linux-kernel - Re: [patch] mm, thp: abort compaction if migration page cannot be charged to memcg

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.00.1206251726040.1895@chino.kir.corp.google.com>
Date:	Mon, 25 Jun 2012 17:32:00 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Rik van Riel <riel@...hat.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Minchan Kim <minchan@...nel.org>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [patch] mm, thp: abort compaction if migration page cannot be
 charged to memcg

On Mon, 25 Jun 2012, Rik van Riel wrote:

> The patch makes sense, however I wonder if it would make
> more sense in the long run to allow migrate/compaction to
> temporarily exceed the memcg memory limit for a cgroup,
> because the original page will get freed again soon anyway.
> 
> That has the potential to improve compaction success, and
> reduce compaction related CPU use.
> 

Yeah, Kame brought up the same point with a sample patch by allowing the 
temporary charge for the new page.  It would certainly solve this problem 
in a way that we don't have to even touch compaction, it's disappointing 
that we have to charge memory to do a page migration.  I'm not so sure 
about the approach of temporarily allowing the excess charge, however, 
since it would scale with the number of cpus doing compaction or 
migration, which could end up with PAGE_SIZE * nr_cpu_ids.

I haven't looked at it (yet), but I'm hoping that there's a way to avoid 
charging the temporary page at all until after move_to_new_page() 
succeeds, i.e. find a way to uncharge page before charging newpage.  We 
currently don't charge things like vmalloc() memory to things that call 
alloc_pages() directly so it seems like it's plausible without causing 
usage > limit.
--
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/