Re: [Gems-users] High IFETCH ratio

[Dan Gibson <degibson@xxxxxxxx>]

I have no idea what ruby0.tracer does, actually. 
Now that I think about it, I'm not sure if Ruby even sees IFETCH for every instruction when running under Simics, or just every cache line. I would think the former, because Simics shouldn't know what a 'cache line' is, but you never know.

Did you run with these magic lines?
instruction-fetch-mode instruction-fetch-trace
istc-disable
dstc-disable

Failure to use those lines would probably cause problems.

Did you invoke simics with the -stall flag? You should, if you want to see ifetches. (I think its required for Simics 3 anyway, but I don't use it myself, so again I am not sure).

Regards,
Dan

On Thu, Apr 15, 2010 at 8:00 PM, Edward Lee <edwl202@xxxxxxxxx> wrote:

Thanks Dan for the prompt answer although you make me more worried now :)

Pretty much rest of the kernels have ~1-2% IFETCH ratio out of all
events for the parallel section. Would that be because I only captured
the parallel section trace? Also, just to make sure ruby0.tracer
captures all the events that are issued from the processors right?

Regards,

Ed

On Thu, Apr 15, 2010 at 9:12 PM, Dan Gibson <degibson@xxxxxxxx> wrote:
> I would be worried if IFETCH wasn't quite high... seeing as every LD or ST
> requires an IFETCH... as do all the non-memory instructions.
>
> Regards,
> Dan
>
> On Thu, Apr 15, 2010 at 6:12 PM, Edward Lee <edwl202@xxxxxxxxx> wrote:
>>
>> Hi,
>>
>> I collected traces from (parallel sections only) my SPLASH2 runs.
>> Couple of the benchmarks (namely Barnes-16k and raytrace) show 40%
>> IFETCH count and pretty much ~1% STORE count and the rest is LOADs. Is
>> having this large IFETCH counts normal, as the rest of the suite has
>> less than 1% ratio for IFETCH events?
>>
>> Regards,
>>
>> Ed
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