On Wed, 2008-11-05 at 14:02 +0000, Mel Gorman wrote:
> @@ -127,6 +140,34 @@ void *get_huge_pages(size_t len, ghp_t flags)
> return NULL;
> }
>
> +offset:
This cache-coloring code (below) is nice. Could we move it into it's
own function though? I like the idea of caching the sysconf value, but
perhaps you could do that as a static variable within the new function.
> + /*
> + * Offset the buffer using wasted bytes to avoid using the same
> + * cache lines for the start of every buffer returned by
> + * get_huge_pages(). An small effort is made to select a random
> + * cacheline rather than sequential onces to give decent behaviour
> + * on average.
> + */
> + if (!(flags & GHP_ALIGN)) {
> + char *bytebuf = (char *)buf;
> + int numlines = wasteage / cacheline_size;
> + int line = 0;
> +
> + DEBUG("%d lines of cacheline size %ld due to %zd wastage\n",
> + numlines, cacheline_size, wasteage);
> +
> + if (numlines) {
> + line = linemod % numlines;
> + bytebuf += cacheline_size * line;
> +
> + /* Pseudo-ish random line selection */
> + linemod += len % numlines;
> + }
> + DEBUG("Using line offset %d from start\n", line);
> +
> + buf = (void *)bytebuf;
> + }
> +
> /* woo, new buffer of shiny */
> return buf;
> }
--
Adam Litke - (agl at us.ibm.com)
IBM Linux Technology Center
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