From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx101.postini.com [74.125.245.101]) by kanga.kvack.org (Postfix) with SMTP id D7B086B004F for ; Mon, 19 Dec 2011 10:37:43 -0500 (EST) Date: Mon, 19 Dec 2011 16:37:38 +0100 From: Johannes Weiner Subject: Re: [PATCH 3/4] memcg: clear pc->mem_cgorup if necessary. Message-ID: <20111219153738.GC1415@cmpxchg.org> References: <20111214164734.4d7d6d97.kamezawa.hiroyu@jp.fujitsu.com> <20111214165124.4d2cf723.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111214165124.4d2cf723.kamezawa.hiroyu@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org List-ID: To: KAMEZAWA Hiroyuki Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Michal Hocko , "akpm@linux-foundation.org" , Hugh Dickins , Ying Han On Wed, Dec 14, 2011 at 04:51:24PM +0900, KAMEZAWA Hiroyuki wrote: > From: KAMEZAWA Hiroyuki > > This is a preparation before removing a flag PCG_ACCT_LRU in page_cgroup > and reducing atomic ops/complexity in memcg LRU handling. > > In some cases, pages are added to lru before charge to memcg and pages > are not classfied to memory cgroup at lru addtion. Now, the lru where > the page should be added is determined a bit in page_cgroup->flags and > pc->mem_cgroup. I'd like to remove the check of flag. > > To handle the case pc->mem_cgroup may contain stale pointers if pages are > added to LRU before classification. This patch resets pc->mem_cgroup to > root_mem_cgroup before lru additions. > > Signed-off-by: KAMEZAWA Hiroyuki The followup compilation fixes aside, I agree. But the sites where the owner is actually reset are really not too obvious. How about the comment patch below? Otherwise, Acked-by: Johannes Weiner --- From: Johannes Weiner Subject: memcg: clear pc->mem_cgorup if necessary fix Add comments to the clearing sites. Signed-off-by: Johannes Weiner --- diff --git a/mm/ksm.c b/mm/ksm.c index 5c2f0bd..f0ee5bf 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -1571,6 +1571,15 @@ struct page *ksm_does_need_to_copy(struct page *page, new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); if (new_page) { + /* + * The memcg-specific accounting when moving + * pages around the LRU lists relies on the + * page's owner (memcg) to be valid. Usually, + * pages are assigned to a new owner before + * being put on the LRU list, but since this + * is not the case here, the stale owner from + * a previous allocation cycle must be reset. + */ mem_cgroup_reset_owner(new_page); copy_user_highpage(new_page, page, address, vma); diff --git a/mm/swap_state.c b/mm/swap_state.c index 730c4c7..44ccfd2 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -302,6 +302,15 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, new_page = alloc_page_vma(gfp_mask, vma, addr); if (!new_page) break; /* Out of memory */ + /* + * The memcg-specific accounting when moving + * pages around the LRU lists relies on the + * page's owner (memcg) to be valid. Usually, + * pages are assigned to a new owner before + * being put on the LRU list, but since this + * is not the case here, the stale owner from + * a previous allocation cycle must be reset. + */ mem_cgroup_reset_owner(new_page); } -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org