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SubjectRe: [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.


SUSE Labs, Novell Inc.
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