From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx116.postini.com [74.125.245.116]) by kanga.kvack.org (Postfix) with SMTP id 33BB56B006C for ; Mon, 9 Jul 2012 16:11:56 -0400 (EDT) Received: by ggm4 with SMTP id 4so12903414ggm.14 for ; Mon, 09 Jul 2012 13:11:55 -0700 (PDT) Date: Mon, 9 Jul 2012 13:11:16 -0700 (PDT) From: Hugh Dickins Subject: Re: [patch 03/11] mm: shmem: do not try to uncharge known swapcache pages In-Reply-To: <1341449103-1986-4-git-send-email-hannes@cmpxchg.org> Message-ID: References: <1341449103-1986-1-git-send-email-hannes@cmpxchg.org> <1341449103-1986-4-git-send-email-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: Andrew Morton , KAMEZAWA Hiroyuki , Michal Hocko , David Rientjes , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org On Thu, 5 Jul 2012, Johannes Weiner wrote: > Once charged, swapcache pages can only be uncharged after they are > removed from swapcache again. > > Do not try to uncharge pages that are known to be in the swapcache, to > allow future patches to remove checks for that in the uncharge code. > > Signed-off-by: Johannes Weiner > --- > mm/shmem.c | 11 ++++++----- > 1 files changed, 6 insertions(+), 5 deletions(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index ee1c5a2..d12b705 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -302,8 +302,6 @@ static int shmem_add_to_page_cache(struct page *page, > if (!expected) > radix_tree_preload_end(); > } > - if (error) > - mem_cgroup_uncharge_cache_page(page); > return error; > } > > @@ -1184,11 +1182,14 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, > __set_page_locked(page); > error = mem_cgroup_cache_charge(page, current->mm, > gfp & GFP_RECLAIM_MASK); > - if (!error) > - error = shmem_add_to_page_cache(page, mapping, index, > - gfp, NULL); > if (error) > goto decused; > + error = shmem_add_to_page_cache(page, mapping, index, > + gfp, NULL); > + if (error) { > + mem_cgroup_uncharge_cache_page(page); > + goto decused; > + } > lru_cache_add_anon(page); > > spin_lock(&info->lock); > -- I wanted to try this series out on mmotm before replying, and that took a while; but the problems (some experimental RCU stuff, since reverted; and Michal's wait_on_page_writeback in vmscan.c, I'll have to investigate that later) were in mmotm rather than your series: seems to be running fine under load now. I've not reviewed, but definitely approve avoiding the temporary extra charge in migration, and your other simplifications. And I do approve this change, but selfishly withhold my Ack because it's a subset of small shmem.c changes I was already lining up to post, hoping still to sneak into 3.5. We have a real bug in there (charging to wrong memcg), and this cleanup comes along with that. I'll post my version in an hour or two. Hugh -- 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/ . Don't email: email@kvack.org