From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755815Ab1G2KGO (ORCPT ); Fri, 29 Jul 2011 06:06:14 -0400 Received: from cantor2.suse.de ([195.135.220.15]:55543 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755413Ab1G2KGN (ORCPT ); Fri, 29 Jul 2011 06:06:13 -0400 Date: Fri, 29 Jul 2011 11:06:09 +0100 From: Mel Gorman To: Keiichi KII Cc: "linux-kernel@vger.kernel.org" , Ingo Molnar , "linux-mm@kvack.org" , Tom Zanussi , "riel@redhat.com" , Steven Rostedt , Fr??d??ric Weisbecker , Wu Fengguang , "BA, Moussa" Subject: Re: [RFC PATCH -tip 4/5] tracepoints: add tracepoints for pagecache Message-ID: <20110729100609.GR3010@suse.de> References: <4E24A61D.4060702@bx.jp.nec.com> <4E24A7BB.1040800@bx.jp.nec.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <4E24A7BB.1040800@bx.jp.nec.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 18, 2011 at 05:38:03PM -0400, Keiichi KII wrote: > From: Keiichi Kii > > This patch adds several tracepoints to track pagecach behavior. > These trecepoints would help us monitor pagecache usage with high resolution. > There are a few spelling mistakes there but what harm. This is an RFC. Again, it would be really nice if the changelog explained why it was useful to monitor pagecache usage at this resolution. For example, I could identify files with high and low hit ratios and conceivably identify system activity that resulted in page cache being trashed. However, even in that case, I don't necessarily care which files got chucked out and that sort of problem can also be seen via fault rates. Another scenario that may be useful is it could potentially identify an application bug that was invalidating a portion of a file that was in fact hot and in use by other processes. I'm sure you have much better examples that motivated the development of this series :) The tracepoints themselves look fine. -- Mel Gorman SUSE Labs