On 02/02/2012 06:54 PM, Sha Zhengju wrote:
On 02/02/2012 06:14 PM, Kirill A. Shutemov wrote:
On Thu, Feb 02, 2012 at 05:45:19PM +0800, Sha Zhengju wrote:
From: Sha Zhengju<handai.szj@xxxxxxxxxx>
Index current_threshold may point to threshold that just equal to
usage after __mem_cgroup_threshold is triggerd.
I don't see it. Could you describe conditions?
It is because of the following code path in __mem_cgroup_threshold:
{
...
i = t->current_threshold;
for (; i >= 0 && unlikely(t->entries[i].threshold > usage); i--)
eventfd_signal(t->entries[i].eventfd, 1);
i++;
for (; i < t->size && unlikely(t->entries[i].threshold <=
usage); i++)
eventfd_signal(t->entries[i].eventfd, 1);
t->current_threshold = i - 1;
...
}
For example:
now:
threshold array: 3 5 7 9 (usage = 6)
^
index
next turn:
threshold array: 3 5 7 9 (usage = 7)
^
index
after registering a new event(threshold = 10):
threshold array: 3 5 7 9 10 (usage = 7)
^
index
Err.. Sorry for showing inaccurate index position... (may because of the
mail format)
now:
threshold array: 3 [5] 7 9 (usage = 6, index = 5)
next turn:
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)
But after registering
a new event, it will change (pointing to threshold just below usage).
So make it consistent here.
Cc: KAMEZAWA Hiroyuki<kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Kirill A. Shutemov<kirill@xxxxxxxxxxxxx>
Signed-off-by: Sha Zhengju<handai.szj@xxxxxxxxxx>
---
mm/memcontrol.c | 7 ++++---
1 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 22d94f5..79f4a58 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -183,7 +183,7 @@ 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;
@@ -4319,14 +4319,15 @@ 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 */
--
1.7.4.1
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