Re: [Gems-users] user misses

[Huan Fang <huanf@xxxxxx>]

Hi Dan,


I also guess this might be  the reason. But I get similar results with 
smaller cache size.
For 4 cores, it's configured with 32KB+32KB L1 and 512KB L2 per 
processor. And I have tried 8KB+8KB L1 and 32 KB L2 for 16 cores, which 
should be very small for the unbounded working set. But the misses are 
still around 1~2K.
I use magic instructions for both cases, only parallel part are loaded 
with ruby.
Regards,
Huan
> Could it be that your workling set size fits in 16 caches but not in 4 
> caches? AKA what are your cache sizes and configurations and what is 
> the data set size?
> Also, what mechanism are you using to start/stop simulation?
>
> Regards,
> Dan
>
> On Thu, Jul 17, 2008 at 12:01 PM, Huan Fang <huanf@xxxxxx 
> <mailto:huanf@xxxxxx>> wrote:
>     Hi All,
>
>
>     I have met a real strange problem that concerns user misses. When
>     I run
>     a parallel application on 4cores, the misses are normal:
>
>     Total_misses: 3909948
>     total_misses: 3909948 [ 988120 975421 973131 973276 ]
>     user_misses: 3864534 [ 951449 972051 970646 970388 ]
>     supervisor_misses: 45414 [ 36671 3370 2485 2888 ]
>
>     98% of total misses  are user misses.
>
>     But with 16 core configuration, the application finishes really fast
>     (only 5% ruby cycles compared to 4-core), and the user misses are
>     close
>     to 0:
>     Total_misses: 1597
>     total_misses: 1597 [ 174 14 1 4 52 34 3 11 80 10 37 36 1105 1 1 34 ]
>     user_misses: 25 [ 5 0 0 0 3 4 0 0 0 0 0 1 12 0 0 0 ]
>     supervisor_misses: 1572 [ 169 14 1 4 49 30 3 11 80 10 37 35 1093 1
>     1 34 ]
>
>
>     I am sure ruby records the same area of the application. But the
>     result
>     is simply unreasonable. Is there any thing I didn't notice?
>
>     -Huan
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