RE: Why dual traffic in 100Mbps envrionment is much less than 100M?

To: <iperf-users --at-- dast.nlanr.net>
Subject: RE: Why dual traffic in 100Mbps envrionment is much less than 100M?
From: "William E. Allcock" <allcock --at-- mcs.anl.gov>
Date: Fri, 28 Apr 2006 10:13:16 -0500
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A glue I found is in the case of no delay, when I set a big buffer for iperf, the NIC driver called "netif_stop_queue" many times, while with a small buffer for iperf, there is seldom. I added some debug info in NIC driver to find this.

Is this related to the problem I met? And how I can locate and solve this performance problem?

I cant be sure, but that sounds like you might be seeing what is called a "send stall", you are over-running the NIC queue. Try this (assuming you are usign eth0):

ifconfig eth0 txqueuelen 5000

and see if that makes any difference.

Thanks a lot in advance.

Follow-Ups:
- Re: Why dual traffic in 100Mbps envrionment is much less than 100M?
  - From: fu zhijun

References:
- Why dual traffic in 100Mbps envrionment is much less than 100M?
  - From: fu zhijun

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