Vladimir Davydov 3029ede393 sched/balancing: Fix 'local->avg_load > busiest->avg_load' case in fix_small_imbalance() ...

In busiest->group_imb case we can come to fix_small_imbalance() with
local->avg_load > busiest->avg_load. This can result in wrong imbalance
fix-up, because there is the following check there where all the
members are unsigned:

if (busiest->avg_load - local->avg_load + scaled_busy_load_per_task >=
    (scaled_busy_load_per_task * imbn)) {
	env->imbalance = busiest->load_per_task;
	return;
}

As a result we can end up constantly bouncing tasks from one cpu to
another if there are pinned tasks.

Fix it by substituting the subtraction with an equivalent addition in
the check.

[ The bug can be caught by running 2*N cpuhogs pinned to two logical cpus
  belonging to different cores on an HT-enabled machine with N logical
  cpus: just look at se.nr_migrations growth. ]

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/ef167822e5c5b2d96cf5b0e3e4f4bdff3f0414a2.1379252740.git.vdavydov@parallels.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2013-09-20 11:59:38 +02:00

..

auto_group.c

sched/autogroup: Fix race with task_groups list

2013-05-28 09:40:22 +02:00

auto_group.h

Revert "sched/autogroup: Fix crash on reboot when autogroup is disabled"

2012-12-11 10:23:45 +01:00

clock.c

sched_clock: Prevent 64bit inatomicity on 32bit systems

2013-04-08 11:50:44 +02:00

core.c

Merge branch 'next' of git://git.kernel.org/pub/scm/virt/kvm/kvm

2013-09-04 18:15:06 -07:00

cpuacct.c

cgroup: pass around cgroup_subsys_state instead of cgroup in file methods

2013-08-08 20:11:24 -04:00

cpuacct.h

sched/cpuacct: Initialize root cpuacct earlier

2013-04-10 13:54:20 +02:00

cpupri.c

sched: Fix some kernel-doc warnings

2013-07-18 09:58:21 +02:00

cpupri.h

sched: Move all scheduler bits into kernel/sched/

2011-11-17 12:20:22 +01:00

cputime.c

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

2013-09-05 12:36:46 -07:00

debug.c

sched/debug: Take PID namespace into account

2013-09-12 19:14:16 +02:00

fair.c

sched/balancing: Fix 'local->avg_load > busiest->avg_load' case in fix_small_imbalance()

2013-09-20 11:59:38 +02:00

features.h

mutex: Move mutex spinning code from sched/core.c back to mutex.c

2013-04-19 09:33:34 +02:00

idle_task.c

sched: Keep at least 1 tick per second for active dynticks tasks

2013-05-04 08:32:02 +02:00

Makefile

sched: Factor out load calculation code from sched/core.c --> sched/proc.c

2013-05-07 13:14:50 +02:00

proc.c

sched: Change get_rq_runnable_load() to static and inline

2013-06-27 10:07:44 +02:00

rt.c

sched/rt: Simplify pull_rt_task() logic and remove .leaf_rt_rq_list

2013-06-19 12:58:40 +02:00

sched.h

Merge branches 'perf-urgent-for-linus' and 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2013-09-04 08:25:35 -07:00

stats.c

fix a leak in /proc/schedstats

2013-04-29 15:41:45 -04:00

stats.h

sched: Fix comment for sched_info_depart

2013-09-16 11:18:34 +02:00

stop_task.c

sched: Use an accessor to read the rq clock

2013-05-28 09:40:27 +02:00