Re: [hatari-devel] Re: Profiler - long history

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 18/05/2015 20:46, Nicolas Pomarède a écrit :

> It depends on the cpu. 68020 only has one cache for instructions. 68030
> and 68040 have 2 caches, one for instructions and one for data.

Hi

Code updated. As indicated, 68030/40/60 also have a data cache, so I 
added more variables to track this :

typedef struct {
        int     I_Cache_miss;
        int     I_Cache_hit;
        int     D_Cache_miss;
        int     D_Cache_hit;
} cpu_instruction_t;

Eero, for now, I only updated debug/profilecpu.c to use I_Cache_miss, as 
it was before with the older version of WinUAE cpu.

To get correct cache stat, you will now need to check the cpu model and 
update profilecpu.c accordingly :

- If it's a 68020, you should use only I_Cache_miss and I_Cache_hit.

- If it's a 68030/40/60, you should use I_Cache_miss, I_Cache_hit, 
D_Cache_miss, D_Cache_hit.

Regarding data cache, it's not fully implemented yet for 68040/60, so 
results are not be trusted I guess. But 68030 cache should give correct 
values.

One thing to note about 68030 data cache is that if a long word (32 
bits) must be read, it might be stored in 2 cache's entries, depending 
if the address was aligned on 2 or 4 bytes, requiring 2 read in the cache.

So, a read for 32 bits could yield :
 - 1 hit
 - or 1 misses
 - or 1 hit and 1 miss
 - or 2 hits
 - or 2 misses

Of course, if cache is disabled, you get 0 hit and 0 miss.

Also, in order to not slow down the main cpu loop in newcpu.c, it's the 
external profiler *that must clear the hit/miss cache counter*. This 
way, counters will be cleared only when needed, no need to clear them 
every time in newcpu.c if the profiler is not used anyway.

Nicolas