Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751210AbXBULHh (ORCPT ); Wed, 21 Feb 2007 06:07:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751204AbXBULHh (ORCPT ); Wed, 21 Feb 2007 06:07:37 -0500 Received: from relay.2ka.mipt.ru ([194.85.82.65]:48498 "EHLO 2ka.mipt.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751203AbXBULHf (ORCPT ); Wed, 21 Feb 2007 06:07:35 -0500 Date: Wed, 21 Feb 2007 14:06:34 +0300 From: Evgeniy Polyakov To: bert hubert Cc: Andi Kleen , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: all syscalls initially taking 4usec on a P4? Re: nonblocking UDPv4 recvfrom() taking 4usec @ 3GHz? Message-ID: <20070221110634.GA30394@2ka.mipt.ru> References: <20070219231447.GA4400@outpost.ds9a.nl> <20070220162714.GA3245@outpost.ds9a.nl> <20070220164124.GA24930@2ka.mipt.ru> <20070220170232.GA4730@outpost.ds9a.nl> <20070220171120.GD24930@2ka.mipt.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=koi8-r Content-Disposition: inline In-Reply-To: <20070220171120.GD24930@2ka.mipt.ru> User-Agent: Mutt/1.5.9i X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-3.0 (2ka.mipt.ru [0.0.0.0]); Wed, 21 Feb 2007 14:07:27 +0300 (MSK) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2146 Lines: 45 Here is data for 50 bytes reading for essentially idle machine (core duo 2.4 ghz): delta for syscall: 3326961404-3326969261: 7857 cycles = 3.273750 us delta for syscall: 3326975687-3326980979: 5292 cycles = 2.205000 us delta for syscall: 3327199967-3327205583: 5616 cycles = 2.340000 us delta for syscall: 3327208706-3327214817: 6111 cycles = 2.546250 us delta for syscall: 3327442427-3327450446: 8019 cycles = 3.341250 us delta for syscall: 3327453281-3327459104: 5823 cycles = 2.426250 us delta for syscall: 3327462002-3327466844: 4842 cycles = 2.017500 us delta for syscall: 3327726809-3327733451: 6642 cycles = 2.767500 us delta for syscall: 3327736178-3327741947: 5769 cycles = 2.403750 us delta for syscall: 3327968972-3327974264: 5292 cycles = 2.205000 us delta for syscall: 3327977981-3327984506: 6525 cycles = 2.718750 us delta for syscall: 3327987215-3327991958: 4743 cycles = 1.976250 us delta for syscall: 3328245416-3328252058: 6642 cycles = 2.767500 us delta for syscall: 3328258646-3328264172: 5526 cycles = 2.302500 us and sometimes (frequently enough) delta for syscall: 1937450129-1937469011: 18882 cycles = 7.867500 us delta for syscall: 1956633332-1956654248: 20916 cycles = 8.715000 us delta for syscall: 1995042065-1995061703: 19638 cycles = 8.182500 us delta for syscall: 2014239488-2014257992: 18504 cycles = 7.710000 us delta for syscall: 2016294674-2016316202: 21528 cycles = 8.970000 us delta for syscall: 2054518259-2054537447: 19188 cycles = 7.995000 us delta for syscall: 2071839668-2071857146: 17478 cycles = 7.282500 us But there is even following sometimes: delta for syscall: 3271734859-3271872037: 137178 cycles = 57.157501 us Queue of the non-blocking socket is being kept full by another host which sends udp with 40k chunks per socket write. Reading /dev/zero in chunks of 50 bytes ends up with about 190 nanosecond on that machine. -- Evgeniy Polyakov - 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/