Messages in this thread | | | Subject | Re: [PATCH v2 2/2] x86: add prefetching to do_csum | From | Joe Perches <> | Date | Wed, 06 Nov 2013 09:19:23 -0800 |
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On Wed, 2013-11-06 at 10:54 -0500, Neil Horman wrote: > On Wed, Nov 06, 2013 at 10:34:29AM -0500, Dave Jones wrote: > > On Wed, Nov 06, 2013 at 10:23:19AM -0500, Neil Horman wrote: > > > do_csum was identified via perf recently as a hot spot when doing > > > receive on ip over infiniband workloads. After alot of testing and > > > ideas, we found the best optimization available to us currently is to > > > prefetch the entire data buffer prior to doing the checksum [] > I'll fix this up and send a v3, but I'll give it a day in case there are more > comments first.
Perhaps a reduction in prefetch loop count helps.
Was capping the amount prefetched and letting the hardware prefetch also tested?
prefetch_lines(buff, min(len, cache_line_size() * 8u));
Also pedantry/trivial comments:
__always_inline instead of inline static __always_inline void prefetch_lines(const void *addr, size_t len) { const void *end = addr + len; ...
buff doesn't need a void * cast in prefetch_lines
Beside the commit message, the comment above prefetch_lines also needs updating to remove the "Manual Prefetching" line.
/* * Do a 64-bit checksum on an arbitrary memory area. * Returns a 32bit checksum. * * This isn't as time critical as it used to be because many NICs * do hardware checksumming these days. * * Things tried and found to not make it faster: * Manual Prefetching * Unrolling to an 128 bytes inner loop. */
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