From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx176.postini.com [74.125.245.176]) by kanga.kvack.org (Postfix) with SMTP id 763916B002B for ; Fri, 10 Aug 2012 12:50:24 -0400 (EDT) Message-ID: <50253B95.7010905@jp.fujitsu.com> Date: Sat, 11 Aug 2012 01:49:25 +0900 From: Kamezawa Hiroyuki MIME-Version: 1.0 Subject: Re: [PATCH v2 02/11] memcg: Reclaim when more than one page needed. References: <1344517279-30646-1-git-send-email-glommer@parallels.com> <1344517279-30646-3-git-send-email-glommer@parallels.com> <20120810154240.GG1425@dhcp22.suse.cz> In-Reply-To: <20120810154240.GG1425@dhcp22.suse.cz> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Glauber Costa , linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, devel@openvz.org, Johannes Weiner , Andrew Morton , Christoph Lameter , David Rientjes , Pekka Enberg , Suleiman Souhlal (2012/08/11 0:42), Michal Hocko wrote: > On Thu 09-08-12 17:01:10, Glauber Costa wrote: > [...] >> @@ -2317,18 +2318,18 @@ static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, >> } else >> mem_over_limit = mem_cgroup_from_res_counter(fail_res, res); >> /* >> - * nr_pages can be either a huge page (HPAGE_PMD_NR), a batch >> - * of regular pages (CHARGE_BATCH), or a single regular page (1). >> - * >> * Never reclaim on behalf of optional batching, retry with a >> * single page instead. >> */ >> - if (nr_pages == CHARGE_BATCH) >> + if (nr_pages > min_pages) >> return CHARGE_RETRY; > > This is dangerous because THP charges will be retried now while they > previously failed with CHARGE_NOMEM which means that we will keep > attempting potentially endlessly. with THP, I thought nr_pages == min_pages, and no retry. > Why cannot we simply do if (nr_pages < CHARGE_BATCH) and get rid of the > min_pages altogether? Hm, I think a slab can be larger than CHARGE_BATCH. > Also the comment doesn't seem to be valid anymore. > I agree it's not clean. Because our assumption on nr_pages are changed, I think this behavior should not depend on nr_pages value.. Shouldn't we have a flag to indicate "trial-for-batched charge" ? Thanks, -Kame -- 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