Re: [hatari-devel] Hatari data cache tests

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 19/06/2015 22:30, Douglas Little a écrit :
> Hi,
>
> One strange thing I noticed w.r.t data cache hits/misses is the apparent
> lack of impact it has on cycle timings. Hits seem to cost the same as
> misses at least in terms of the profiler results... in this case two
> different instructions with very different hit ratios have almost
> exactly the same cycle sum.
>
> $000362a0 :             move.w    a3,d0                      0.09%
> (166384, 665736, 670, 0)
> $000362a2 :             move.w    d0,d1                      0.09%
> (166384, 663084, 22, 0)
> $000362a4 :             add.w     d2,d0                      0.09%
> (166384, 665844, 695, 0)
> $000362a6 :             move.b    (a0)+,d1                   0.09%
> (166384, *1331344*, 44, 212)  <- hit ratio of 0.1%
> $000362a8 :             move.w    (a6,d1.l*2),(a1)+          0.09%
> (166384, 1999512, 715, 66190)
> $000362ac :             move.w    d0,d1                      0.09%
> (166384, 2768, 660, 0)
> $000362ae :             add.w     d2,d0                      0.09%
> (166384, 663048, 24, 0)
> $000362b0 :             move.b    (a0)+,d1                   0.09%
> (166384, *1331444*, 679, 154776) <- hit ratio of 93%
> $000362b2 :             move.w    (a6,d1.l*2),(a1)+          0.09%
> (166384, 1999176, 712, 82447)

Hi

thanks for pointing this, but just to be sure, you're running in CE 
mode, not just compatible/prefetch mode ? The later also counts cache 
hits/misses, but not accesses cycles.

But I didn't complete integrating all the cycles parts from winuae into 
hatari anyway, I plan to do this after 1.9 is released as this will 
certainly incur a lot of regression test and inner change to hatari, so 
this could be the reason.

I need to write some simple cache clear / fill cache / read data tests 
to simulate all this.

For now, the results you get could be a mix of several reasons and work 
in progress :)


Nicolas