Re: [PATCH net-next] softirq: reduce latencies

From: Rick Jones
Date: Thu Jan 03 2013 - 14:41:26 EST

On 01/03/2013 05:31 AM, Eric Dumazet wrote:
A common network load is to launch ~200 concurrent TCP_RR netperf
sessions like the following

netperf -H remote_host -t TCP_RR -l 1000

And then you can launch some netperf asking P99_LATENCY results :

netperf -H remote_host -t TCP_RR -- -k P99_LATENCY

In terms of netperf overhead, once you specify P99_LATENCY, you are already in for the pound of cost but only getting the penny of output (so to speak). While it would clutter the output, one could go ahead and ask for the other latency stats and it won't "cost" anything more:


Additional information about how the omni output selectors work can be found at

happy benchmarking,

rick jones

BTW - you will likely see some differences between RT_LATENCY, which is calculated from the average transactions per second, and MEAN_LATENCY, which is calculated from the histogram of individual latencies maintained when any of the _LATENCY outputs other than RT_LATENCY is requested. Kudos to the folks at Google who did the extensions to the then-existing histogram code to enable it to be used for more reasonably accurate statistics.

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