From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262245AbVAIEHz (ORCPT ); Sat, 8 Jan 2005 23:07:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262246AbVAIEHz (ORCPT ); Sat, 8 Jan 2005 23:07:55 -0500 Received: from fw.osdl.org ([65.172.181.6]:36074 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S262245AbVAIEHu (ORCPT ); Sat, 8 Jan 2005 23:07:50 -0500 Date: Sat, 8 Jan 2005 20:07:34 -0800 (PST) From: Linus Torvalds To: Lee Revell cc: Chris Friesen , Mike Waychison , Alan Cox , Oleg Nesterov , William Lee Irwin III , Linux Kernel Mailing List Subject: Re: Make pipe data structure be a circular list of pages, rather than In-Reply-To: Message-ID: References: <41DE9D10.B33ED5E4@tv-sign.ru> <1105113998.24187.361.camel@localhost.localdomain> <41DEF81B.60905@sun.com> <41DF1F3D.3030006@nortelnetworks.com> <1105220326.24592.98.camel@krustophenia.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 8 Jan 2005, Linus Torvalds wrote: > > Short and sweet: the latency changes are in the noise for SMP, but can be > seen on UP. I'll look at it a bit more: since I had to add the coalescing > code anyway, I might also decide to re-use a buffer page rather than free > it immediately, since that may help latency for small writes. Side note: the SMP numbers seem to fluctuate wildly making any benchmarking a bit suspect. They probably depend very much on just how things get scheduled, and on inter-CPU cache behaviour. In contrast, the UP numbers are a lot more reliable, so I'll try to make sure that everything looks good on UP - which definitely means that I'll work to make sure that latency looks good too. Linus