Messages in this thread | | | Date | Sun, 13 Oct 2013 08:53:44 -0400 | From | Neil Horman <> | Subject | Re: [PATCH] x86: Run checksumming in parallel accross multiple alu's |
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On Sat, Oct 12, 2013 at 03:29:24PM -0700, H. Peter Anvin wrote: > On 10/11/2013 09:51 AM, Neil Horman wrote: > > Sébastien Dugué reported to me that devices implementing ipoib (which don't have > > checksum offload hardware were spending a significant amount of time computing > > checksums. We found that by splitting the checksum computation into two > > separate streams, each skipping successive elements of the buffer being summed, > > we could parallelize the checksum operation accros multiple alus. Since neither > > chain is dependent on the result of the other, we get a speedup in execution (on > > hardware that has multiple alu's available, which is almost ubiquitous on x86), > > and only a negligible decrease on hardware that has only a single alu (an extra > > addition is introduced). Since addition in commutative, the result is the same, > > only faster > > On hardware that implement ADCX/ADOX then you should also be able to > have additional streams interleaved since those instructions allow for > dual carry chains. > Ok, thats a good idea, I'll look into those instructions this week Neil
> -hpa > > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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