From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755968Ab0ICIHQ (ORCPT ); Fri, 3 Sep 2010 04:07:16 -0400 Received: from smtp.nokia.com ([192.100.122.230]:50924 "EHLO mgw-mx03.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755482Ab0ICIHG (ORCPT ); Fri, 3 Sep 2010 04:07:06 -0400 Date: Fri, 3 Sep 2010 11:06:42 +0300 From: Pauli Nieminen To: ext Peter Zijlstra Cc: ext Mathieu Desnoyers , Tony Lindgren , Jarkko Nikula , "linux-kernel@vger.kernel.org" , Pauli Subject: Re: IPC between application and xserver is causing extra context switches Message-ID: <20100903080642.GB19353@squeeze> References: <20100809150211.GA29771@burn-it> <20100901025817.GA6200@Krystal> <20100903071738.GA19353@squeeze> <1283499074.1783.59.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1283499074.1783.59.camel@laptop> User-Agent: Mutt/1.5.20 (2009-06-14) X-OriginalArrivalTime: 03 Sep 2010 08:06:46.0235 (UTC) FILETIME=[F3E88AB0:01CB4B3E] X-Nokia-AV: Clean Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/09/10 09:31 +0200, ext Peter Zijlstra wrote: > On Fri, 2010-09-03 at 10:17 +0300, Pauli Nieminen wrote: > > Scheduling at write is wrong because xserver doesn't know about client > > priorities. > > Waking up the client at write is correct because you don't know if there > is more to be written. > > Really, your assumptions about when things schedule is wrong. > > Where is it wrong? I'm just explaining what I have seen in trace output. I also try to explain why it is wrong for xserver/client communication. If problems that I see aren't scheduling problems then xserver has to understand client priorities and duplicate scheduler code in user space.