Re: [PATCH 1/4] memcg: simplify page cache charging.

Michal Hocko
2011-12-20T15:33:45Z

On Wed 14-12-11 16:49:22, KAMEZAWA Hiroyuki wrote:
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>
> This patch is a clean up. No functional/logical changes.
>
> 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.

too many negations makes it hard to read. What about:

mem_cgroup_cache_charge gets pages that are not on LRU with exception of
PageSwapCache pages.

> For checking, WARN_ON_ONCE(PageLRU(page)) is added.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Makes sense.
Acked-by: Michal Hocko <mhocko@suse.cz>

> ---
> 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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--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic