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e75c8b475e
linux/kernel/sched
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Ingo Molnar e75c8b475e Merge branch 'sched/core' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks into sched/core 
Pull CPU runtime stats/accounting fixes from Frederic Weisbecker:

 " Some users are complaining that their threadgroup's runtime accounting
   freezes after a week or so of intense cpu-bound workload. This set tries
   to fix the issue by reducing the risk of multiplication overflow in the
   cputime scaling code. "

Stanislaw Gruszka further explained the historic context and impact of the
bug:

 " Commit 0cf55e1ec0 start to use scalling
   for whole thread group, so increase chances of hitting multiplication
   overflow, depending on how many CPUs are on the system.

   We have multiplication utime * rtime for one thread since commit
   b27f03d4bd.

   Overflow will happen after:

   rtime * utime > 0xffffffffffffffff jiffies

   if thread utilize 100% of CPU time, that gives:

   rtime > sqrt(0xffffffffffffffff) jiffies

   ritme > sqrt(0xffffffffffffffff) / (24 * 60 * 60 * HZ) days

   For HZ 100 it will be 497 days for HZ 1000 it will be 49 days.

   Bug affect only users, who run CPU intensive application for that
   long period. Also they have to be interested on utime,stime values,
   as bug has no other visible effect as making those values incorrect. "

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2013-03-18 10:09:31 +01:00
..
auto_group.c sched: split out css_online/css_offline from tg creation/destruction 2013-01-24 12:05:18 -08:00
auto_group.h Revert "sched/autogroup: Fix crash on reboot when autogroup is disabled" 2012-12-11 10:23:45 +01:00
clock.c
core.c Merge branch 'sched/cputime' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks into sched/core 2013-03-08 16:41:22 +01:00
cpupri.c sched/rt: Move rt specific bits into new header file 2013-02-07 20:51:08 +01:00
cpupri.h
cputime.c sched: Lower chances of cputime scaling overflow 2013-03-13 18:18:14 +01:00
debug.c Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-26 19:42:08 -08:00
fair.c sched: Fix variable name misnomer, add comments 2013-03-14 08:22:29 +01:00
features.h Automatic NUMA Balancing V11 2012-12-16 15:18:08 -08:00
idle_task.c sched/nohz: Rewrite and fix load-avg computation -- again 2012-07-05 20:58:13 +02:00
Makefile sched: Move cputime code to its own file 2012-08-20 13:05:17 +02:00
rt.c Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-19 18:19:48 -08:00
sched.h sched: Fix update_group_power() prototype placement to fix build warning when !CONFIG_SMP 2013-03-11 09:07:24 +01:00
stats.c sched: Fix /proc/sched_stat failure on very very large systems 2013-02-22 10:27:24 +01:00
stats.h
stop_task.c sched: Fix migration thread runtime bogosity 2012-08-13 18:41:55 +02:00