Re: [PATCH] Simple malloc benchtest.

[Siddhesh Poyarekar <siddhesh at redhat dot com>]

On Sat, Dec 21, 2013 at 04:33:03PM +0100, OndÅej BÃlka wrote:
> +void
> +do_test (size_t size)
> +{
> +  timing_t start, stop, cur;
> +  const int iters = 1<<18;
> +
> +  unsigned int r_seed = 42;
> +  void *ary[iters];
> +  size_t sizes[iters];
> +  size_t idx[iters];
> +
> +  for (int i = 0; i < iters; i++)
> +     {
> +       ary[i] = NULL;
> +       sizes[i] = size + rand_r (&r_seed) % (7 * size);
> +       idx[i] = rand_r (&r_seed) % (iters / 64);
> +     }
> +
> +  printf ("\n allocations in range %lu-%lu:", size, 8 * size);
> +
> +  TIMING_NOW (start);
> +
> +  for (int i = 0; i < iters; ++i)
> +    {
> +      free (ary[idx[i]]);
> +      ary[idx[i]] = malloc (sizes[i]);
> +    }
> +
> +  for (int i = 0; i < iters; ++i)
> +    free (ary[i]);
> +
> +  TIMING_NOW (stop);
> +  TIMING_DIFF (cur, start, stop);
> +  TIMING_PRINT_MEAN ((double) cur, (double) iters);

In addition to Wills concerns, I'd also like to see a simple
evaluation of fragmentation resulting from a sequence of allocations
and frees.  To get that you'll need to keep some blocks un-freed -
choosing those blocks would be another interesting problem.

Siddhesh