Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754652AbXFDRdI (ORCPT ); Mon, 4 Jun 2007 13:33:08 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750795AbXFDRcy (ORCPT ); Mon, 4 Jun 2007 13:32:54 -0400 Received: from www.osadl.org ([213.239.205.134]:51954 "EHLO mail.tglx.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750793AbXFDRcw (ORCPT ); Mon, 4 Jun 2007 13:32:52 -0400 Subject: Re: iperf: performance regression (was b44 driver problem?) From: Thomas Gleixner To: Stephen Hemminger Cc: Ulrich Drepper , Maximilian Engelhardt , Michael Buesch , linux-kernel , linux-wireless , Arnaldo Carvalho de Melo , Jeff Garzik , Gary Zambrano , netdev@vger.kernel.org, Andrew Morton , Ingo Molnar In-Reply-To: <20070604095924.651d91c8@freepuppy> References: <20070525172431.60affaca@freepuppy> <200705281944.05030.maxi@daemonizer.de> <1180380230.3657.3.camel@chaos> <200706031826.06891.maxi@daemonizer.de> <1180939188.4404.5.camel@chaos> <20070604090918.42386fbb@freepuppy> <1180974958.4404.24.camel@chaos> <20070604095924.651d91c8@freepuppy> Content-Type: text/plain Date: Mon, 04 Jun 2007 19:32:48 +0200 Message-Id: <1180978368.4404.29.camel@chaos> Mime-Version: 1.0 X-Mailer: Evolution 2.10.1 (2.10.1-4.fc7) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1489 Lines: 43 On Mon, 2007-06-04 at 09:59 -0700, Stephen Hemminger wrote: > > > gettimeofday({1180973726, 982754}, NULL) = 0 > > > recv(4, "\0\0\0\0\0\0\0\1\0\0\23\211\0\0\0\0\0\0\0\0\377\377\364"..., 8192, 0) = 8192 > > > gettimeofday({1180973726, 983790}, NULL) = 0 > > > > Well, gettimeofday() is not affected by the highres code, but > > > > > nanosleep({0, 0}, NULL) = 0 > > > nanosleep({0, 0}, NULL) = 0 > > > > is. The nanosleep call with a relative timeout of 0 returns immediately > > with highres enabled, while it sleeps at least until the next tick > > arrives when highres is off. Are there more of those stupid sleeps in > > the code ? > > GLIBC pthread_mutex does it, YES it is a problem! > Looks like the old behavior is required for ABI compatibility. > > iperf server has several threads. One thread is using pthread_mutex_lock > to wait for the other thread. It looks like pthread_mutex_lock is using > nanosleep as yield(). I doubt that. This is in the iperf code itself. void thread_rest ( void ) { #if defined( HAVE_THREAD ) #if defined( HAVE_POSIX_THREAD ) // TODO add checks for sched_yield or pthread_yield and call that // if available usleep( 0 ); ----------^^^^ It results in a nanosleep({0,0}, NULL) tglx - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/