Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753313AbXJAIXc (ORCPT ); Mon, 1 Oct 2007 04:23:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751629AbXJAIXZ (ORCPT ); Mon, 1 Oct 2007 04:23:25 -0400 Received: from smtp23.orange.fr ([80.12.242.97]:57608 "EHLO smtp23.orange.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751085AbXJAIXY convert rfc822-to-8bit (ORCPT ); Mon, 1 Oct 2007 04:23:24 -0400 X-ME-UUID: 20071001082020828.CA5481C0009A@mwinf2303.orange.fr Message-ID: <4700ADB7.7050102@cosmosbay.com> Date: Mon, 01 Oct 2007 10:20:07 +0200 From: Eric Dumazet User-Agent: Thunderbird 1.5.0.7 (Windows/20060909) MIME-Version: 1.0 To: Denys Cc: David Miller , linux-kernel@vger.kernel.org, netdev@vger.kernel.org Subject: Re: 2.6.21 -> 2.6.22 & 2.6.23-rc8 performance regression References: <200709301425.37564.nickpiggin@yahoo.com.au> <20070930223503.M8966@nuclearcat.com> <47008CB0.7010808@cosmosbay.com> <20071001.001259.28812610.davem@davemloft.net> <20071001080339.M21850@nuclearcat.com> In-Reply-To: <20071001080339.M21850@nuclearcat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2567 Lines: 75 Denys a écrit : > Well, i can play a bit more on "live" servers. I have now hot-swap server with > full gentoo, where i can rebuild any kernel you want, with any applied patch. > But it looks more like not overhead, load becoming high too "spiky", and it is > not just permantenly higher. Also it is not normal that all system becoming > unresposive (for example ping 127.0.0.1 becoming 300ms for period, when usage > softirq jumps to 100%). > > Could you try a pristine 2.6.22.9 and some patch in secure_tcp_sequence_number() like : --- drivers/char/random.c.orig 2007-10-01 10:18:42.000000000 +0200 +++ drivers/char/random.c 2007-10-01 10:19:58.000000000 +0200 @@ -1554,7 +1554,7 @@ * That's funny, Linux has one built in! Use it! * (Networks are faster now - should this be increased?) */ - seq += ktime_get_real().tv64; + seq += ktime_get_real().tv64 / 1000; #if 0 printk("init_seq(%lx, %lx, %d, %d) = %d\n", saddr, daddr, sport, dport, seq); Thank you > On Mon, 01 Oct 2007 00:12:59 -0700 (PDT), David Miller wrote > >> From: Eric Dumazet >> Date: Mon, 01 Oct 2007 07:59:12 +0200 >> >> >>> No problem here on bigger servers, so I CC David Miller and netdev >>> on this one. AFAIK do_gettimeofday() and ktime_get_real() should >>> use the same underlying hardware functions on PC and no performance >>> problem should happen here. >>> >> One thing that jumps out at me is that on 32-bit (and to a certain >> extent on 64-bit) there is a lot of stack accesses and missed >> optimizations because all of the work occurs, and gets expanded, >> inside of ktime_get_real(). >> >> The timespec_to_ktime() inside of there constructs the ktime_t return >> value on the stack, then returns that as an aggregate to the caller. >> >> That cannot be without some cost. >> >> ktime_get_real() is definitely a candidate for inlining especially in >> these kinds of cases where we'll happily get computations in local >> registers instead of all of this on-stack nonsense. And in several >> cases (if the caller only needs the tv_sec value, for example) >> computations can be elided entirely. >> >> It would be constructive to experiment and see if this is in fact >> part of the problem. >> > > > -- > Denys Fedoryshchenko > Technical Manager > Virtual ISP S.A.L. > > > - 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/