From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756196AbZBSOVu (ORCPT ); Thu, 19 Feb 2009 09:21:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752710AbZBSOVm (ORCPT ); Thu, 19 Feb 2009 09:21:42 -0500 Received: from g1t0026.austin.hp.com ([15.216.28.33]:14629 "EHLO g1t0026.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751844AbZBSOVl (ORCPT ); Thu, 19 Feb 2009 09:21:41 -0500 Subject: Re: [PATCH] Add tracepoints to track pagecache transition From: Lee Schermerhorn To: KOSAKI Motohiro Cc: Atsushi Tsuji , Peter Zijlstra , linux-kernel@vger.kernel.org, Jason Baron , Ingo Molnar , Mathieu Desnoyers , "Frank Ch. Eigler" , Kazuto Miyoshi , rostedt@goodmis.org, linux-mm , Andrew Morton , Nick Piggin , Hugh Dickins In-Reply-To: <2f11576a0902190512y1ac60b11s4927533977dc01e7@mail.gmail.com> References: <1234863220.4744.34.camel@laptop> <499A99BC.2080700@bk.jp.nec.com> <20090217201651.576E.A69D9226@jp.fujitsu.com> <499CE2FE.90503@bk.jp.nec.com> <2f11576a0902190512y1ac60b11s4927533977dc01e7@mail.gmail.com> Content-Type: text/plain Organization: HP/OSLO Date: Thu, 19 Feb 2009 09:21:31 -0500 Message-Id: <1235053291.8424.14.camel@lts-notebook> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2009-02-19 at 22:12 +0900, KOSAKI Motohiro wrote: > > Hi Kosaki-san, > > > > Thank you for your comment. > > > > KOSAKI Motohiro wrote: > >> Hi > >> > >> > >> In my 1st impression, this patch description is a bit strange. > >> > >>> The below patch adds instrumentation for pagecache. > >>> > >>> I thought it would be useful to trace pagecache behavior for problem > >>> analysis (performance bottlenecks, behavior differences between stable > >>> time and trouble time). > >>> > >>> By using those tracepoints, we can describe and visualize pagecache > >>> transition (file-by-file basis) in kernel and pagecache > >>> consumes most of the memory in running system and pagecache hit rate > >>> and writeback behavior will influence system load and performance. > >> > >> Why do you think this tracepoint describe pagecache hit rate? > >> and, why describe writeback behavior? > > > > I mean, we can describe file-by-file basis pagecache usage by using > > these tracepoints and it is important for analyzing process I/O behavior. > > More confusing. > Your page cache tracepoint don't have any per-process information. > > > > Currently, we can understand the amount of pagecache from "Cached" > > in /proc/meminfo. So I'd like to understand which files are using pagecache. > > There is one meta question, Why do you think file-by-file pagecache > infomartion is valueable? > One might take a look at Marcello Tosatti's old 'vmtrace' patch. It contains it's own data store/transport via relayfs, but the trace points could be ported to the current kernel tracing infrastructure. Here's a starting point: http://linux-mm.org/VmTrace Quoting from that page: >>From the previous email to linux-mm: >"The sequence of pages which a given process or workload accesses >during its lifetime, a.k.a. "reference trace", is very important >information. It has been used in the past for comparison of page >replacement algorithms and other optimizations..." Lee