The patch titled
memcg: remove unneeded preempt_disable
has been added to the -mm tree. Its filename is
memcg-remove-unneeded-preempt_disable.patch
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See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: memcg: remove unneeded preempt_disable
From: Greg Thelen <gthelen@xxxxxxxxxx>
Both mem_cgroup_charge_statistics() and mem_cgroup_move_account() were
unnecessarily disabling preemption when adjusting per-cpu counters:
preempt_disable()
__this_cpu_xxx()
__this_cpu_yyy()
preempt_enable()
This change does not disable preemption and thus CPU switch is possible
within these routines. This does not cause a problem because the total
of all cpu counters is summed when reporting stats. Now both
mem_cgroup_charge_statistics() and mem_cgroup_move_account() look like:
this_cpu_xxx()
this_cpu_yyy()
akpm: this is an optimisation for x86 and a deoptimisation for non-x86.
The non-x86 situation will be fixed as architectures implement their
atomic this_cpu_foo() operations.
Signed-off-by: Greg Thelen <gthelen@xxxxxxxxxx>
Reported-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Johannes Weiner <jweiner@xxxxxxxxxx>
Cc: Valdis Kletnieks <Valdis.Kletnieks@xxxxxx>
Cc: Balbir Singh <bsingharora@xxxxxxxxx>
Cc: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 24 +++++++++---------------
1 file changed, 9 insertions(+), 15 deletions(-)
diff -puN mm/memcontrol.c~memcg-remove-unneeded-preempt_disable mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-remove-unneeded-preempt_disable
+++ a/mm/memcontrol.c
@@ -664,26 +664,22 @@ static unsigned long mem_cgroup_read_eve
static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
bool file, int nr_pages)
{
- preempt_disable();
-
if (file)
- __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_CACHE],
+ this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_CACHE],
nr_pages);
else
- __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_RSS],
+ this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_RSS],
nr_pages);
/* pagein of a big page is an event. So, ignore page size */
- if (nr_pages > 0)
- __this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PGPGIN]);
- else {
- __this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PGPGOUT]);
+ if (nr_pages > 0) {
+ this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PGPGIN]);
+ } else {
+ this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PGPGOUT]);
nr_pages = -nr_pages; /* for event */
}
- __this_cpu_add(memcg->stat->events[MEM_CGROUP_EVENTS_COUNT], nr_pages);
-
- preempt_enable();
+ this_cpu_add(memcg->stat->events[MEM_CGROUP_EVENTS_COUNT], nr_pages);
}
unsigned long
@@ -2711,10 +2707,8 @@ static int mem_cgroup_move_account(struc
if (PageCgroupFileMapped(pc)) {
/* Update mapped_file data for mem_cgroup */
- preempt_disable();
- __this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
- __this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
- preempt_enable();
+ this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
+ this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
}
mem_cgroup_charge_statistics(from, PageCgroupCache(pc), -nr_pages);
if (uncharge)
_
Patches currently in -mm which might be from gthelen@xxxxxxxxxx are
memcg-remove-unneeded-preempt_disable.patch
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