From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753427Ab0ESQEy (ORCPT ); Wed, 19 May 2010 12:04:54 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:38979 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751453Ab0ESQEx (ORCPT ); Wed, 19 May 2010 12:04:53 -0400 Date: Wed, 19 May 2010 09:01:14 -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: > > And predictability is good. The thing I don't like about the above is > that it makes it totally unpredictable which pages will get moved, if > any. Tough. Think of it this way: it is predictable. They get predictably moved when moving is cheap and easy. It's about _performance_. Do you know when TLB misses happen? They are unpredictable. Do you know when the OS sends IPI's around? Do you know when scheduling happens? No you don't. So stop whining. Linus