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Date: Thu, 11 Jan 2007 10:13:55 +1100 From: Nick Piggin <nickpiggin@...oo.com.au> To: David Chinner <dgc@....com> CC: Christoph Lameter <clameter@....com>, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: [REGRESSION] 2.6.19/2.6.20-rc3 buffered write slowdown 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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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