Re: [Valgrind-users] Compute performance lost from L2 misses

[Nguyen Vu H. <vuh...@gm...>]

2008/2/29, Van Put, Ludo <Lud...@sc...>:
> Hi,
>
>
>  >
>  > valgrind --tool=cachegrind reports that I ve 2 millions L2 misses.
>  > cachegrind manual page[1] says that a L2 miss cost around 10 cycles.
>  >
>  > So, if I am using Pentium 4, 3.2GHz ( clock rate: 3200 M
>  > cycles per second ), then the "performance lost" ( I don't
>  > know if it is the right terminology ) is:
>  >
>  > 3.2 x 1000 millions / 2,012,977 = 123 seconds.
>  >
>  > Is that correct ?
>
>
> To answer this specific questions: I think it is wrong.
>
>  2,012,977 misses x 10 cycles
>                       ------
>                       miss
>  ----------------------------  = 0.0063 seconds
>  3.2 x 1000 millions cycles
>                     ------
>                     second
>
>  But I guess L2 misses are more costly, as pointed out by Nicholas.
>
>  Hope this helps you a bit further.
Thanks for the correction.

Calibrator[1] is a small utility helps finding the relationship
between cache miss latency, cycles and performance loss in time[3]. It
also has a ( quite out-of-date ) database[2] of tested CPUs.

Mehmet, would you share your result? What is wrong with Calibrator ?

[1] http://monetdb.cwi.nl/Calibrator/
[2] http://www.cwi.nl/htbin/ins1/publications?request=search&field=KEYWORDS&pattern=Calibrator&title=Keyword:+Calibrator
[3] http://monetdb.cwi.nl/Calibrator/doc/calibrator.pdf

-- 
Best Regards,
Nguyen Hung Vu ( Nguyễn Vũ Hưng )
vuhung16plus{remove}@gmail.dot.com
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