sibiling_asym_packing() on UP
  powerpc: Enable asymmetric SMT scheduling on POWER7
  sched: Add asymmetric group packing option for sibling domain
  sched: Fix capacity calculations for SMT4
  sched: Change nohz idle load balancing logic to push model
  ...
2010-08-06 09:39:22 -07:00
Ingo Molnar
0bcfe75807 Merge branch 'sched/urgent' into sched/core
Conflicts:
	include/linux/sched.h

Merge reason: Add the leftover .35 urgent bits, fix the conflict.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-08-05 09:46:29 +02:00
Ingo Molnar
dca45ad8af Merge branch 'linus' into sched/core
Merge reason: Move from the -rc3 to the almost-rc6 base.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-07-21 21:45:08 +02:00
Pekka Enberg
68c38fc3cb sched: No need for bootmem special cases
As of commit dcce284 ("mm: Extend gfp masking to the page
allocator") and commit 7e85ee0 ("slab,slub: don't enable
interrupts during early boot"), the slab allocator makes
sure we don't attempt to sleep during boot.

Therefore, remove bootmem special cases from the scheduler
and use plain GFP_KERNEL instead.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1279225102-2572-1-git-send-email-penberg@cs.helsinki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-07-17 12:06:22 +02:00
Peter Zijlstra
396e894d28 sched: Revert nohz_ratelimit() for now
Norbert reported that nohz_ratelimit() causes his laptop to burn about
4W (40%) extra. For now back out the change and see if we can adjust
the power management code to make better decisions.

Reported-by: Norbert Preining <preining@logic.at>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Mike Galbraith <efault@gmx.de>
Cc: Arjan van de Ven <arjan@infradead.org>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-07-17 12:05:44 +02:00
Ingo Molnar
08f8ba0799 Merge commit 'v2.6.35-rc4' into perf/core
Merge reason: Pick up the latest perf fixes

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-07-05 08:30:58 +02:00
Linus Torvalds
123f94f22e Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched: Cure nr_iowait_cpu() users
  init: Fix comment
  init, sched: Fix race between init and kthreadd
2010-07-02 09:52:58 -07:00
Peter Zijlstra
8c215bd389 sched: Cure nr_iowait_cpu() users
Commit 0224cf4c5e (sched: Intoduce get_cpu_iowait_time_us())
broke things by not making sure preemption was indeed disabled
by the callers of nr_iowait_cpu() which took the iowait value of
the current cpu.

This resulted in a heap of preempt warnings. Cure this by making
nr_iowait_cpu() take a cpu number and fix up the callers to pass
in the right number.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Maxim Levitsky <maximlevitsky@gmail.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: linux-pm@lists.linux-foundation.org
LKML-Reference: <1277968037.1868.120.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-07-01 09:39:48 +02:00
Thomas Gleixner
f384c954c9 Merge branch 'linus' into perf/core
Reason: Further changes conflict with upstream fixes

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2010-06-28 22:33:24 +02:00
Linus Torvalds
f014d937d6 Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched: Prevent compiler from optimising the sched_avg_update() loop
  sched: Fix over-scheduling bug
  sched: Fix PROVE_RCU vs cpu_cgroup
2010-06-28 12:18:30 -07:00
Will Deacon
0d98bb2656 sched: Prevent compiler from optimising the sched_avg_update() loop
GCC 4.4.1 on ARM has been observed to replace the while loop in
sched_avg_update with a call to uldivmod, resulting in the
following build failure at link-time:

kernel/built-in.o: In function `sched_avg_update':
 kernel/sched.c:1261: undefined reference to `__aeabi_uldivmod'
 kernel/sched.c:1261: undefined reference to `__aeabi_uldivmod'
make: *** [.tmp_vmlinux1] Error 1

This patch introduces a fake data hazard to the loop body to
prevent the compiler optimising the loop away.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-06-25 16:11:50 +02:00