From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id EC2F28D0039 for ; Thu, 27 Jan 2011 09:00:36 -0500 (EST) Date: Thu, 27 Jan 2011 16:00:24 +0200 From: Gleb Natapov Subject: Re: [patch 2/3] memcg: prevent endless loop on huge page charge Message-ID: <20110127140024.GR14750@redhat.com> References: <20110121153431.191134dd.kamezawa.hiroyu@jp.fujitsu.com> <20110121154430.70d45f15.kamezawa.hiroyu@jp.fujitsu.com> <20110127103438.GC2401@cmpxchg.org> <20110127134645.GA14309@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110127134645.GA14309@cmpxchg.org> Sender: owner-linux-mm@kvack.org To: Johannes Weiner Cc: KAMEZAWA Hiroyuki , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "nishimura@mxp.nes.nec.co.jp" , "balbir@linux.vnet.ibm.com" , "akpm@linux-foundation.org" List-ID: On Thu, Jan 27, 2011 at 02:46:45PM +0100, Johannes Weiner wrote: > The charging code can encounter a charge size that is bigger than a > regular page in two situations: one is a batched charge to fill the > per-cpu stocks, the other is a huge page charge. > > This code is distributed over two functions, however, and only the > outer one is aware of huge pages. In case the charging fails, the > inner function will tell the outer function to retry if the charge > size is bigger than regular pages--assuming batched charging is the > only case. And the outer function will retry forever charging a huge > page. > > This patch makes sure the inner function can distinguish between batch > charging and a single huge page charge. It will only signal another > attempt if batch charging failed, and go into regular reclaim when it > is called on behalf of a huge page. > Yeah, that is exactly the case I am debugging right now. Came up with different solution: pass page_size to __mem_cgroup_do_charge() and compare csize with page_size (not CHARGE_SIZE). Not sure which solution it more correct. > Signed-off-by: Johannes Weiner > --- > mm/memcontrol.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 8fa4be3..17c4e36 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -1847,7 +1847,7 @@ static int __mem_cgroup_do_charge(struct mem_cgroup *mem, gfp_t gfp_mask, > } else > mem_over_limit = mem_cgroup_from_res_counter(fail_res, res); > > - if (csize > PAGE_SIZE) /* change csize and retry */ > + if (csize == CHARGE_SIZE) /* retry without batching */ > return CHARGE_RETRY; > > if (!(gfp_mask & __GFP_WAIT)) > -- > 1.7.3.5 > > -- > 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 policy in Canada: sign http://dissolvethecrtc.ca/ > Don't email: email@kvack.org -- Gleb. -- 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 policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org