From mboxrd@z Thu Jan 1 00:00:00 1970 From: Evgeniy Polyakov Subject: Re: [tbench regression fixes]: digging out smelly deadmen. Date: Wed, 29 Oct 2008 12:14:05 +0300 Message-ID: <20081029091405.GA3780@ioremap.net> References: <20081027113306.5b1d5898@lxorguk.ukuu.org.uk> <20081027183312.GD11494@elte.hu> <20081027193933.GB2590@ioremap.net> <20081027.124848.163119274.davem@davemloft.net> <1225189462.4903.238.camel@marge.simson.net> <20081028103741.GA22319@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Mike Galbraith , David Miller , alan@lxorguk.ukuu.org.uk, jkosina@suse.cz, akpm@linux-foundation.org, a.p.zijlstra@chello.nl, rjw@sisk.pl, s0mbre@tservice.net.ru, linux-kernel@vger.kernel.org, netdev@vger.kernel.org To: Ingo Molnar Return-path: Received: from kandzendo.ru ([195.178.208.66]:45067 "EHLO tservice.net.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752831AbYJ2JOH (ORCPT ); Wed, 29 Oct 2008 05:14:07 -0400 Content-Disposition: inline In-Reply-To: <20081028103741.GA22319@elte.hu> Sender: netdev-owner@vger.kernel.org List-ID: Hi. Cooled down? Let's start over the sched vs network fight. On Tue, Oct 28, 2008 at 11:37:41AM +0100, Ingo Molnar (mingo@elte.hu) w= rote: > What's your gut feeling, is that remaining small regression scheduler= =20 > or networking related? >=20 > i'm cutting the ball in half and i'm passing over one half of it to=20 > the networking folks, because your numbers show _huge_ sensitivity in= =20 > this workload, depending on networking settings: Sorry for interrupting your conversation, Ingo, but before throwing a stone one should be clear himself, doesn't it? When you asked to test -tip tree and it was showed it regressed about 20 MB/s in my test against the last tweaks you suggested, -tip still was merged and n= o work on this issue was performed. Now previous tweaks (nohrticks and nobalalance, and although hrticks are now disabled, performance did not return to the vanilla .27 with tweaks) do not help anymore, so apparently there is additional problem. So for the reference: vanilla 27 : 347.222 no TSO/GSO : 357.331 no hrticks : 382.983 no balance : 389.802 4403b4 commit : 361.184 dirty_ratio-50 : 361.086 no-sched-tweaks : 361.367 So scheduler _does_ regress even right now when this thread is being discussed. Now let's return to the network. Ilpo J=C3=A4rvinen showed a nasty modu= lo operation in the fast path which David thinks on how to resolve it, but it happend that this change was introduced back in 2005, and although some naive change allows to increase performance upto 370 MB/s, i.e. it gained us 2.5%, this was never accounted in previous changes. So, probably, if we revert -tip merge to vanilla .27, add nohrtick patc= h and nobalance tweak _only_, and apply naive TSO patch we could bring system to 400 MB/s. Note, that .22 has 479.82 and .23 454.36 MB/s. --=20 Evgeniy Polyakov