> On Oct 7, 2016, at 9:17 AM, Bhanuprakash Bodireddy
> <bhanuprakash.bodire...@intel.com> wrote:
>
> prefetching the data in to the caches isn't improving the performance in
> cmap_find_batch(). Moreover its found that there is slight improvement
> in performance with out prefetching.
>
I recall doing some performance testing for this earlier, but have no records
of the system or other circumstances. Is it likely that this is at least
somewhat system and test case dependent? Also the modified batch size may be a
factor here. Anyway, I don’t currently have any proof to the contrary, so I
have no problem removing the prefetching.
However, you should also update all the comments referring to prefetching.
Jarno
> This patch removes prefetching from cmap_find_batch().
>
> Signed-off-by: Bhanuprakash Bodireddy <bhanuprakash.bodire...@intel.com>
> Signed-off-by: Antonio Fischetti <antonio.fische...@intel.com>
> ---
> lib/cmap.c | 4 ----
> 1 file changed, 4 deletions(-)
>
> diff --git a/lib/cmap.c b/lib/cmap.c
> index 8c7312d..4c34bda 100644
> --- a/lib/cmap.c
> +++ b/lib/cmap.c
> @@ -397,7 +397,6 @@ cmap_find_batch(const struct cmap *cmap, unsigned long
> map,
> ULLONG_FOR_EACH_1(i, map) {
> h1s[i] = rehash(impl, hashes[i]);
> b1s[i] = &impl->buckets[h1s[i] & impl->mask];
> - OVS_PREFETCH(b1s[i]);
> }
> /* Lookups, Round 1. Only look up at the first bucket. */
> ULLONG_FOR_EACH_1(i, map) {
> @@ -413,13 +412,11 @@ cmap_find_batch(const struct cmap *cmap, unsigned long
> map,
> if (!node) {
> /* Not found (yet); Prefetch the 2nd bucket. */
> b2s[i] = &impl->buckets[other_hash(h1s[i]) & impl->mask];
> - OVS_PREFETCH(b2s[i]);
> c1s[i] = c1; /* We may need to check this after Round 2. */
> continue;
> }
> /* Found. */
> ULLONG_SET0(map, i); /* Ignore this on round 2. */
> - OVS_PREFETCH(node);
> nodes[i] = node;
> }
> /* Round 2. Look into the 2nd bucket, if needed. */
> @@ -453,7 +450,6 @@ cmap_find_batch(const struct cmap *cmap, unsigned long
> map,
> continue;
> }
> found:
> - OVS_PREFETCH(node);
> nodes[i] = node;
> }
> return result;
> --
> 2.4.11
>
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