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size of cache 2+ messages / 2 participants [nested] [flat]
* size of cache @ 2005-07-13 08:20 Jean-Max Reymond <jmreymond@gmail.com> 0 siblings, 1 reply; 2+ messages in thread From: Jean-Max Reymond @ 2005-07-13 08:20 UTC (permalink / raw) To: pgsql-performance with my application, it seems that size of cache has great effect: from 512 Kb of L2 cache to 1Mb boost performance with a factor 3 and 20% again from 1Mb L2 cache to 2Mb L2 cache. I don't understand why a 512Kb cache L2 is too small to fit the data's does it exist a tool to trace processor activity and confirm that processor is waiting for memory ? does it exist a tool to snapshot postgres activity and understand where we spend time and potentialy avoid the bottleneck ? thanks for your tips. -- Jean-Max Reymond CKR Solutions Open Source Nice France http://www.ckr-solutions.com ^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: size of cache @ 2005-07-13 16:07 Simon Riggs <simon@2ndquadrant.com> parent: Jean-Max Reymond <jmreymond@gmail.com> 0 siblings, 0 replies; 2+ messages in thread From: Simon Riggs @ 2005-07-13 16:07 UTC (permalink / raw) To: Jean-Max Reymond <jmreymond@gmail.com>; +Cc: pgsql-performance On Wed, 2005-07-13 at 10:20 +0200, Jean-Max Reymond wrote: > with my application, it seems that size of cache has great effect: > from 512 Kb of L2 cache to 1Mb boost performance with a factor 3 and > 20% again from 1Mb L2 cache to 2Mb L2 cache. Memory request time is the main bottleneck in well tuned database systems, so your results could be reasonable. > I don't understand why a 512Kb cache L2 is too small to fit the data's > does it exist a tool to trace processor activity and confirm that > processor is waiting for memory ? You have both data and instruction cache on the CPU. It is likely it is the instruction cache that is too small to fit all of the code required for your application's workload mix. Use Intel VTune or similar to show the results you seek. Best Regards, Simon Riggs ^ permalink raw reply [nested|flat] 2+ messages in thread
end of thread, other threads:[~2005-07-13 16:07 UTC | newest] Thread overview: 2+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2005-07-13 08:20 size of cache Jean-Max Reymond <jmreymond@gmail.com> 2005-07-13 16:07 ` Simon Riggs <simon@2ndquadrant.com>
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