linux-kernel - Re: [patch 2/8] mm: vmscan: disregard swappiness shortly before going OOM

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: <50CB493B.8000900@redhat.com>
Date:	Fri, 14 Dec 2012 10:43:55 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Michal Hocko <mhocko@...e.cz>
CC:	Johannes Weiner <hannes@...xchg.org>,
	Satoru Moriya <satoru.moriya@....com>,
	Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [patch 2/8] mm: vmscan: disregard swappiness shortly before going
 OOM

On 12/14/2012 03:37 AM, Michal Hocko wrote:

> I can answer the later. Because memsw comes with its price and
> swappiness is much cheaper. On the other hand it makes sense that
> swappiness==0 doesn't swap at all. Or do you think we should get back to
> _almost_ doesn't swap at all?

swappiness==0 will swap in emergencies, specifically when we have
almost no page cache left, we will still swap things out:

         if (global_reclaim(sc)) {
                 free  = zone_page_state(zone, NR_FREE_PAGES);
                 if (unlikely(file + free <= high_wmark_pages(zone))) {
                         /*
                          * If we have very few page cache pages, force-scan
                          * anon pages.
                          */
                         fraction[0] = 1;
                         fraction[1] = 0;
                         denominator = 1;
                         goto out;

This makes sense, because people who set swappiness==0 but
do have swap space available would probably prefer some
emergency swapping over an OOM kill.

-- 
All rights reversed
--
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/