Re: Network performance - iperf
From: Rick Jones
Date: Mon Mar 29 2010 - 12:57:41 EST
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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