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Message-ID: <c565abbb0710180854j6f2f756sdd390161bafd1c4a@mail.gmail.com> Date: Thu, 18 Oct 2007 16:54:35 +0100 From: "Matthew Faulkner" <matthew.faulkner@...il.com> To: netdev@...r.kernel.org Subject: Throughput Bug? Hey all I'm using netperf to perform TCP throughput tests via the localhost interface. This is being done on a SMP machine. I'm forcing the netperf server and client to run on the same core. However, for any packet sizes below 523 the throughput is much lower compared to the throughput when the packet sizes are greater than 524. 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. MBytes /s % S % S us/KB us/KB 65536 65536 523 30.01 81.49 50.00 50.00 11.984 11.984 65536 65536 524 30.01 460.61 49.99 49.99 2.120 2.120 The chances are i'm being stupid and there is an obvious reason for this, but when i put the server and client on different cores i don't see this effect. Any help explaining this will be greatly appreciated. Machine details: Linux 2.6.22-2-amd64 #1 SMP Thu Aug 30 23:43:59 UTC 2007 x86_64 GNU/Linux sched_affinity is used by netperf internally to set the core affinity. I tried this on 2.6.18 and i got the same problem! - 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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