From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 611DA6B003D for ; Thu, 30 Apr 2009 23:09:31 -0400 (EDT) Date: Thu, 30 Apr 2009 20:09:16 -0700 From: Elladan Subject: Re: [PATCH] vmscan: evict use-once pages first (v2) Message-ID: <20090501030916.GA25905@eskimo.com> References: <20090428044426.GA5035@eskimo.com> <20090428192907.556f3a34@bree.surriel.com> <1240987349.4512.18.camel@laptop> <20090429114708.66114c03@cuia.bos.redhat.com> <20090430072057.GA4663@eskimo.com> <20090430174536.d0f438dd.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090430174536.d0f438dd.akpm@linux-foundation.org> Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: Elladan , riel@redhat.com, peterz@infradead.org, linux-kernel@vger.kernel.org, tytso@mit.edu, kosaki.motohiro@jp.fujitsu.com, linux-mm@kvack.org List-ID: On Thu, Apr 30, 2009 at 05:45:36PM -0700, Andrew Morton wrote: > On Thu, 30 Apr 2009 00:20:58 -0700 > Elladan wrote: > > > > Elladan, does this smaller patch still work as expected? > > > > Rik, since the third patch doesn't work on 2.6.28 (without disabling a lot of > > code), I went ahead and tested this patch. > > > > The system does seem relatively responsive with this patch for the most part, > > with occasional lag. I don't see much evidence at least over the course of a > > few minutes that it pages out applications significantly. It seems about > > equivalent to the first patch. > > > > Given Andrew Morton's request that I track the Mapped: field in /proc/meminfo, > > I went ahead and did that with this patch built into a kernel. Compared to the > > standard Ubuntu kernel, this patch keeps significantly more Mapped memory > > around, and it shrinks at a slower rate after the test runs for a while. > > Eventually, it seems to reach a steady state. > > > > For example, with your patch, Mapped will often go for 30 seconds without > > changing significantly. Without your patch, it continuously lost about > > 500-1000K every 5 seconds, and then jumped up again significantly when I > > touched Firefox or other applications. I do see some of that behavior with > > your patch too, but it's much less significant. > > Were you able to tell whether altering /proc/sys/vm/swappiness appropriately > regulated the rate at which the mapped page count decreased? I don't believe so. I tested with swappiness=0 and =60, and in each case the mapped pages continued to decrease. I don't know at what rate though. If you'd like more precise data, I can rerun the test with appropriate logging. I admit my "Hey, latency is terrible and mapped pages is decreasing" testing is somewhat unscientific. I get the impression that VM regressions happen fairly regularly. Does anyone have good unit tests for this? Is seems like a difficult problem, since it's partly based on pattern and partly timing. -J -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org