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Subject[RFC][PATCH 1/4] memcg: simplify page cache charging
This is an add-on patches to mem_cgroup_replace_page_cache(), introducing
new LRU rule under memcg, finally. After this, lru handling will be
much simplified. (all pathces are based on 3.2.0-rc4-next-20111205+)

But this is experimental... I may forget some important corner cases.
==
From 028eddd3fea1634e23b18a96ba5653e8c54b437b Mon Sep 17 00:00:00 2001
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Date: Tue, 6 Dec 2011 14:57:01 +0900
Subject: [PATCH 1/4] memcg: simplify page cache charging.

Because of commit ef6a3c6311, FUSE uses replace_page_cache() instead
of add_to_page_cache(). Then, mem_cgroup_cache_charge() is not
called against FUSE's pages from splice.

So, Now, mem_cgroup_cache_charge() doesn't receive a page on LRU
unless it's not SwapCache.
For checking, WARN_ON_ONCE(PageLRU(page)) is added.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
mm/memcontrol.c | 31 +++++++++----------------------
1 files changed, 9 insertions(+), 22 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a9e92a6..947c62c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2710,6 +2710,7 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
gfp_t gfp_mask)
{
struct mem_cgroup *memcg = NULL;
+ enum charge_type type = MEM_CGROUP_CHARGE_TYPE_CACHE;
int ret;

if (mem_cgroup_disabled())
@@ -2719,31 +2720,17 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,

if (unlikely(!mm))
mm = &init_mm;
+ if (!page_is_file_cache(page))
+ type = MEM_CGROUP_CHARGE_TYPE_SHMEM;

- if (page_is_file_cache(page)) {
- ret = __mem_cgroup_try_charge(mm, gfp_mask, 1, &memcg, true);
- if (ret || !memcg)
- return ret;
-
- /*
- * FUSE reuses pages without going through the final
- * put that would remove them from the LRU list, make
- * sure that they get relinked properly.
- */
- __mem_cgroup_commit_charge_lrucare(page, memcg,
- MEM_CGROUP_CHARGE_TYPE_CACHE);
- return ret;
- }
- /* shmem */
- if (PageSwapCache(page)) {
+ if (!PageSwapCache(page)) {
+ ret = mem_cgroup_charge_common(page, mm, gfp_mask, type);
+ WARN_ON_ONCE(PageLRU(page));
+ } else { /* page is swapcache/shmem */
ret = mem_cgroup_try_charge_swapin(mm, page, gfp_mask, &memcg);
if (!ret)
- __mem_cgroup_commit_charge_swapin(page, memcg,
- MEM_CGROUP_CHARGE_TYPE_SHMEM);
- } else
- ret = mem_cgroup_charge_common(page, mm, gfp_mask,
- MEM_CGROUP_CHARGE_TYPE_SHMEM);
-
+ __mem_cgroup_commit_charge_swapin(page, memcg, type);
+ }
return ret;
}

--
1.7.4.1



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