Messages in this thread Patch in this message | | | Subject | Re: [PATCH] x86: Run checksumming in parallel accross multiple alu's | From | Eric Dumazet <> | Date | Mon, 14 Oct 2013 15:18:47 -0700 |
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On Mon, 2013-10-14 at 14:19 -0700, Eric Dumazet wrote: > On Mon, 2013-10-14 at 16:28 -0400, Neil Horman wrote: > > > So, early testing results today. I wrote a test module that, allocated a 4k > > buffer, initalized it with random data, and called csum_partial on it 100000 > > times, recording the time at the start and end of that loop. Results on a 2.4 > > GHz Intel Xeon processor: > > > > Without patch: Average execute time for csum_partial was 808 ns > > With patch: Average execute time for csum_partial was 438 ns > > Impressive, but could you try again with data out of cache ?
So I tried your patch on a GRE tunnel and got following results on a single TCP flow. (short result : no visible difference)
Using a prefetch 5*64([%src]) helps more (see at the end)
cpus : model name : Intel Xeon(R) CPU X5660 @ 2.80GHz
Before patch :
lpq83:~# ./netperf -H 7.7.8.84 -l 20 -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 20.00 7651.61 2.51 5.45 0.645 1.399
After patch :
lpq83:~# ./netperf -H 7.7.8.84 -l 20 -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 20.00 7239.78 2.09 5.19 0.569 1.408
Profile on receiver
PerfTop: 1358 irqs/sec kernel:98.5% exact: 0.0% [1000Hz cycles], (all, 24 CPUs) ------------------------------------------------------------------------------------------------------------------------------------------------------------
19.99% [kernel] [k] csum_partial 7.04% [kernel] [k] copy_user_generic_string 4.92% [bnx2x] [k] bnx2x_rx_int 3.50% [kernel] [k] ipt_do_table 2.86% [kernel] [k] __netif_receive_skb_core 2.35% [kernel] [k] fib_table_lookup 2.19% [kernel] [k] netif_receive_skb 1.87% [kernel] [k] intel_idle 1.65% [kernel] [k] kmem_cache_alloc 1.64% [kernel] [k] ip_rcv 1.51% [kernel] [k] kmem_cache_free
And 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 index 9845371..f0e10fc 100644 --- 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" + "addq 0*8(%[src]),%[res]\n\t" "adcq 1*8(%[src]),%[res]\n\t" "adcq 2*8(%[src]),%[res]\n\t" "adcq 3*8(%[src]),%[res]\n\t"
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