The patch titled
memcg: simplify force_empty and move_lists
has been added to the -mm tree. Its filename is
memcg-simplify-force_empty-and-move_lists.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/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: simplify force_empty and move_lists
From: Hirokazu Takahashi <taka@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: YAMAMOTO Takashi <yamamoto@xxxxxxxxxxxxx>
Cc: Paul Menage <menage@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 62 +++++++++-------------------------------------
1 file changed, 13 insertions(+), 49 deletions(-)
diff -puN mm/memcontrol.c~memcg-simplify-force_empty-and-move_lists mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-simplify-force_empty-and-move_lists
+++ a/mm/memcontrol.c
@@ -353,7 +353,6 @@ int task_in_mem_cgroup(struct task_struc
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 *
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 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(
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;
- }
}
/*
_
Patches currently in -mm which might be from taka@xxxxxxxxxxxxx are
memcg-mm_match_cgroup-not-vm_match_cgroup.patch
memcg-move_lists-on-page-not-page_cgroup.patch
memcg-page_cache_release-not-__free_page.patch
memcg-when-do_swaps-do_wp_page-fails.patch
memcg-fix-vm_bug_on-from-page-migration.patch
memcg-bad-page-if-page_cgroup-when-free.patch
memcg-mem_cgroup_charge-never-null.patch
memcg-remove-mem_cgroup_uncharge.patch
memcg-memcontrol-whitespace-cleanups.patch
memcg-memcontrol-uninlined-and-static.patch
memcg-remove-clear_page_cgroup-and-atomics.patch
memcg-css_put-after-remove_list.patch
memcg-fix-mem_cgroup_move_lists-locking.patch
memcg-simplify-force_empty-and-move_lists.patch
-
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
