linux-kernel - Re: [PATCH for 3.2.34] memcg: do not trigger OOM from add_to_page_cache

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Message-ID: <20121206170658.GD10931@dhcp22.suse.cz>
Date:	Thu, 6 Dec 2012 18:06:58 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	azurIt <azurit@...ox.sk>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	cgroups mailinglist <cgroups@...r.kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH for 3.2.34] memcg: do not trigger OOM from
 add_to_page_cache_locked

On Thu 06-12-12 11:12:49, azurIt wrote:
> >Dohh. The very same stack mem_cgroup_newpage_charge called from the page
> >fault. The heavy inlining is not particularly helping here... So there
> >must be some other THP charge leaking out.
> >[/me is diving into the code again]
> >
> >* do_huge_pmd_anonymous_page falls back to handle_pte_fault
> >* do_huge_pmd_wp_page_fallback falls back to simple pages so it doesn't
> >  charge the huge page
> >* do_huge_pmd_wp_page splits the huge page and retries with fallback to
> >  handle_pte_fault
> >* collapse_huge_page is not called in the page fault path
> >* do_wp_page, do_anonymous_page and __do_fault  operate on a single page
> >  so the memcg charging cannot return ENOMEM
> >
> >There are no other callers AFAICS so I am getting clueless. Maybe more
> >debugging will tell us something (the inlining has been reduced for thp
> >paths which can reduce performance in thp page fault heavy workloads but
> >this will give us better traces - I hope).
> 
> 
> Should i apply all patches togather? (fix for this bug, more log
> messages, backported fix from 3.5 and this new one)

Yes please
-- 
Michal Hocko
SUSE Labs
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