From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <45A57333.6060904@yahoo.com.au> Date: Thu, 11 Jan 2007 10:13:55 +1100 From: Nick Piggin MIME-Version: 1.0 Subject: Re: [REGRESSION] 2.6.19/2.6.20-rc3 buffered write slowdown References: <20070110223731.GC44411608@melbourne.sgi.com> <20070110230855.GF44411608@melbourne.sgi.com> In-Reply-To: <20070110230855.GF44411608@melbourne.sgi.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: David Chinner Cc: Christoph Lameter , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: David Chinner wrote: > On Wed, Jan 10, 2007 at 03:04:15PM -0800, Christoph Lameter wrote: > >>On Thu, 11 Jan 2007, David Chinner wrote: >> >> >>>The performance and smoothness is fully restored on 2.6.20-rc3 >>>by setting dirty_ratio down to 10 (from the default 40), so >>>something in the VM is not working as well as it used to.... >> >>dirty_background_ratio is left as is at 10? > > > Yes. > > >>So you gain performance by switching off background writes via pdflush? > > > Well, pdflush appears to be doing very little on both 2.6.18 and > 2.6.20-rc3. In both cases kswapd is consuming 10-20% of a CPU and > all of the pdflush threads combined (I've seen up to 7 active at > once) use maybe 1-2% of cpu time. This occurs regardless of the > dirty_ratio setting. Hi David, Could you get /proc/vmstat deltas for each kernel, to start with? I'm guessing CPU time isn't a problem, but if it is then I guess profiles as well. Thanks, Nick -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org