Re: [dpdk-dev] [PATCH] Implement memcmp using AVX/SSE instructio

[Bruce Richardson <bruce.richardson@intel.com>]

On Thu, Apr 23, 2015 at 09:24:52AM +0200, Pawel Wodkowski wrote:
> On 2015-04-22 17:33, Ravi Kerur wrote:
> >+/**
> >+ * Compare bytes between two locations. The locations must not overlap.
> >+ *
> >+ * @note This is implemented as a macro, so it's address should not be taken
> >+ * and care is needed as parameter expressions may be evaluated multiple times.
> >+ *
> >+ * @param src_1
> >+ *   Pointer to the first source of the data.
> >+ * @param src_2
> >+ *   Pointer to the second source of the data.
> >+ * @param n
> >+ *   Number of bytes to compare.
> >+ * @return
> >+ *   true if equal otherwise false.
> >+ */
> >+static inline bool
> >+rte_memcmp(const void *src_1, const void *src,
> >+		size_t n) __attribute__((always_inline));
> You are exposing this as public API, so I think you should follow
> description bellow or not call this _memcmp_
> 
> int memcmp(const void *s1, const void *s2, size_t n);
> 
> The memcmp() function returns an integer less than, equal  to,  or greater
> than
>        zero  if  the  first  n  bytes  of s1 is found, respectively, to be
> less than, to
>        match, or be greater than the first n bytes of s2.
> 

+1 to this point.

Also, if I read your quoted performance numbers in your earlier mail correctly,
we are only looking at a 1-4% performance increase. Is the additional code to
maintain worth the benefit?

/Bruce

> -- 
> Pawel