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 40FB66B021A for ; Tue, 18 May 2010 08:19:49 -0400 (EDT) Subject: Re: [RFC] Tracer Ring Buffer splice() vs page cache [was: Re: Perf and ftrace [was Re: PyTimechart]] From: Peter Zijlstra In-Reply-To: <20100517224243.GA10603@Krystal> References: <20100514183242.GA11795@Krystal> <1273862945.1674.14.camel@laptop> <20100517224243.GA10603@Krystal> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Date: Tue, 18 May 2010 14:19:20 +0200 Message-ID: <1274185160.5605.7787.camel@twins> Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org To: Mathieu Desnoyers Cc: Steven Rostedt , Frederic Weisbecker , Pierre Tardy , Ingo Molnar , Arnaldo Carvalho de Melo , Tom Zanussi , Paul Mackerras , linux-kernel@vger.kernel.org, arjan@infradead.org, ziga.mahkovec@gmail.com, davem , linux-mm@kvack.org, Andrew Morton , KOSAKI Motohiro , Christoph Lameter , Tejun Heo , Jens Axboe List-ID: On Mon, 2010-05-17 at 18:42 -0400, Mathieu Desnoyers wrote: > I'll continue to look into this. One of the things I noticed that that we= could > possibly use the "steal()" operation to steal the pages back from the pag= e cache > to repopulate the ring buffer rather than continuously allocating new pag= es. If > steal() fails for some reasons, then we can fall back on page allocation.= I'm > not sure it is safe to assume anything about pages being in the page cach= e > though.=20 Also, suppose it was still in the page-cache and still dirty, a steal() would then punch a hole in the file. > Maybe the safest route is to just allocate new pages for now. Yes, that seems to be the only sane approach. -- 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