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Message-ID: <1414563627.631.75.camel@edumazet-glaptop2.roam.corp.google.com> Date: Tue, 28 Oct 2014 23:20:27 -0700 From: Eric Dumazet <eric.dumazet@...il.com> To: Alexei Starovoitov <alexei.starovoitov@...il.com> Cc: David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org> Subject: Re: [PATCH net-next] net: introduce napi_schedule_irqoff() On Tue, 2014-10-28 at 22:13 -0700, Alexei Starovoitov wrote: > tried 50 parallel netperf -t TCP_RR over ixgbe > and perf top were tcp stack bits, qdisc locks and netperf itself. > What do you see? You are kidding right ? If you save 30 nsec ( 2 * 15 nsec) per transaction, and rtt is about 20 usec, its a 0.15 % gain. Not bad for a trivial patch. Why are you using 50 parallel netperf, instead of trying a single netperf, as I mentioned latency impact, not overall throughput ? Do you believe typical servers in data centers are only sending & receiving bulk packets, with no interrupt, and one cpu busy polling in NAPI handler ? Every atomic op we remove/avoid, every irq masking unmasking we remove, every cache line miss or extra bus transaction we remove, TLB miss, is the path for better latency. You should take a look at recent commits I did, you'll get the general picture if you missed it. git log --oneline --author dumazet | head -100 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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