From: Mel Gorman <mgorman@techsingularity.net>
To: Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@suse.cz>, Vlastimil Babka <vbabka@suse.cz>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/5] mm, vmscan: Do not account skipped pages as scanned
Date: Mon, 25 Jul 2016 10:20:14 +0100 [thread overview]
Message-ID: <20160725092014.GL10438@techsingularity.net> (raw)
In-Reply-To: <20160725080456.GB1660@bbox>
On Mon, Jul 25, 2016 at 05:04:56PM +0900, Minchan Kim wrote:
> > @@ -1429,6 +1429,9 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> > continue;
> > }
> >
> > + /* Pages skipped do not contribute to scan */
> > + scan++;
> > +
>
> As I mentioned in previous version, under irq-disabled-spin-lock, such
> unbounded operation would make the latency spike worse if there are
> lot of pages we should skip.
>
> Don't we take care it?
It's not unbounded, it's bound by the size of the LRU list and it's not
going to be enough to trigger a warning. While the lock hold time may be
undesirable, unlocking it every SWAP_CLUSTER_MAX pages may increase overall
contention. There also is the question of whether skipped pages should be
temporarily putback before unlocking the LRU to avoid isolated pages being
unavailable for too long. It also cannot easily just return early without
prematurely triggering OOM due to a lack of progress. I didn't feel the
complexity was justified.
--
Mel Gorman
SUSE Labs
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next prev parent reply other threads:[~2016-07-25 9:20 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-20 15:21 [PATCH 0/5] Candidate fixes for premature OOM kills with node-lru v1 Mel Gorman
2016-07-20 15:21 ` [PATCH 1/5] mm, vmscan: Do not account skipped pages as scanned Mel Gorman
2016-07-21 5:16 ` Minchan Kim
2016-07-21 8:15 ` Mel Gorman
2016-07-21 8:31 ` Minchan Kim
2016-07-25 8:04 ` Minchan Kim
2016-07-25 9:20 ` Mel Gorman [this message]
2016-07-28 1:38 ` Minchan Kim
2016-07-20 15:21 ` [PATCH 2/5] mm: add per-zone lru list stat Mel Gorman
2016-07-21 7:10 ` Joonsoo Kim
2016-07-23 0:45 ` Fengguang Wu
2016-07-23 1:25 ` Minchan Kim
2016-07-20 15:21 ` [PATCH 3/5] mm, vmscan: Remove highmem_file_pages Mel Gorman
2016-07-20 15:21 ` [PATCH 4/5] mm: Remove reclaim and compaction retry approximations Mel Gorman
2016-07-20 15:21 ` [PATCH 5/5] mm: consider per-zone inactive ratio to deactivate Mel Gorman
2016-07-21 5:30 ` Minchan Kim
2016-07-21 8:08 ` Mel Gorman
2016-07-21 7:10 ` Joonsoo Kim
2016-07-21 8:16 ` Mel Gorman
2016-07-21 7:07 ` [PATCH 0/5] Candidate fixes for premature OOM kills with node-lru v1 Minchan Kim
2016-07-21 9:15 ` Mel Gorman
2016-07-21 7:31 ` Joonsoo Kim
2016-07-21 8:39 ` Minchan Kim
2016-07-21 9:16 ` Mel Gorman
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