Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932267Ab2KWXbb (ORCPT ); Fri, 23 Nov 2012 18:31:31 -0500 Received: from mail-oa0-f46.google.com ([209.85.219.46]:37310 "EHLO mail-oa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932213Ab2KWXb3 (ORCPT ); Fri, 23 Nov 2012 18:31:29 -0500 MIME-Version: 1.0 In-Reply-To: References: <20121120180949.GG1408@quack.suse.cz> <50AF7901.20401@kernel.dk> Date: Sat, 24 Nov 2012 07:31:29 +0800 Message-ID: Subject: Re: Recent kernel "mount" slow From: Jeff Chua To: Jens Axboe , Mikulas Patocka , Lai Jiangshan Cc: Linus Torvalds , Jan Kara , lkml , linux-fsdevel Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2358 Lines: 70 On Sat, Nov 24, 2012 at 6:21 AM, Jeff Chua wrote: > On Fri, Nov 23, 2012 at 9:24 PM, Jens Axboe wrote: >> On 2012-11-22 20:21, Linus Torvalds wrote: >>> Doesn't sound like a fsdevel issue since it seems to be independent of >>> filesystems. More like some generic block layer thing. Adding Jens >>> (and quoting the whole thing) >>> >>> Jens, any ideas? Most of your stuff came in after -rc2, which would >>> fit with the fact that most of the slowdown seems to be after -rc2 >>> according to Jeff. >> >> No ideas. Looking at what went in from my side, only the rq plug sorting >> is a core change, and that should not cause any change in behaviour for >> a single device. That's commit 975927b9. >> >>> Jeff, more bisecting would be good, though. >> >> Probably required, yes... > > > This one slows mount from 0.012s to 0.168s. > > commit 62ac665ff9fc07497ca524bd20d6a96893d11071 > Author: Mikulas Patocka > Date: Wed Sep 26 07:46:43 2012 +0200 > > blockdev: turn a rw semaphore into a percpu rw semaphore > > > There were couple of more changes to percpu-rw-semaphores after > 3.7.0-rc2 and those slows mount further from 0.168s to 0.500s. I don't > really know, but I'm suspecting these. Still bisecting. > > commit 5c1eabe68501d1e1b1586c7f4c46cc531828c4ab > Author: Mikulas Patocka > Date: Mon Oct 22 19:37:47 2012 -0400 > > percpu-rw-semaphores: use light/heavy barriers > > > commit 1bf11c53535ab87e3bf14ecdf6747bf46f601c5d > Author: Mikulas Patocka > Date: Mon Oct 22 19:39:16 2012 -0400 > > percpu-rw-semaphores: use rcu_read_lock_sched I reverted these 3 patches and mount time is now 0.012s. # time mount /dev/sda1 /mnt; sync; sync; umount /mnt > commit 1a25b1c4ce189e3926f2981f3302352a930086db > Author: Mikulas Patocka > Date: Mon Oct 15 17:20:17 2012 -0400 > > Lock splice_read and splice_write functions Looks like this one is not the problem. But I reverted it anyway because it's part of the same chunk. Happy Thanksgiving! Jeff -- 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/