From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752975Ab0ESPfm (ORCPT ); Wed, 19 May 2010 11:35:42 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:39271 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752237Ab0ESPfl (ORCPT ); Wed, 19 May 2010 11:35:41 -0400 Date: Wed, 19 May 2010 08:32:15 -0700 (PDT) From: Linus Torvalds To: Miklos Szeredi cc: npiggin@suse.de, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, peterz@infradead.org, fweisbec@gmail.com, tardyp@gmail.com, mingo@elte.hu, acme@redhat.com, tzanussi@gmail.com, paulus@samba.org, linux-kernel@vger.kernel.org, arjan@infradead.org, ziga.mahkovec@gmail.com, davem@davemloft.net, linux-mm@kvack.org, akpm@linux-foundation.org, kosaki.motohiro@jp.fujitsu.com, cl@linux-foundation.org, tj@kernel.org, jens.axboe@oracle.com Subject: Re: Unexpected splice "always copy" behavior observed In-Reply-To: Message-ID: References: <20100518153440.GB7748@Krystal> <1274197993.26328.755.camel@gandalf.stny.rr.com> <1274199039.26328.758.camel@gandalf.stny.rr.com> <20100519063116.GR2516@laptop> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 19 May 2010, Miklos Szeredi wrote: > > Another limitation I found while splicing from one file to another is > that stealing from the source file's page cache does not always > succeed. This turned out to be because of a reference from the lru > cache for freshly read pages. I'm not sure how this could be fixed. It should be fixed by saying "you can't always just move the page". Copying is not evil. Complexity to avoid copies is evil. Linus