From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756087Ab1AaT2f (ORCPT ); Mon, 31 Jan 2011 14:28:35 -0500 Received: from mx1.fusionio.com ([64.244.102.30]:42197 "EHLO mx1.fusionio.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753327Ab1AaT2e (ORCPT ); Mon, 31 Jan 2011 14:28:34 -0500 X-ASG-Debug-ID: 1296501852-01de290b791eb140005-xx1T2L X-Barracuda-Envelope-From: JAxboe@fusionio.com Message-ID: <4D470CA7.7020508@fusionio.com> Date: Mon, 31 Jan 2011 20:25:27 +0100 From: Jens Axboe MIME-Version: 1.0 To: Jeff Moyer CC: Vivek Goyal , linux kernel mailing list Subject: Re: [PATCH] blkio-throttle: Avoid calling blkiocg_lookup_group() for root group References: <20110117215606.GI5624@redhat.com> <20110126185729.GD6713@redhat.com> <4D470C50.6010701@kernel.dk> X-ASG-Orig-Subj: Re: [PATCH] blkio-throttle: Avoid calling blkiocg_lookup_group() for root group In-Reply-To: <4D470C50.6010701@kernel.dk> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Barracuda-Connect: mail1.int.fusionio.com[10.101.1.21] X-Barracuda-Start-Time: 1296502005 X-Barracuda-URL: http://10.101.1.180:8000/cgi-mod/mark.cgi X-Barracuda-Bayes: INNOCENT GLOBAL 0.4971 1.0000 0.0000 X-Barracuda-Spam-Score: 0.00 X-Barracuda-Spam-Status: No, SCORE=0.00 using global scores of TAG_LEVEL=1000.0 QUARANTINE_LEVEL=1000.0 KILL_LEVEL=9.0 tests= X-Barracuda-Spam-Report: Code version 3.2, rules version 3.2.2.53996 Rule breakdown below pts rule name description ---- ---------------------- -------------------------------------------------- Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2011-01-31 20:24, Jens Axboe wrote: > On 2011-01-31 20:20, Jeff Moyer wrote: >> Vivek Goyal writes: >> >>> On Mon, Jan 17, 2011 at 04:56:06PM -0500, Vivek Goyal wrote: >>>> o Jeff Moyer was doing some testing on a RAM backed disk and >>>> blkiocg_lookup_group() showed up high overhead after memcpy(). Similarly >>>> somebody else reported that blkiocg_lookup_group() is eating 6% extra >>>> cpu. Though looking at the code I can't think why the overhead of >>>> this function is so high. One thing is that it is called with very high >>>> frequency (once for every IO). >>>> >>>> o For lot of folks blkio controller will be compiled in but they might >>>> not have actually created cgroups. Hence optimize the case of root >>>> cgroup where we can avoid calling blkiocg_lookup_group() if IO is happening >>>> in root group (common case). >>>> >>>> Reported-by: Jeff Moyer >>>> Signed-off-by: Vivek Goyal >>> >>> Hi Jens, >>> >>> Do you have any concerns regarding this patch? >> >> Acked-by: Jeff Moyer >> >> Jens, this is a pretty easy performance regression fixup. I think it >> should be pulled in sooner rather than later. We've also witnessed this >> slowdown on big performance testing rigs, so it's not just a ramdisk >> issue. > > Yep, will fold it into 2.6.38, thanks! Just to be clear, it's queued up in for-linus so it will go to 2.6.38 on the next push. It was updated last week, this is what it has so far: Sergey Senozhatsky (1): loop: queue_lock NULL pointer derefence in blk_throtl_exit Stephen M. Cameron (1): cciss: make cciss_revalidate not loop through CISS_MAX_LUNS volumes unnecessarily. Tao Ma (1): blktrace: Don't output messages if NOTIFY isn't set. Tracey Dent (2): drivers/block/Makefile: replace the use of -objs with -y drivers/block/aoe/Makefile: replace the use of -objs with -y Vivek Goyal (2): cfq: rename a function to give it more appropriate name blkio-throttle: Avoid calling blkiocg_lookup_group() for root group block/blk-throttle.c | 10 +++++++++- block/cfq-iosched.c | 6 +++--- drivers/block/Makefile | 2 +- drivers/block/aoe/Makefile | 2 +- drivers/block/cciss.c | 2 +- drivers/block/loop.c | 3 +++ kernel/trace/blktrace.c | 7 +++++++ 7 files changed, 25 insertions(+), 7 deletions(-) -- Jens Axboe