linux-kernel - Re: [PATCH 5/6] mm, compaction: skip compound pages by order in free scanner

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: <20150616054505.GE12641@js1304-P5Q-DELUXE>
Date:	Tue, 16 Jun 2015 14:45:06 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Minchan Kim <minchan@...nel.org>,
	Mel Gorman <mgorman@...e.de>,
	Michal Nazarewicz <mina86@...a86.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Christoph Lameter <cl@...ux.com>,
	Rik van Riel <riel@...hat.com>,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH 5/6] mm, compaction: skip compound pages by order in free
 scanner

On Wed, Jun 10, 2015 at 11:32:33AM +0200, Vlastimil Babka wrote:
> The compaction free scanner is looking for PageBuddy() pages and skipping all
> others.  For large compound pages such as THP or hugetlbfs, we can save a lot
> of iterations if we skip them at once using their compound_order(). This is
> generally unsafe and we can read a bogus value of order due to a race, but if
> we are careful, the only danger is skipping too much.
> 
> When tested with stress-highalloc from mmtests on 4GB system with 1GB hugetlbfs
> pages, the vmstat compact_free_scanned count decreased by at least 15%.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>


Acked-by: Joonsoo Kim <iamjoonsoo.kim@....com>

Thanks.
--
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/