linux-kernel - Re: [PATCH 07/10] mm: vmscan: Block kswapd if it is encountering pages under writeback

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: <20130319105748.GH2055@suse.de>
Date:	Tue, 19 Mar 2013 10:57:48 +0000
From:	Mel Gorman <mgorman@...e.de>
To:	Simon Jeons <simon.jeons@...il.com>
Cc:	Linux-MM <linux-mm@...ck.org>, Jiri Slaby <jslaby@...e.cz>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Rik van Riel <riel@...hat.com>,
	Zlatko Calusic <zcalusic@...sync.net>,
	Johannes Weiner <hannes@...xchg.org>,
	dormando <dormando@...ia.net>,
	Satoru Moriya <satoru.moriya@....com>,
	Michal Hocko <mhocko@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/10] mm: vmscan: Block kswapd if it is encountering
 pages under writeback

On Mon, Mar 18, 2013 at 07:37:42PM +0800, Simon Jeons wrote:
> On 03/17/2013 09:04 PM, Mel Gorman wrote:
> >Historically, kswapd used to congestion_wait() at higher priorities if it
> >was not making forward progress. This made no sense as the failure to make
> >progress could be completely independent of IO. It was later replaced by
> >wait_iff_congested() and removed entirely by commit 258401a6 (mm: don't
> >wait on congested zones in balance_pgdat()) as it was duplicating logic
> >in shrink_inactive_list().
> >
> >This is problematic. If kswapd encounters many pages under writeback and
> >it continues to scan until it reaches the high watermark then it will
> >quickly skip over the pages under writeback and reclaim clean young
> >pages or push applications out to swap.
> >
> >The use of wait_iff_congested() is not suited to kswapd as it will only
> >stall if the underlying BDI is really congested or a direct reclaimer was
> >unable to write to the underlying BDI. kswapd bypasses the BDI congestion
> >as it sets PF_SWAPWRITE but even if this was taken into account then it
> 
> Where will check this flag?
> 

may_write_to_queue

-- 
Mel Gorman
SUSE Labs
--
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/