From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [patch] mm: memcontrol: clarify migration where old page is uncharged Date: Mon, 20 Oct 2014 21:45:05 +0200 Message-ID: <20141020194505.GE505@dhcp22.suse.cz> References: <1413732647-16043-1-git-send-email-hannes@cmpxchg.org> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; bh=jxPPhEjtaLkmCgs5u+XfgOTzM7crnvfC6xgAuL9j6Vo=; b=ZGxbBO1iaKSQu8OlN+7JXSOav9WOQtWwc5L2MNv+CWvg9oBcGtdCCjIYBFfUpfBEfX R+ERcruO78FGX18yhFDv7lFuLmlSjUQLqNwlxxBVRH/Aei1LbsHBTyR4Q8TltrHf06zt 0DQlpGYw/ExRMnp4ksRD/IHibQAoSucdPNZYEOfDXRkz6CgtE0+v5SE9AEtt+fORrimL iHiJG9meWC6HqFgz8pMfgdF4BkYjtKx2ShctbIz8DGus2alAktigJbcQihBXrTkTGXgz /ghkIwep1VbayPcWYfCB9uRxqlHG123B74uXe+lcH0Q8LH4S1aiojw8IGaebd4xk7LqL f2og== Content-Disposition: inline In-Reply-To: <1413732647-16043-1-git-send-email-hannes@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Johannes Weiner Cc: Andrew Morton , Hugh Dickins , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org On Sun 19-10-14 11:30:47, Johannes Weiner wrote: > Better explain re-entrant migration when compaction races with > reclaim, and also mention swapcache readahead pages as possible > uncharged migration sources. > > Signed-off-by: Johannes Weiner Acked-by: Michal Hocko > --- > mm/memcontrol.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index fc1d7ca96b9d..76892eb89d26 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6166,7 +6166,12 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage, > if (PageCgroupUsed(pc)) > return; > > - /* Re-entrant migration: old page already uncharged? */ > + /* > + * Swapcache readahead pages can get migrated before being > + * charged, and migration from compaction can happen to an > + * uncharged page when the PFN walker finds a page that > + * reclaim just put back on the LRU but has not released yet. > + */ > pc = lookup_page_cgroup(oldpage); > if (!PageCgroupUsed(pc)) > return; > -- > 2.1.2 > -- Michal Hocko SUSE Labs -- 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