From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754262Ab3KNP5V (ORCPT ); Thu, 14 Nov 2013 10:57:21 -0500 Received: from mx1.redhat.com ([209.132.183.28]:30917 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754060Ab3KNP5L (ORCPT ); Thu, 14 Nov 2013 10:57:11 -0500 Message-ID: <5284F2B0.1080708@redhat.com> Date: Thu, 14 Nov 2013 10:56:32 -0500 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: Vlastimil Babka CC: Johannes Weiner , Andrew Morton , Andi Kleen , Andrea Arcangeli , Greg Thelen , Christoph Hellwig , Hugh Dickins , Jan Kara , KOSAKI Motohiro , Mel Gorman , Minchan Kim , Peter Zijlstra , Michel Lespinasse , Seth Jennings , Roman Gushchin , Ozgun Erdogan , Metin Doslu , Tejun Heo , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [patch 0/8] mm: thrash detection-based file cache sizing v5 References: <1381441622-26215-1-git-send-email-hannes@cmpxchg.org> <5264F353.1080603@suse.cz> In-Reply-To: <5264F353.1080603@suse.cz> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/21/2013 05:26 AM, Vlastimil Babka wrote: > On 10/10/2013 11:46 PM, Johannes Weiner wrote: >> Hi everyone, >> >> here is an update to the cache sizing patches for 3.13. >> >> Changes in this revision >> >> o Drop frequency synchronization between refaulted and demoted pages >> and just straight up activate refaulting pages whose access >> frequency indicates they could stay in memory. This was suggested >> by Rik van Riel a looong time ago but misinterpretation of test >> results during early stages of development took me a while to >> overcome. It's still the same overall concept, but a little simpler >> and with even faster cache adaptation. Yay! > > Oh, I liked the previous approach with direct competition between the > refaulted and demoted page :) Doesn't the new approach favor the > refaulted page too much? No wonder it leads to faster cache adaptation, > but could it also cause degradations for workloads that don't benefit > from it? Were there any tests for performance regressions on workloads > that were not the target of the patchset? This is a good question, and one that is probably best settled through experimentation. Even with the first scheme (fault refaulted page to the inactive list), those pages only need 2 accesses to be promoted to the active list. That is because a refault tends to immediately be followed by an access (after all, the attempted access causes the page to get loaded back into memory).