From: Michal Hocko <mhocko@kernel.org>
To: David Rientjes <rientjes@google.com>
Cc: Minchan Kim <minchan@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Mel Gorman <mgorman@techsingularity.net>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch] mm, vmscan: avoid thrashing anon lru when free + file is low
Date: Wed, 19 Apr 2017 09:04:25 +0200 [thread overview]
Message-ID: <20170419070424.GA28263@dhcp22.suse.cz> (raw)
In-Reply-To: <alpine.DEB.2.10.1704181402510.112481@chino.kir.corp.google.com>
On Tue 18-04-17 14:32:56, David Rientjes wrote:
[...]
> If the suggestion is checking
> NR_ACTIVE_ANON + NR_INACTIVE_ANON > total_high_wmark pages, it would be a
> separate heurstic to address a problem that I'm not having :) My issue is
> specifically when NR_ACTIVE_FILE + NR_INACTIVE_FILE < total_high_wmark,
> NR_ACTIVE_ANON + NR_INACTIVE_ANON is very large, but all not on this
> lruvec's evictable lrus.
Hmm, why are those pages not moved to the unevictable LRU lists?
> This is the reason why I chose lruvec_lru_size() rather than per-node
> statistics. The argument could also be made for the file lrus in the
> get_scan_count() heuristic that forces SCAN_ANON, but I have not met such
> an issue (yet). I could follow-up with that change or incorporate it into
> a v2 of this patch if you'd prefer.
>
> In other words, I want get_scan_count() to not force SCAN_ANON and
> fallback to SCAN_FRACT, absent other heuristics, if the amount of
> evictable anon is below a certain threshold for this lruvec. I
> arbitrarily chose SWAP_CLUSTER_MAX to be conservative, but I could easily
> compare to total_high_wmark as well, although I would consider that more
> aggressive.
>
> So we're in global reclaim, our file lrus are below thresholds, but we
> don't want to force SCAN_ANON for all lruvecs if there's not enough to
> reclaim from evictable anon. Do you have a suggestion for how to
> implement this logic other than this patch?
I agree that forcing SCAN_ANON without looking at the ANON lru size is
not optimal but I would rather see the same criterion for both anon and
file. get_scan_count is full of magic heuristics which tend to break for
different workloads. Let's not add another magic on top please.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2017-04-19 7:04 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-18 0:06 [patch] mm, vmscan: avoid thrashing anon lru when free + file is low David Rientjes
2017-04-18 1:36 ` Minchan Kim
2017-04-18 21:32 ` David Rientjes
2017-04-19 0:14 ` Minchan Kim
2017-04-19 23:24 ` David Rientjes
2017-04-20 6:09 ` Minchan Kim
2017-05-01 21:34 ` [patch v2] " David Rientjes
2017-05-02 8:02 ` Michal Hocko
2017-05-02 20:41 ` David Rientjes
2017-05-03 6:15 ` Michal Hocko
2017-05-03 7:06 ` Michal Hocko
2017-05-03 8:49 ` Michal Hocko
2017-05-03 22:52 ` David Rientjes
2017-05-04 11:43 ` Michal Hocko
2017-05-31 15:20 ` Michal Hocko
2017-06-02 20:36 ` Andrew Morton
2017-06-04 22:27 ` David Rientjes
2017-04-19 7:04 ` Michal Hocko [this message]
2017-04-18 7:11 ` [patch] " Michal Hocko
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