Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752767Ab0KDQF5 (ORCPT ); Thu, 4 Nov 2010 12:05:57 -0400 Received: from excas01.olin.edu ([209.94.128.49]:51290 "EHLO EXCAS01.olin.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751367Ab0KDQFz (ORCPT ); Thu, 4 Nov 2010 12:05:55 -0400 Message-ID: To: Chris Mason CC: Ingo Molnar , Pekka Enberg , Aidar Kultayev , , , Linus Torvalds , Andrew Morton , Jens Axboe , Subject: Re: 2.6.36 io bring the system to its knees In-Reply-To: Your message of "Tue, 02 Nov 2010 09:12:39 EDT." <20101102131239.GA8680@think> X-Mailer: MH-E 8.2; nmh 1.3; GNU Emacs 23.2.1 Date: Thu, 4 Nov 2010 12:05:41 -0400 From: Sanjoy Mahajan MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1495 Lines: 40 > So this sounds like the backup is just thrashing your cache. I think it's more than that. Starting an rxvt shouldn't take 8 seconds, even with a cold cache. Actually, it does take a while, so you do have a point. I just did echo 3 > /proc/sys/vm/drop_caches and then started rxvt. That takes about 3 seconds (which seems long, but I don't know wherein that slowness lies), of which maybe 0.25 seconds is loading and running 'date': $ time rxvt -e date real 0m2.782s user 0m0.148s sys 0m0.032s The 8-second delay during the rsync must have at least two causes: (1) the cache is wiped out, and (2) the rxvt binary cannot be paged in quickly because the disk is doing lots of other I/O. Can the system someknow that paging in the rxvt binary and shared libraries is interactive I/O, because it was started by an interactive process, and therefore should take priority over the rsync? > Does rsync have the option to do an fadvise DONTNEED? I couldn't find one. It would be good to have a solution that is independent of the backup app. (The 'locate' cron job does a similar thrashing of the interactive response.) -Sanjoy `Until lions have their historians, tales of the hunt shall always glorify the hunters.' --African Proverb -- 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/