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authorHirokazu Takahashi <taka@valinux.co.jp>2008-03-04 14:29:15 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-03-04 16:35:15 -0800
commit9b3c0a07e0fca35e36751680de3e4c76dbff5df3 (patch)
tree3dd6355a88282ea5577a05b7f2d2d3ae216ab9a8
parent2680eed723b664d83e6181ae275fac0ec8fa05ff (diff)
downloadkernel-9b3c0a07e0fca35e36751680de3e4c76dbff5df3.tar.gz
memcg: simplify force_empty and move_lists
As for force_empty, though this may not be the main topic here, mem_cgroup_force_empty_list() can be implemented simpler. It is possible to make the function just call mem_cgroup_uncharge_page() instead of releasing page_cgroups by itself. The tip is to call get_page() before invoking mem_cgroup_uncharge_page(), so the page won't be released during this function. Kamezawa-san points out that by the time mem_cgroup_uncharge_page() uncharges, the page might have been reassigned to an lru of a different mem_cgroup, and now be emptied from that; but Hugh claims that's okay, the end state is the same as when it hasn't gone to another list. And once force_empty stops taking lock_page_cgroup within mz->lru_lock, mem_cgroup_move_lists() can be simplified to take mz->lru_lock directly while holding page_cgroup lock (but still has to use try_lock_page_cgroup). Signed-off-by: Hirokazu Takahashi <taka@valinux.co.jp> Signed-off-by: Hugh Dickins <hugh@veritas.com> Cc: David Rientjes <rientjes@google.com> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp> Cc: Paul Menage <menage@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/memcontrol.c62
1 files changed, 13 insertions, 49 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index dcbe30aad1da..f72067094e05 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -353,7 +353,6 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
void mem_cgroup_move_lists(struct page *page, bool active)
{
struct page_cgroup *pc;
- struct mem_cgroup *mem;
struct mem_cgroup_per_zone *mz;
unsigned long flags;
@@ -367,35 +366,14 @@ void mem_cgroup_move_lists(struct page *page, bool active)
if (!try_lock_page_cgroup(page))
return;
- /*
- * Now page_cgroup is stable, but we cannot acquire mz->lru_lock
- * while holding it, because mem_cgroup_force_empty_list does the
- * reverse. Get a hold on the mem_cgroup before unlocking, so that
- * the zoneinfo remains stable, then take mz->lru_lock; then check
- * that page still points to pc and pc (even if freed and reassigned
- * to that same page meanwhile) still points to the same mem_cgroup.
- * Then we know mz still points to the right spinlock, so it's safe
- * to move_lists (page->page_cgroup might be reset while we do so, but
- * that doesn't matter: pc->page is stable till we drop mz->lru_lock).
- * We're being a little naughty not to try_lock_page_cgroup again
- * inside there, but we are safe, aren't we? Aren't we? Whistle...
- */
pc = page_get_page_cgroup(page);
if (pc) {
- mem = pc->mem_cgroup;
mz = page_cgroup_zoneinfo(pc);
- css_get(&mem->css);
-
- unlock_page_cgroup(page);
-
spin_lock_irqsave(&mz->lru_lock, flags);
- if (page_get_page_cgroup(page) == pc && pc->mem_cgroup == mem)
- __mem_cgroup_move_lists(pc, active);
+ __mem_cgroup_move_lists(pc, active);
spin_unlock_irqrestore(&mz->lru_lock, flags);
-
- css_put(&mem->css);
- } else
- unlock_page_cgroup(page);
+ }
+ unlock_page_cgroup(page);
}
/*
@@ -789,7 +767,7 @@ static void mem_cgroup_force_empty_list(struct mem_cgroup *mem,
{
struct page_cgroup *pc;
struct page *page;
- int count;
+ int count = FORCE_UNCHARGE_BATCH;
unsigned long flags;
struct list_head *list;
@@ -798,35 +776,21 @@ static void mem_cgroup_force_empty_list(struct mem_cgroup *mem,
else
list = &mz->inactive_list;
- if (list_empty(list))
- return;
-retry:
- count = FORCE_UNCHARGE_BATCH;
spin_lock_irqsave(&mz->lru_lock, flags);
-
- while (--count && !list_empty(list)) {
+ while (!list_empty(list)) {
pc = list_entry(list->prev, struct page_cgroup, lru);
page = pc->page;
- lock_page_cgroup(page);
- if (page_get_page_cgroup(page) == pc) {
- page_assign_page_cgroup(page, NULL);
- unlock_page_cgroup(page);
- __mem_cgroup_remove_list(pc);
- res_counter_uncharge(&mem->res, PAGE_SIZE);
- css_put(&mem->css);
- kfree(pc);
- } else {
- /* racing uncharge: let page go then retry */
- unlock_page_cgroup(page);
- break;
+ get_page(page);
+ spin_unlock_irqrestore(&mz->lru_lock, flags);
+ mem_cgroup_uncharge_page(page);
+ put_page(page);
+ if (--count <= 0) {
+ count = FORCE_UNCHARGE_BATCH;
+ cond_resched();
}
+ spin_lock_irqsave(&mz->lru_lock, flags);
}
-
spin_unlock_irqrestore(&mz->lru_lock, flags);
- if (!list_empty(list)) {
- cond_resched();
- goto retry;
- }
}
/*