Re: [hatari-devel] Suspicious instruction & data cache hit/miss accounting

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 06/02/2018 à 18:09, Eero Tamminen a écrit :
> I added that statistic, but now I started to wonder about terminology,
> what would be best understood by the users of the profiler.
>
> Is "prefetch" correct name for moving data from i-cache to CAHR
> register, or do people normally interpret "prefetch" to mean reading
> instructions from system RAM to i-cache? >
> I.e. maybe the zero i-cache hit/miss case should be named as:
>    "Cache holding register (CAHR) already refilled from i-cache"
>
> instead of my current "Already prefetched" name?

In fact, I don't know if all users of the profiler are aware of these 
low details of the CPU inner work, so finding a brief and correct 
wording might be difficult.

Most users who look for optimisations should try to increase hit values 
and decrease miss values, ignoring this "prefetched" case (as it's 
basically a 50% chance).

Still the motorola docs tells about CAHR in "11.2.2" :

"This long word is obtained from the instruction cache o the external 
bus in response to a prefetch request from the microsequencer."

So I think that "already prefetched" is correct.
Moving from ram to i-cache should be simply called "caching" :)

Nicolas