Peter Zijlstra 19a78d110d sched/numa: Mitigate chance that same task always updates PTEs ... With a trace_printk("working\n"); right after the cmpxchg in task_numa_work() we can see that of a 4 thread process, its always the same task winning the race and doing the protection change. This is a problem since the task doing the protection change has a penalty for taking faults -- it is busy when marking the PTEs. If its always the same task the ->numa_faults[] get severely skewed. Avoid this by delaying the task doing the protection change such that it is unlikely to win the privilege again. Before: root@interlagos:~# grep "thread 0/.*working" /debug/tracing/trace | tail -15 thread 0/0-3232 [022] .... 212.787402: task_numa_work: working thread 0/0-3232 [022] .... 212.888473: task_numa_work: working thread 0/0-3232 [022] .... 212.989538: task_numa_work: working thread 0/0-3232 [022] .... 213.090602: task_numa_work: working thread 0/0-3232 [022] .... 213.191667: task_numa_work: working thread 0/0-3232 [022] .... 213.292734: task_numa_work: working thread 0/0-3232 [022] .... 213.393804: task_numa_work: working thread 0/0-3232 [022] .... 213.494869: task_numa_work: working thread 0/0-3232 [022] .... 213.596937: task_numa_work: working thread 0/0-3232 [022] .... 213.699000: task_numa_work: working thread 0/0-3232 [022] .... 213.801067: task_numa_work: working thread 0/0-3232 [022] .... 213.903155: task_numa_work: working thread 0/0-3232 [022] .... 214.005201: task_numa_work: working thread 0/0-3232 [022] .... 214.107266: task_numa_work: working thread 0/0-3232 [022] .... 214.209342: task_numa_work: working After: root@interlagos:~# grep "thread 0/.*working" /debug/tracing/trace | tail -15 thread 0/0-3253 [005] .... 136.865051: task_numa_work: working thread 0/2-3255 [026] .... 136.965134: task_numa_work: working thread 0/3-3256 [024] .... 137.065217: task_numa_work: working thread 0/3-3256 [024] .... 137.165302: task_numa_work: working thread 0/3-3256 [024] .... 137.265382: task_numa_work: working thread 0/0-3253 [004] .... 137.366465: task_numa_work: working thread 0/2-3255 [026] .... 137.466549: task_numa_work: working thread 0/0-3253 [004] .... 137.566629: task_numa_work: working thread 0/0-3253 [004] .... 137.666711: task_numa_work: working thread 0/1-3254 [028] .... 137.766799: task_numa_work: working thread 0/0-3253 [004] .... 137.866876: task_numa_work: working thread 0/2-3255 [026] .... 137.966960: task_numa_work: working thread 0/1-3254 [028] .... 138.067041: task_numa_work: working thread 0/2-3255 [026] .... 138.167123: task_numa_work: working thread 0/3-3256 [024] .... 138.267207: task_numa_work: working Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Rik van Riel <riel@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Link: http://lkml.kernel.org/r/1381141781-10992-14-git-send-email-mgorman@suse.de Signed-off-by: Ingo Molnar <mingo@kernel.org>		2013-10-09 12:39:56 +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	sched: Prepare for per-cpu preempt_count	2013-09-25 14:07:55 +02:00
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
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/numa: Mitigate chance that same task always updates PTEs	2013-10-09 12:39:56 +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: Remove redundant nr_cpus_allowed test	2013-10-06 11:28:40 +02:00
sched.h	sched/balancing: Consider max cost of idle balance per sched domain	2013-09-20 12:03:44 +02:00
stats.c	fix a leak in /proc/schedstats	2013-04-29 15:41:45 -04:00
stats.h	sched: Micro-optimize by dropping unnecessary task_rq() calls	2013-09-25 13:51:06 +02:00
stop_task.c	sched: Use an accessor to read the rq clock	2013-05-28 09:40:27 +02:00