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SubjectRe: Network performance - iperf
Rick Jones wrote:
> I don't know how to set fixed socket buffer sizes in iperf, if you were
> running netperf though I would suggest fixing the socket buffer sizes
> with the test-specific -s (affects local) and -S (affects remote) options:
> netperf -t TCP_STREAM -H <remote> -l 30 -- -s 32K -S 32K -m 32K
> to test the hypothesis that the autotuning of the socket buffers/window
> size is allowing the windows to grow in the larger memory cases beyond
> what the TLB in your processor is comfortable with.

BTW, by default, netperf will allocate a "ring" of send buffers - the number
allocated will be one more than the socket buffer size divided by the send size
- so in the example above, there will be two 32KB buffers allocated in netperf's
send ring. A similar calculation may happen on the receive side.

That can be controlled via the global (before the "--") -W option.

-W send,recv Set the number of send,recv buffers

So, you might make the netperf command:

netperf -t TCP_STREAM -H <remote> -l 30 -W 1,1 -- -s 32K -S 32K -m 32K

happy benchmarking,

rick jones

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