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DateTue, 14 Mar 2006 16:59:51 -0500
FromShailabh Nagar <>
SubjectRe: [Patch 0/9] Per-task delay accounting
Greg KH wrote:

>On Tue, Mar 14, 2006 at 03:49:16PM -0500, Shailabh Nagar wrote:
> >>>Greg KH wrote:>>>> >>>>>On Mon, Mar 13, 2006 at 07:40:34PM -0500, Shailabh Nagar wrote:
>>>>>>>>> >>>>>>>This is the next iteration of the delay accounting patches
>>>>last posted at>>>>http://www.ussg.iu.edu/hypermail/linux/kernel/0602.3/0893.html>>>> >>>>>>>> >>>>>>>Do you have any benchmark numbers with this patch applied and with it
>>>not applied? >>>>>> >>>>>None yet. Wanted to iron out the collection/utility aspects a bit before 
>>going into>>the performance impact.>>>>But this seems as good a time as any to collect some stats
>>using the usual suspects lmbench, kernbench, hackbench etc.
>>>> >>>>>Last I heard it was a measurable decrease for some>>>"important" benchmark results...
>>>
>>>
>>> 
>>>>>Might have been from an older iteration where schedstats was fully enabled.
>>But no point speculating....will run with this set of patches and see 
>>what shakes out.>>>>One point about the overhead is that it depends on the frequency with 
>>which data is>>collected. So a proper test would probably be a comparison of a 
>>non-patched kernel>>with>>a) patches applied but delay accounting not turned on at boot i.e. cost 
>>of the checks>>b) delay accounting turned on but not being read>> >>>>This is probably the most important one, as that is what distros will be
>looking at.  They will have to enable the option, but will not "turn it
>on".> >
I guess you meant a), not b) but yes, will run them in all these modes.

> >>>c) delay accounting turned on and data read for all tasks at some 
>>"reasonable" rate
>>
>>Will that be good  ? Other suggestions welcome.
>> 
>>>>How about real benchmarks?  The ones that the big companies look at?  I
>know you have access to them :)> >
Hmm...though you also know, from working for some "big company",  that 
it might
take a while to get such data since one has to stand in queue :-)
I'll try, and also explore the OSDL STP's DBT tests.


Thanks,
Shailabh

>thanks,>>greg k-h> >

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