From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with ESMTP id 3E4916B0218 for ; Tue, 18 May 2010 11:24:18 -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: <20100518151626.GA7748@Krystal> References: <20100514183242.GA11795@Krystal> <1273862945.1674.14.camel@laptop> <20100517224243.GA10603@Krystal> <1274185160.5605.7787.camel@twins> <20100518151626.GA7748@Krystal> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Date: Tue, 18 May 2010 17:23:53 +0200 Message-ID: <1274196233.5605.8169.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 Tue, 2010-05-18 at 11:16 -0400, Mathieu Desnoyers wrote: > > Also, suppose it was still in the page-cache and still dirty, a steal() > > would then punch a hole in the file. >=20 > page_cache_pipe_buf_steal starts by doing a wait_on_page_writeback(page);= and > then does a try_to_release_page(page, GFP_KERNEL). Only if that succeeds = is the > action of stealing succeeding.=20 If you're going to wait for writeback I don't really see the advantage of stealing over simply allocating a new page. -- 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