Re: [Gems-users] How to identify cache hit rate in Ruby?

[Mike Marty <mikem@xxxxxxxxxxx>]

With REMOVE_DCACHE_FAST_PATH (or whatever the name is) is set to 
"false", the Ruby sequencer directly accesses the L1 cache objects to 
determine a hit.  If there is an L1 hit, then the L1 cache controller is 
not invoked and you will not see "Load, Ifetch, and Store" events.  If 
you want to  see these events in the controllers, then set the above 
flag to "true". 

--Mike



Lei Yang wrote:
> But wait, when I compare the sum of L1D and L1I misses,  and the sum
> of L1 Load, Ifetch, and Store, they are exactly the same, does this
> mean that all L1 access are misses?
>
> Lei
>
> On 11/1/07, Lei Yang <lei.d.yang@xxxxxxxxx> wrote:
>   
> > Thanks Mike!
> >
> > In addition to the simics driver transaction results stats, could we
> > also look at the chip stats? (Right below the transaction results
> > stats, which I didn't notice before).
> >
> > Chip Stats
> > ----------
> >
> >  --- L1Cache ---
> >  - Event Counts -
> > Load  4775
> > Ifetch  10102
> > Store  25032
> >
> > This way, we'll know both L1 and L2 miss rates.
> >
> > Maybe we should consider include the results of miss/hit rates in the
> > L1/L2 stats in the next release.
> >
> > Lei
> > On 11/1/07, Mike Marty <mikem@xxxxxxxxxxx> wrote:
> >     
> > > misses_per_transaction simply divides the total misses by the total
> > > number of transactions.  This is not transactions in Transactional
> > > Memory.  This is workload transactions (i.e., a transaction in the
> > > Apache web server workload).
> > >
> > > You have the L1D and L1I misses.  To get the total accesses (assuming
> > > REMOVE_FAST_PATH... is set to false), look for the following:
> > >
> > > Simics Driver Transaction Results Stats
> > > ------------------------------------------
> > > Fast path: 114008467
> > > Request missed: 3926280
> > >
> > > The "Request missed" should equal the L1D and L1I misses.  The "Fast
> > > path" indicates how many requests were made to the Ruby sequencer, but
> > > hit in the L1 caches.
> > >
> > > --Mike
> > >
> > >
> > >
> > > Lei Yang wrote:
> > >       
> > > > Dear list,
> > > >
> > > > I'm wondering whether Ruby provides such statistics like cache
> > > > hit/miss rate? For example, in the following stats report from Ruby:
> > > >
> > > > L1D_cache cache stats:
> > > >   L1D_cache_total_misses: 29807
> > > >   L1D_cache_total_demand_misses: 29807
> > > >   L1D_cache_total_prefetches: 0
> > > >   L1D_cache_total_sw_prefetches: 0
> > > >   L1D_cache_total_hw_prefetches: 0
> > > >   L1D_cache_misses_per_transaction: 29807
> > > >   L1D_cache_misses_per_instruction: 0.000143247
> > > >   L1D_cache_instructions_per_misses: 6980.94
> > > >
> > > >   L1D_cache_request_type_LD:   16.0197%
> > > >   L1D_cache_request_type_ST:   82.7557%
> > > >   L1D_cache_request_type_ATOMIC:   1.22454%
> > > >
> > > >   L1D_cache_access_mode_type_SupervisorMode:   6933    23.2596%
> > > >   L1D_cache_access_mode_type_UserMode:   22874    76.7404%
> > > >   L1D_cache_request_size: [binsize: log2 max: 64 count: 29807 average:
> > > > 4.90469 | standard deviation: 4.44371 | 0 642 88 23854 5077 0 0 146 ]
> > > >
> > > > We know the total L1D cache misses, and the misses_per_instruction.
> > > > But do we know the total number of cache acesses, and thus the
> > > > hit/miss rate? Also, what does misses_per_transaction mean?
> > > >
> > > > Thank you in advance!
> > > > Lei
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