From: Michal Hocko <mhocko@kernel.org>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Minchan Kim <minchan@kernel.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Mel Gorman <mgorman@techsingularity.net>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch v2] mm, vmscan: avoid thrashing anon lru when free + file is low
Date: Tue, 2 May 2017 10:02:47 +0200 [thread overview]
Message-ID: <20170502080246.GD14593@dhcp22.suse.cz> (raw)
In-Reply-To: <alpine.DEB.2.10.1705011432220.137835@chino.kir.corp.google.com>
On Mon 01-05-17 14:34:21, David Rientjes wrote:
[...]
> @@ -2204,8 +2204,17 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
> }
>
> if (unlikely(pgdatfile + pgdatfree <= total_high_wmark)) {
> - scan_balance = SCAN_ANON;
> - goto out;
> + /*
> + * Force SCAN_ANON if there are enough inactive
> + * anonymous pages on the LRU in eligible zones.
> + * Otherwise, the small LRU gets thrashed.
> + */
> + if (!inactive_list_is_low(lruvec, false, sc, false) &&
> + lruvec_lru_size(lruvec, LRU_INACTIVE_ANON, sc->reclaim_idx)
> + >> sc->priority) {
> + scan_balance = SCAN_ANON;
> + goto out;
> + }
I have already asked and my questions were ignored. So let me ask again
and hopefuly not get ignored this time. So Why do we need a different
criterion on anon pages than file pages? I do agree that blindly
scanning anon pages when file pages are low is very suboptimal but this
adds yet another heuristic without _any_ numbers. Why cannot we simply
treat anon and file pages equally? Something like the following
if (pgdatfile + pgdatanon + pgdatfree > 2*total_high_wmark) {
scan_balance = SCAN_FILE;
if (pgdatfile < pgdatanon)
scan_balance = SCAN_ANON;
goto out;
}
Also it would help to describe the workload which can trigger this
behavior so that we can compare numbers before and after this patch.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2017-05-02 8:03 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 [this message]
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 ` [patch] " Michal Hocko
2017-04-18 7:11 ` Michal Hocko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170502080246.GD14593@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=hannes@cmpxchg.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@techsingularity.net \
--cc=minchan@kernel.org \
--cc=rientjes@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).