linux.git/kernel/sched.c, branch v3.0-rc1

cpuset: Fix cpuset_cpus_allowed_fallback(), don't update tsk->rt.nr_cpus_allowed

2011-05-28T15:02:57+00:00

The rule is, we have to update tsk->rt.nr_cpus_allowed if we change
tsk->cpus_allowed. Otherwise RT scheduler may confuse.

Signed-off-by: KOSAKI Motohiro 
Cc: Oleg Nesterov 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/4DD4B3FA.5060901@jp.fujitsu.com
Signed-off-by: Ingo Molnar

sched: Fix ttwu() for __ARCH_WANT_INTERRUPTS_ON_CTXSW

2011-05-28T15:02:55+00:00

Marc reported that e4a52bcb9 (sched: Remove rq->lock from the first
half of ttwu()) broke his ARM-SMP machine. Now ARM is one of the few
__ARCH_WANT_INTERRUPTS_ON_CTXSW users, so that exception in the ttwu()
code was suspect.

Yong found that the interrupt could hit after context_switch() changes
current but before it clears p->on_cpu, if that interrupt were to
attempt a wake-up of p we would indeed find ourselves spinning in IRQ
context.

Fix this by reverting to the old behaviour for this situation and
perform a full remote wake-up.

Cc: Frank Rowand 
Cc: Yong Zhang 
Cc: Oleg Nesterov 
Reported-by: Marc Zyngier 
Tested-by: Marc Zyngier 
Signed-off-by: Peter Zijlstra 
Signed-off-by: Ingo Molnar

cgroups: add per-thread subsystem callbacks

2011-05-27T00:12:34+00:00

Add cgroup subsystem callbacks for per-thread attachment in atomic contexts

Add can_attach_task(), pre_attach(), and attach_task() as new callbacks
for cgroups's subsystem interface.  Unlike can_attach and attach, these
are for per-thread operations, to be called potentially many times when
attaching an entire threadgroup.

Also, the old "bool threadgroup" interface is removed, as replaced by
this.  All subsystems are modified for the new interface - of note is
cpuset, which requires from/to nodemasks for attach to be globally scoped
(though per-cpuset would work too) to persist from its pre_attach to
attach_task and attach.

This is a pre-patch for cgroup-procs-writable.patch.

Signed-off-by: Ben Blum 
Cc: "Eric W. Biederman" 
Cc: Li Zefan 
Cc: Matt Helsley 
Reviewed-by: Paul Menage 
Cc: Oleg Nesterov 
Cc: David Rientjes 
Cc: Miao Xie 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2011-05-23T19:53:48+00:00

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched: Increase SCHED_LOAD_SCALE resolution
  sched: Introduce SCHED_POWER_SCALE to scale cpu_power calculations
  sched: Cleanup set_load_weight()

Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc-next-2.6

2011-05-23T05:06:24+00:00

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc-next-2.6: (28 commits)
  sparc32: fix build, fix missing cpu_relax declaration
  SCHED_TTWU_QUEUE is not longer needed since sparc32 now implements IPI
  sparc32,leon: Remove unnecessary page_address calls in LEON DMA API.
  sparc: convert old cpumask API into new one
  sparc32, sun4d: Implemented SMP IPIs support for SUN4D machines
  sparc32, sun4m: Implemented SMP IPIs support for SUN4M machines
  sparc32,leon: Implemented SMP IPIs for LEON CPU
  sparc32: implement SMP IPIs using the generic functions
  sparc32,leon: SMP power down implementation
  sparc32,leon: added some SMP comments
  sparc: add {read,write}*_be routines
  sparc32,leon: don't rely on bootloader to mask IRQs
  sparc32,leon: operate on boot-cpu IRQ controller registers
  sparc32: always define boot_cpu_id
  sparc32: removed unused code, implemented by generic code
  sparc32: avoid build warning at mm/percpu.c:1647
  sparc32: always register a PROM based early console
  sparc32: probe for cpu info only during startup
  sparc: consolidate show_cpuinfo in cpu.c
  sparc32,leon: implement genirq CPU affinity
  ...

SCHED_TTWU_QUEUE is not longer needed since sparc32 now implements IPI

2011-05-20T20:10:55+00:00

Signed-off-by: Daniel Hellstrom 
Reported-by: Peter Zijlstra 
Acked-by: Peter Zijlstra 
Signed-off-by: David S. Miller

Merge commit '317f394160e9beb97d19a84c39b7e5eb3d7815a8'

2011-05-20T20:10:22+00:00

Conflicts:
	arch/sparc/kernel/smp_32.c

With merge conflict help from Daniel Hellstrom.

Signed-off-by: David S. Miller

sched: Increase SCHED_LOAD_SCALE resolution

2011-05-20T12:16:50+00:00

Introduce SCHED_LOAD_RESOLUTION, which scales is added to
SCHED_LOAD_SHIFT and increases the resolution of
SCHED_LOAD_SCALE. This patch sets the value of
SCHED_LOAD_RESOLUTION to 10, scaling up the weights for all
sched entities by a factor of 1024. With this extra resolution,
we can handle deeper cgroup hiearchies and the scheduler can do
better shares distribution and load load balancing on larger
systems (especially for low weight task groups).

This does not change the existing user interface, the scaled
weights are only used internally. We do not modify
prio_to_weight values or inverses, but use the original weights
when calculating the inverse which is used to scale execution
time delta in calc_delta_mine(). This ensures we do not lose
accuracy when accounting time to the sched entities. Thanks to
Nikunj Dadhania for fixing an bug in c_d_m() that broken fairness.

Below is some analysis of the performance costs/improvements of
this patch.

1. Micro-arch performance costs:

Experiment was to run Ingo's pipe_test_100k 200 times with the
task pinned to one cpu. I measured instruction, cycles and
stalled-cycles for the runs. See:

   http://thread.gmane.org/gmane.linux.kernel/1129232/focus=1129389

for more info.

-tip (baseline):

 Performance counter stats for '/root/load-scale/pipe-test-100k' (200 runs):

       964,991,769 instructions             #    0.82  insns per cycle
                                            #    0.33  stalled cycles per insn
                                            #    ( +-  0.05% )
     1,171,186,635 cycles                   #    0.000 GHz                      ( +-  0.08% )
       306,373,664 stalled-cycles-backend   #   26.16% backend  cycles idle     ( +-  0.28% )
       314,933,621 stalled-cycles-frontend  #   26.89% frontend cycles idle     ( +-  0.34% )

        1.122405684  seconds time elapsed  ( +-  0.05% )

-tip+patches:

 Performance counter stats for './load-scale/pipe-test-100k' (200 runs):

       963,624,821 instructions             #    0.82  insns per cycle
                                            #    0.33  stalled cycles per insn
                                            #    ( +-  0.04% )
     1,175,215,649 cycles                   #    0.000 GHz                      ( +-  0.08% )
       315,321,126 stalled-cycles-backend   #   26.83% backend  cycles idle     ( +-  0.28% )
       316,835,873 stalled-cycles-frontend  #   26.96% frontend cycles idle     ( +-  0.29% )

        1.122238659  seconds time elapsed  ( +-  0.06% )

With this patch, instructions decrease by ~0.10% and cycles
increase by 0.27%. This doesn't look statistically significant.
The number of stalled cycles in the backend increased from
26.16% to 26.83%. This can be attributed to the shifts we do in
c_d_m() and other places. The fraction of stalled cycles in the
frontend remains about the same, at 26.96% compared to 26.89% in -tip.

2. Balancing low-weight task groups

Test setup: run 50 tasks with random sleep/busy times (biased
around 100ms) in a low weight container (with cpu.shares = 2).
Measure %idle as reported by mpstat over a 10s window.

-tip (baseline):

06:47:48 PM  CPU    %usr   %nice    %sys %iowait    %irq   %soft  %steal  %guest   %idle    intr/s
06:47:49 PM  all   94.32    0.00    0.06    0.00    0.00    0.00    0.00    0.00    5.62  15888.00
06:47:50 PM  all   94.57    0.00    0.62    0.00    0.00    0.00    0.00    0.00    4.81  16180.00
06:47:51 PM  all   94.69    0.00    0.06    0.00    0.00    0.00    0.00    0.00    5.25  15966.00
06:47:52 PM  all   95.81    0.00    0.00    0.00    0.00    0.00    0.00    0.00    4.19  16053.00
06:47:53 PM  all   94.88    0.06    0.00    0.00    0.00    0.00    0.00    0.00    5.06  15984.00
06:47:54 PM  all   93.31    0.00    0.00    0.00    0.00    0.00    0.00    0.00    6.69  15806.00
06:47:55 PM  all   94.19    0.00    0.06    0.00    0.00    0.00    0.00    0.00    5.75  15896.00
06:47:56 PM  all   92.87    0.00    0.00    0.00    0.00    0.00    0.00    0.00    7.13  15716.00
06:47:57 PM  all   94.88    0.00    0.00    0.00    0.00    0.00    0.00    0.00    5.12  15982.00
06:47:58 PM  all   95.44    0.00    0.00    0.00    0.00    0.00    0.00    0.00    4.56  16075.00
Average:     all   94.49    0.01    0.08    0.00    0.00    0.00    0.00    0.00    5.42  15954.60

-tip+patches:

06:47:03 PM  CPU    %usr   %nice    %sys %iowait    %irq   %soft  %steal  %guest   %idle    intr/s
06:47:04 PM  all  100.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00  16630.00
06:47:05 PM  all   99.69    0.00    0.00    0.00    0.00    0.00    0.00    0.00    0.31  16580.20
06:47:06 PM  all   99.69    0.00    0.06    0.00    0.00    0.00    0.00    0.00    0.25  16596.00
06:47:07 PM  all   99.20    0.00    0.74    0.00    0.00    0.06    0.00    0.00    0.00  17838.61
06:47:08 PM  all  100.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00  16540.00
06:47:09 PM  all  100.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00  16575.00
06:47:10 PM  all  100.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00  16614.00
06:47:11 PM  all   99.94    0.00    0.00    0.00    0.00    0.00    0.00    0.00    0.06  16588.00
06:47:12 PM  all   99.94    0.00    0.06    0.00    0.00    0.00    0.00    0.00    0.00  16593.00
06:47:13 PM  all   99.94    0.00    0.06    0.00    0.00    0.00    0.00    0.00    0.00  16551.00
Average:     all   99.84    0.00    0.09    0.00    0.00    0.01    0.00    0.00    0.06  16711.58

We see an improvement in idle% on the system (drops from 5.42% on -tip to 0.06%
with the patches).

We see an improvement in idle% on the system (drops from 5.42%
on -tip to 0.06% with the patches).

Signed-off-by: Nikhil Rao 
Acked-by: Peter Zijlstra 
Cc: Nikunj A. Dadhania 
Cc: Srivatsa Vaddagiri 
Cc: Stephan Barwolf 
Cc: Mike Galbraith 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Link: http://lkml.kernel.org/r/1305754668-18792-1-git-send-email-ncrao@google.com
Signed-off-by: Ingo Molnar

sched: Introduce SCHED_POWER_SCALE to scale cpu_power calculations

2011-05-20T12:16:50+00:00

SCHED_LOAD_SCALE is used to increase nice resolution and to
scale cpu_power calculations in the scheduler. This patch
introduces SCHED_POWER_SCALE and converts all uses of
SCHED_LOAD_SCALE for scaling cpu_power to use SCHED_POWER_SCALE
instead.

This is a preparatory patch for increasing the resolution of
SCHED_LOAD_SCALE, and there is no need to increase resolution
for cpu_power calculations.

Signed-off-by: Nikhil Rao 
Acked-by: Peter Zijlstra 
Cc: Nikunj A. Dadhania 
Cc: Srivatsa Vaddagiri 
Cc: Stephan Barwolf 
Cc: Mike Galbraith 
Link: http://lkml.kernel.org/r/1305738580-9924-3-git-send-email-ncrao@google.com
Signed-off-by: Ingo Molnar

sched: Cleanup set_load_weight()

2011-05-20T12:16:49+00:00

Avoid using long repetitious names; make this simpler and nicer
to read. No functional change introduced in this patch.

Signed-off-by: Nikhil Rao 
Acked-by: Peter Zijlstra 
Cc: Nikunj A. Dadhania 
Cc: Srivatsa Vaddagiri 
Cc: Stephan Barwolf 
Cc: Mike Galbraith 
Link: http://lkml.kernel.org/r/1305738580-9924-2-git-send-email-ncrao@google.com
Signed-off-by: Ingo Molnar