From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id D85346B003D for ; Thu, 19 Feb 2009 09:21:41 -0500 (EST) Subject: Re: [PATCH] Add tracepoints to track pagecache transition From: Lee Schermerhorn 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 Date: Thu, 19 Feb 2009 09:21:31 -0500 Message-Id: <1235053291.8424.14.camel@lts-notebook> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org 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 List-ID: 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 -- 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