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Date: Fri, 9 Jan 2009 13:47:36 +0900 From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> To: balbir@...ux.vnet.ibm.com Cc: Daisuke Nishimura <nishimura@....nes.nec.co.jp>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, lizf@...fujitsu.com, menage@...gle.com, "kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com> Subject: Re: [RFC][PATCH 1/4] memcg: fix for mem_cgroup_get_reclaim_stat_from_page On Fri, 9 Jan 2009 10:02:57 +0530 Balbir Singh <balbir@...ux.vnet.ibm.com> wrote: > > pc = lookup_page_cgroup(page); > > + smp_rmb(); > > Do you really need the read memory barrier? > Necessary. > > + if (!PageCgroupUsed(pc)) > > + return NULL; > > + > > In this case we've hit a case where the page is valid and the pc is > not. This does fix the problem, but won't this impact us getting > correct reclaim stats and thus indirectly impact the working of > pressure? > - If retruns NULL, only global LRU's status is updated. Because this page is not belongs to any memcg, we cannot update any counters. But yes, your point is a concern. Maybe moving acitvate_page() to == do_swap_page() { - activate_page() mem_cgroup_try_charge().. .... mem_cgroup_commit_charge().... .... + activate_page() } == is necessary. How do you think, kosaki ? Thanks, -Kame -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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