linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
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: Wed, 3 May 2017 09:06:56 +0200	[thread overview]
Message-ID: <20170503070656.GA8836@dhcp22.suse.cz> (raw)
In-Reply-To: <20170503061528.GB1236@dhcp22.suse.cz>

On Wed 03-05-17 08:15:28, Michal Hocko wrote:
> On Tue 02-05-17 13:41:23, David Rientjes wrote:
> > On Tue, 2 May 2017, Michal Hocko wrote:
[...]
> > > 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;
> > > 	}
> > > 
> > 
> > This would be substantially worse than the current code because it 
> > thrashes the anon lru when anon out numbers file pages rather than at the 
> > point we fall under the high watermarks for all eligible zones.  If you 
> > tested your suggestion, you could see gigabytes of memory left untouched 
> > on the file lru.  Anonymous memory is more probable to be part of the 
> > working set.
> 
> This was supposed to be more an example of a direction I was thinking,
> definitely not a final patch. I will think more to come up with a
> more complete proposal.

This is still untested but should be much closer to what I've had in
mind.
---
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 24efcc20af91..bcdad30f942d 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2174,8 +2174,14 @@ 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;
+			unsigned long pgdatanon;
+
+			pgdatanon = node_page_state(pgdat, NR_ACTIVE_ANON) +
+				node_page_state(pgdat, NR_INACTIVE_ANON);
+			if (pgdatanon + pgdatfree > total_high_wmark) {
+				scan_balance = SCAN_ANON;
+				goto out;
+			}
 		}
 	}
 

-- 
Michal Hocko
SUSE Labs

  reply	other threads:[~2017-05-03  7:07 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-18  0:06 [patch] " 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 [this message]
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=20170503070656.GA8836@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 \
    --subject='Re: [patch v2] mm, vmscan: avoid thrashing anon lru when free + file is low' \
    /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

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).