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memcg: make threshold index in the right position 

Index current_threshold may point to threshold that just equal to usage
after last call of __mem_cgroup_threshold.  But after registering a new
event, it will change (pointing to threshold just below usage).  So make
it consistent here.

For example:
now:
	threshold array:  3  [5]  7  9   (usage = 6, [index] = 5)

next turn (after calling __mem_cgroup_threshold):
	threshold array:  3   5  [7]  9   (usage = 7, [index] = 7)

after registering a new event (threshold = 10):
	threshold array:  3  [5]  7  9  10 (usage = 7, [index] = 5)

Signed-off-by: Sha Zhengju <handai.szj@taobao.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Sha Zhengju 2012-05-29 15:06:57 -07:00 committed by Linus Torvalds
parent a0db00fcf5
commit 748dad36d6
1 changed files with 6 additions and 5 deletions
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11
mm/memcontrol.c
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@ -181,7 +181,7 @@ struct mem_cgroup_threshold {
/* For threshold */
struct mem_cgroup_threshold_ary {
/* An array index points to threshold just below usage. */
/* An array index points to threshold just below or equal to usage. */
int current_threshold;
/* Size of entries[] */
unsigned int size;
@ -4280,7 +4280,7 @@ static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap)
usage = mem_cgroup_usage(memcg, swap);
/*
* current_threshold points to threshold just below usage.
* current_threshold points to threshold just below or equal to usage.
* If it's not true, a threshold was crossed after last
* call of __mem_cgroup_threshold().
*/
@ -4406,14 +4406,15 @@ static int mem_cgroup_usage_register_event(struct cgroup *cgrp,
/* Find current threshold */
new->current_threshold = -1;
for (i = 0; i < size; i++) {
if (new->entries[i].threshold < usage) {
if (new->entries[i].threshold <= usage) {
/*
* new->current_threshold will not be used until
* rcu_assign_pointer(), so it's safe to increment
* it here.
*/
++new->current_threshold;
}
} else
break;
}
/* Free old spare buffer and save old primary buffer as spare */
@ -4482,7 +4483,7 @@ static void mem_cgroup_usage_unregister_event(struct cgroup *cgrp,
continue;
new->entries[j] = thresholds->primary->entries[i];
if (new->entries[j].threshold < usage) {
if (new->entries[j].threshold <= usage) {
/*
* new->current_threshold will not be used
* until rcu_assign_pointer(), so it's safe to increment