Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933193Ab2K0HkQ (ORCPT ); Tue, 27 Nov 2012 02:40:16 -0500 Received: from merlin.infradead.org ([205.233.59.134]:47475 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932143Ab2K0HkO (ORCPT ); Tue, 27 Nov 2012 02:40:14 -0500 Message-ID: <50B46E05.70906@kernel.dk> Date: Tue, 27 Nov 2012 08:38:45 +0100 From: Jens Axboe MIME-Version: 1.0 To: Jeff Chua CC: Mikulas Patocka , Lai Jiangshan , Linus Torvalds , Jan Kara , lkml , linux-fsdevel Subject: Re: Recent kernel "mount" slow References: <20121120180949.GG1408@quack.suse.cz> <50AF7901.20401@kernel.dk> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1553 Lines: 36 On 2012-11-27 06:57, Jeff Chua wrote: > On Sun, Nov 25, 2012 at 7:23 AM, Jeff Chua wrote: >> On Sun, Nov 25, 2012 at 5:09 AM, Mikulas Patocka wrote: >>> So it's better to slow down mount. >> >> I am quite proud of the linux boot time pitting against other OS. Even >> with 10 partitions. Linux can boot up in just a few seconds, but now >> you're saying that we need to do this semaphore check at boot up. By >> doing so, it's inducing additional 4 seconds during boot up. > > By the way, I'm using a pretty fast SSD (Samsung PM830) and fast CPU > (2.8GHz). I wonder if those on slower hard disk or slower CPU, what > kind of degradation would this cause or just the same? It'd likely be the same slow down time wise, but as a percentage it would appear smaller on a slower disk. Could you please test Mikulas' suggestion of changing synchronize_sched() in include/linux/percpu-rwsem.h to synchronize_sched_expedited()? linux-next also has a re-write of the per-cpu rw sems, out of Andrews tree. It would be a good data point it you could test that, too. In any case, the slow down definitely isn't acceptable. Fixing an obscure issue like block sizes changing while O_DIRECT is in flight definitely does NOT warrant a mount slow down. -- Jens Axboe -- 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/