Re: [Gems-users] Ruby and Simics stall flag

[Dan Gibson <degibson@xxxxxxxx>]

Loading Opal will definitely cause L1I accesses to show up, because
Simics no longer communicates directly with Ruby in that
configuration. Readers should be aware that whether or not L1I
accesses show up in Simics+Ruby configurations seems to vary depending
on whether -stall is specified *and* varies by Simics version.

Regards,
Dan

On Wed, Feb 25, 2009 at 2:38 PM, Yangchun Luo <yluo@xxxxxxxxxx> wrote:
> Interesting topic.
>
> However, my experience is that it is not the option -stall that causes L1I
> misses to show up.
>
> It is whether opal is loaded or not.
>
> I experimented with 4 core 75MHz abisko/serengeti machine
>
> With ruby loaded, -stall and no -stall, for running 75,000,000 cycles (do
> nothing)
> No L1I misses showed up.
>
> With both ruby and opal loaded,
> * with -stall, for running 5000 cycle: (do nothing)
> L1I_cache cache stats:
>   L1I_cache_total_misses: 139
>   L1I_cache_total_demand_misses: 139
>   L1I_cache_total_prefetches: 0
>   L1I_cache_total_sw_prefetches: 0
>   L1I_cache_total_hw_prefetches: 0
>   L1I_cache_misses_per_transaction: 139
>   L1I_cache_misses_per_instruction: 0.000954546
>   L1I_cache_instructions_per_misses: 1047.62
>
> * without -stall, for running 5000 cycle: (do nothing)
> L1I_cache cache stats:
>   L1I_cache_total_misses: 140
>   L1I_cache_total_demand_misses: 140
>   L1I_cache_total_prefetches: 0
>   L1I_cache_total_sw_prefetches: 0
>   L1I_cache_total_hw_prefetches: 0
>   L1I_cache_misses_per_transaction: 140
>   L1I_cache_misses_per_instruction: 0.0013147
>   L1I_cache_instructions_per_misses: 760.629
>
>
> On 3/22/07, Dan Gibson <degibson@xxxxxxxx> wrote:
>
> Aha! The difference between Ruby/Stall and Ruby/NoStall becomes clear:
>
> Ruby/Stall:
>
> L1I_cache cache stats:
>   L1I_cache_total_misses: 234
>   L1I_cache_total_demand_misses: 234
>
>   L1I_cache_total_prefetches: 0
>   L1I_cache_total_sw_prefetches: 0
>   L1I_cache_total_hw_prefetches: 0
>   L1I_cache_misses_per_transaction: 234
>   L1I_cache_misses_per_instruction: 9.00187e-05
>   L1I_cache_instructions_per_misses: 11108.8
>
>
>
> Ruby/NoStall:
>
> L1I_cache cache stats:
>   L1I_cache_total_misses: 0
>   L1I_cache_total_demand_misses: 0
>   L1I_cache_total_prefetches: 0
>   L1I_cache_total_sw_prefetches: 0
>   L1I_cache_total_hw_prefetches: 0
>
>   L1I_cache_misses_per_transaction: 0
>   L1I_cache_misses_per_instruction: 0
>   L1I_cache_instructions_per_misses: NaN
>
>
> It would seem that failing to specify -stall causes the instruction
> hierarchy to become unstallable (aka perfect). This behaviour is
>
> actually somewhat like the x86 target...
>
> Regards,
> Dan
>
> --
> Yangchun
>
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