From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta12.messagelabs.com (mail6.bemta12.messagelabs.com [216.82.250.247]) by kanga.kvack.org (Postfix) with ESMTP id F3EBC6B0169 for ; Mon, 8 Aug 2011 08:40:57 -0400 (EDT) Received: by vwm42 with SMTP id 42so3298669vwm.14 for ; Mon, 08 Aug 2011 05:40:55 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <4E3FD403.6000400@parallels.com> References: <20110808110658.31053.55013.stgit@localhost6> <4E3FD403.6000400@parallels.com> Date: Mon, 8 Aug 2011 15:40:55 +0300 Message-ID: Subject: Re: [PATCH 1/2] vmscan: promote shared file mapped pages From: Pekka Enberg Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Konstantin Khlebnikov Cc: "linux-mm@kvack.org" , Andrew Morton , "linux-kernel@vger.kernel.org" , Wu Fengguang , KAMEZAWA Hiroyuki , Johannes Weiner On Mon, Aug 8, 2011 at 3:18 PM, Konstantin Khlebnikov wrote: > Pekka Enberg wrote: >> >> Hi Konstantin, >> >> On Mon, Aug 8, 2011 at 2:06 PM, Konstantin Khlebnikov >> =A0wrote: >>> >>> Commit v2.6.33-5448-g6457474 (vmscan: detect mapped file pages used onl= y >>> once) >>> greatly decreases lifetime of single-used mapped file pages. >>> Unfortunately it also decreases life time of all shared mapped file >>> pages. >>> Because after commit v2.6.28-6130-gbf3f3bc (mm: don't mark_page_accesse= d >>> in fault path) >>> page-fault handler does not mark page active or even referenced. >>> >>> Thus page_check_references() activates file page only if it was used >>> twice while >>> it stays in inactive list, meanwhile it activates anon pages after firs= t >>> access. >>> Inactive list can be small enough, this way reclaimer can accidentally >>> throw away any widely used page if it wasn't used twice in short period= . >>> >>> After this patch page_check_references() also activate file mapped page >>> at first >>> inactive list scan if this page is already used multiple times via >>> several ptes. >>> >>> Signed-off-by: Konstantin Khlebnikov >> >> Both patches seem reasonable but the changelogs don't really explain >> why you're doing the changes. How did you find out about the problem? >> Is there some workload that's affected? How did you test your changes? >> > > I found this while trying to fix degragation in rhel6 (~2.6.32) from rhel= 5 > (~2.6.18). > There a complete mess with >100 web/mail/spam/ftp containers, > they share all their files but there a lot of anonymous pages: > ~500mb shared file mapped memory and 15-20Gb non-shared anonymous memory. > In this situation major-pagefaults are very costly, because all container= s > share the same page. > In my load kernel created a disproportionate pressure on the file memory, > compared with the anonymous, > they equaled only if I raise swappiness up to 150 =3D) > > These patches actually wasn't helped a lot in my problem, > but I saw noticable (10-20 times) reduce in count and average time of > major-pagefault in file-mapped areas. > > Actually both patches are fixes for commit v2.6.33-5448-g6457474, > because it was aimed at one scenario (singly used pages), > but it breaks the logic in other scenarios (shared and/or executable page= s) It'd be nice to have such details in the changelogs. FWIW, Acked-by: Pekka Enberg -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org