Messages in this thread | | | Subject | Re: [PATCH] x86: Run checksumming in parallel accross multiple alu's | From | Joe Perches <> | Date | Mon, 14 Oct 2013 15:49:42 -0700 |
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On Mon, 2013-10-14 at 15:44 -0700, Eric Dumazet wrote: > On Mon, 2013-10-14 at 15:37 -0700, Joe Perches wrote: > > On Mon, 2013-10-14 at 15:18 -0700, Eric Dumazet wrote: > > > attached patch brings much better results > > > > > > lpq83:~# ./netperf -H 7.7.8.84 -l 10 -Cc > > > MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 7.7.8.84 () port 0 AF_INET > > > Recv Send Send Utilization Service Demand > > > Socket Socket Message Elapsed Send Recv Send Recv > > > Size Size Size Time Throughput local remote local remote > > > bytes bytes bytes secs. 10^6bits/s % S % S us/KB us/KB > > > > > > 87380 16384 16384 10.00 8043.82 2.32 5.34 0.566 1.304 > > > > > > diff --git a/arch/x86/lib/csum-partial_64.c b/arch/x86/lib/csum-partial_64.c > > [] > > > @@ -68,7 +68,8 @@ static unsigned do_csum(const unsigned char *buff, unsigned len) > > > zero = 0; > > > count64 = count >> 3; > > > while (count64) { > > > - asm("addq 0*8(%[src]),%[res]\n\t" > > > + asm("prefetch 5*64(%[src])\n\t" > > > > Might the prefetch size be too big here? > > To be effective, you need to prefetch well ahead of time.
No doubt.
> 5*64 seems common practice (check arch/x86/lib/copy_page_64.S)
5 cachelines for some processors seems like a lot.
Given you've got a test rig, maybe you could experiment with 2 and increase it until it doesn't get better.
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