linux.git/kernel/sched/cputime.c, branch v3.11

Merge tag 'v3.10' into sched/core

2013-07-01T09:18:53+00:00

Merge in a recent upstream commit:

  c2853c8df57f include/linux/math64.h: add div64_ul()

because:

  72a4cf20cb71 sched: Change cfs_rq load avg to unsigned long

relies on it.

[ We don't rebase sched/core for this, because the handful of
  followup commits after the broken commit are not behavioral
  changes so are unlikely to be needed during bisection. ]

Signed-off-by: Ingo Molnar

vtime: Use consistent clocks among nohz accounting

2013-05-31T09:31:50+00:00

While computing the cputime delta of dynticks CPUs,
we are mixing up clocks of differents natures:

* local_clock() which takes care of unstable clock
sources and fix these if needed.

* sched_clock() which is the weaker version of
local_clock(). It doesn't compute any fixup in case
of unstable source.

If the clock source is stable, those two clocks are the
same and we can safely compute the difference against
two random points.

Otherwise it results in random deltas as sched_clock()
can randomly drift away, back or forward, from local_clock().

As a consequence, some strange behaviour with unstable tsc
has been observed such as non progressing constant zero cputime.
(The 'top' command showing no load).

Fix this by only using local_clock(), or its irq safe/remote
equivalent, in vtime code.

Reported-by: Mike Galbraith 
Suggested-by: Mike Galbraith 
Cc: Steven Rostedt 
Cc: Paul E. McKenney 
Cc: Ingo Molnar 
Cc: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: Borislav Petkov 
Cc: Li Zhong 
Cc: Mike Galbraith 
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Ingo Molnar

sched: Use swap() macro in scale_stime()

2013-05-28T09:58:10+00:00

Simple cleanup.

Reported-by: Peter Zijlstra 
Signed-off-by: Stanislaw Gruszka 
Cc: Frederic Weisbecker 
Link: http://lkml.kernel.org/r/1367501673-6563-1-git-send-email-sgruszka@redhat.com
Signed-off-by: Ingo Molnar

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

2013-05-02T21:56:31+00:00

Pull scheduler fixes from Ingo Molnar:
 "This fixes the cputime scaling overflow problems for good without
  having bad 32-bit overhead, and gets rid of the div64_u64_rem() helper
  as well."

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Revert "math64: New div64_u64_rem helper"
  sched: Avoid prev->stime underflow
  sched: Do not account bogus utime
  sched: Avoid cputime scaling overflow

sched: Avoid prev->stime underflow

2013-04-30T17:13:05+00:00

Dave Hansen reported strange utime/stime values on his system:
https://lkml.org/lkml/2013/4/4/435

This happens because prev->stime value is bigger than rtime
value. Root of the problem are non-monotonic rtime values (i.e.
current rtime is smaller than previous rtime) and that should be
debugged and fixed.

But since problem did not manifest itself before commit
62188451f0d63add7ad0cd2a1ae269d600c1663d "cputime: Avoid
multiplication overflow on utime scaling", it should be threated
as regression, which we can easily fixed on cputime_adjust()
function.

For now, let's apply this fix, but further work is needed to fix
root of the problem.

Reported-and-tested-by: Dave Hansen 
Cc:  # 3.9+
Signed-off-by: Stanislaw Gruszka 
Cc: Frederic Weisbecker 
Cc: rostedt@goodmis.org
Cc: Linus Torvalds 
Cc: Dave Hansen 
Cc: Peter Zijlstra 
Link: http://lkml.kernel.org/r/1367314507-9728-3-git-send-email-sgruszka@redhat.com
Signed-off-by: Ingo Molnar

sched: Do not account bogus utime

2013-04-30T17:13:04+00:00

Due to rounding in scale_stime(), for big numbers, scaled stime
values will grow in chunks. Since rtime grow in jiffies and we
calculate utime like below:

	prev->stime = max(prev->stime, stime);
	prev->utime = max(prev->utime, rtime - prev->stime);

we could erroneously account stime values as utime. To prevent
that only update prev->{u,s}time values when they are smaller
than current rtime.

Signed-off-by: Stanislaw Gruszka 
Cc: Frederic Weisbecker 
Cc: rostedt@goodmis.org
Cc: Linus Torvalds 
Cc: Dave Hansen 
Cc: Peter Zijlstra 
Link: http://lkml.kernel.org/r/1367314507-9728-2-git-send-email-sgruszka@redhat.com
Signed-off-by: Ingo Molnar

sched: Avoid cputime scaling overflow

2013-04-30T17:13:04+00:00

Here is patch, which adds Linus's cputime scaling algorithm to the
kernel.

This is a follow up (well, fix) to commit
d9a3c9823a2e6a543eb7807fb3d15d8233817ec5 ("sched: Lower chances
of cputime scaling overflow") which commit tried to avoid
multiplication overflow, but did not guarantee that the overflow
would not happen.

Linus crated a different algorithm, which completely avoids the
multiplication overflow by dropping precision when numbers are
big.

It was tested by me and it gives good relative error of
scaled numbers. Testing method is described here:
http://marc.info/?l=linux-kernel&m=136733059505406&w=2

Originally-From: Linus Torvalds 
Signed-off-by: Stanislaw Gruszka 
Cc: Frederic Weisbecker 
Cc: rostedt@goodmis.org
Cc: Dave Hansen 
Cc: Peter Zijlstra 
Link: http://lkml.kernel.org/r/20130430151441.GC10465@redhat.com
Signed-off-by: Ingo Molnar

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

2013-04-30T14:43:28+00:00

Pull scheduler changes from Ingo Molnar:
 "The main changes in this development cycle were:

   - full dynticks preparatory work by Frederic Weisbecker

   - factor out the cpu time accounting code better, by Li Zefan

   - multi-CPU load balancer cleanups and improvements by Joonsoo Kim

   - various smaller fixes and cleanups"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (45 commits)
  sched: Fix init NOHZ_IDLE flag
  sched: Prevent to re-select dst-cpu in load_balance()
  sched: Rename load_balance_tmpmask to load_balance_mask
  sched: Move up affinity check to mitigate useless redoing overhead
  sched: Don't consider other cpus in our group in case of NEWLY_IDLE
  sched: Explicitly cpu_idle_type checking in rebalance_domains()
  sched: Change position of resched_cpu() in load_balance()
  sched: Fix wrong rq's runnable_avg update with rt tasks
  sched: Document task_struct::personality field
  sched/cpuacct/UML: Fix header file dependency bug on the UML build
  cgroup: Kill subsys.active flag
  sched/cpuacct: No need to check subsys active state
  sched/cpuacct: Initialize cpuacct subsystem earlier
  sched/cpuacct: Initialize root cpuacct earlier
  sched/cpuacct: Allocate per_cpu cpuusage for root cpuacct statically
  sched/cpuacct: Clean up cpuacct.h
  sched/cpuacct: Remove redundant NULL checks in cpuacct_acount_field()
  sched/cpuacct: Remove redundant NULL checks in cpuacct_charge()
  sched/cpuacct: Add cpuacct_acount_field()
  sched/cpuacct: Add cpuacct_init()
  ...

sched/cpuacct: Add cpuacct_acount_field()

2013-04-10T11:54:17+00:00

So we can remove open-coded cpuacct code in cputime.c.

Signed-off-by: Li Zefan 
Acked-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/51553692.9060008@huawei.com
Signed-off-by: Ingo Molnar

sched/cputime: Fix accounting on multi-threaded processes

2013-04-08T15:40:52+00:00

Recent commit 6fac4829 ("cputime: Use accessors to read task
cputime stats") introduced a bug, where we account many times
the cputime of the first thread, instead of cputimes of all
the different threads.

Signed-off-by: Stanislaw Gruszka 
Acked-by: Frederic Weisbecker 
Cc: Oleg Nesterov 
Cc: Peter Zijlstra 
Link: http://lkml.kernel.org/r/20130404085740.GA2495@redhat.com
Signed-off-by: Ingo Molnar