From: Michal Hocko <mhocko@suse.cz>
To: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Satoru Moriya <satoru.moriya@hds.com>,
Mel Gorman <mgorman@suse.de>,
Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [patch 2/8] mm: vmscan: disregard swappiness shortly before going OOM
Date: Fri, 14 Dec 2012 17:13:45 +0100 [thread overview]
Message-ID: <20121214161345.GA18780@dhcp22.suse.cz> (raw)
In-Reply-To: <50CB493B.8000900@redhat.com>
On Fri 14-12-12 10:43:55, Rik van Riel wrote:
> 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.
Yes, but this is the global reclaim path. I was arguing about
swappiness==0 & memcg. As this patch doesn't make a big difference for
the global case (as both the changelog and you mentioned) then we should
focus on whether this is desirable change for the memcg path. I think it
makes sense to keep "no swapping at all for memcg semantic" as we have
it currently.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2012-12-14 16:13 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-12 21:43 [patch 0/8] page reclaim bits Johannes Weiner
2012-12-12 21:43 ` [patch 1/8] mm: memcg: only evict file pages when we have plenty Johannes Weiner
2012-12-12 21:53 ` Rik van Riel
2012-12-12 22:28 ` Johannes Weiner
2012-12-13 10:07 ` Mel Gorman
2012-12-13 14:44 ` Mel Gorman
2012-12-13 14:55 ` Michal Hocko
2012-12-16 1:21 ` Simon Jeons
2012-12-17 15:54 ` Michal Hocko
2012-12-19 5:21 ` Simon Jeons
2012-12-19 9:20 ` Mel Gorman
2012-12-13 5:36 ` Simon Jeons
2012-12-13 5:34 ` Simon Jeons
2012-12-12 21:43 ` [patch 2/8] mm: vmscan: disregard swappiness shortly before going OOM Johannes Weiner
2012-12-12 22:01 ` Rik van Riel
2012-12-13 5:56 ` Simon Jeons
2012-12-13 10:34 ` Mel Gorman
2012-12-13 15:29 ` Michal Hocko
2012-12-13 16:05 ` Michal Hocko
2012-12-13 22:25 ` Satoru Moriya
2012-12-14 4:50 ` Johannes Weiner
2012-12-14 8:37 ` Michal Hocko
2012-12-14 15:43 ` Rik van Riel
2012-12-14 16:13 ` Michal Hocko [this message]
2012-12-15 0:18 ` Johannes Weiner
2012-12-17 16:37 ` Michal Hocko
2012-12-17 17:54 ` Johannes Weiner
2012-12-17 19:58 ` Michal Hocko
2012-12-14 20:17 ` Satoru Moriya
2012-12-14 19:44 ` Satoru Moriya
2012-12-13 19:05 ` Johannes Weiner
2012-12-13 19:47 ` Mel Gorman
2012-12-12 21:43 ` [patch 3/8] mm: vmscan: save work scanning (almost) empty LRU lists Johannes Weiner
2012-12-12 22:02 ` Rik van Riel
2012-12-13 10:41 ` Mel Gorman
2012-12-13 19:33 ` Johannes Weiner
2012-12-13 15:43 ` Michal Hocko
2012-12-13 19:38 ` Johannes Weiner
2012-12-14 8:46 ` Michal Hocko
2012-12-12 21:43 ` [patch 4/8] mm: vmscan: clarify LRU balancing close to OOM Johannes Weiner
2012-12-12 22:03 ` Rik van Riel
2012-12-13 10:46 ` Mel Gorman
2012-12-12 21:43 ` [patch 5/8] mm: vmscan: improve comment on low-page cache handling Johannes Weiner
2012-12-12 22:04 ` Rik van Riel
2012-12-13 10:47 ` Mel Gorman
2012-12-13 16:07 ` Michal Hocko
2012-12-12 21:43 ` [patch 6/8] mm: vmscan: clean up get_scan_count() Johannes Weiner
2012-12-12 22:06 ` Rik van Riel
2012-12-13 11:07 ` Mel Gorman
2012-12-13 16:18 ` Michal Hocko
2012-12-12 21:43 ` [patch 7/8] mm: vmscan: compaction works against zones, not lruvecs Johannes Weiner
2012-12-12 22:31 ` Rik van Riel
2012-12-13 11:12 ` Mel Gorman
2012-12-13 16:48 ` Michal Hocko
2012-12-12 21:43 ` [patch 8/8] mm: reduce rmap overhead for ex-KSM page copies created on swap faults Johannes Weiner
2012-12-12 22:34 ` Rik van Riel
2012-12-12 21:50 ` [patch 0/8] page reclaim bits Andrew Morton
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