[PATCH v3 2/5] benchtests: Add memset zero fill benchtest

[Wilco Dijkstra]

Hi Lucas,

> By doing this you are measuring just the call it self and accumulating
> the results. This is indeed not measurable for really small lengths.
> You could try moving the memset and the timing out of the loop and
> measure the time spent in multiple runs. To fix the memset you could
> memset a bigger buffer and move the s pointer on each loop. I guess this
> will reduce the variations Wilco mentioned.

That would basically end up the same as bench-memset-walk.c given that
you need a huge buffer to get reasonable accuracy (bench-memset does
8192 iterations by default, and that is still inaccurate for small sizes).
In that case it would be easier to improve bench-memset-walk.c rather than
adding yet another benchmark that is too inaccurate to be useful.

Alternatively we could use the timing loop I suggested which allows any
pattern of zero/non-zero to be tested accurately:

      TIMING_NOW (start);
      for (j = 0; j < iters; j++)
        CALL (impl, s, memset_value[j & MASK], n);
      TIMING_NOW (stop);

Cheers,
Wilco