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Message-ID: <48F7AD1A.7050309@hp.com>
Date: Thu, 16 Oct 2008 14:07:38 -0700
From: Rick Jones <rick.jones2@...com>
To: Andrew Morton <akpm@...ux-foundation.org>
CC: netdev@...r.kernel.org, bugme-daemon@...zilla.kernel.org,
arno@...o.snv.jussieu.fr, Ayaz Abdulla <aabdulla@...dia.com>
Subject: Re: [Bugme-new] [Bug 11752] New: Extremely low netperf UDP_RR throughput
for nvidia MCP65
Andrew Morton wrote:
> (switched to email. Please respond via emailed reply-to-all, not via the
> bugzilla web interface).
>
> On Mon, 13 Oct 2008 13:41:19 -0700 (PDT)
> bugme-daemon@...zilla.kernel.org wrote:
>
>
>>http://bugzilla.kernel.org/show_bug.cgi?id=11752
>>
>> Summary: Extremely low netperf UDP_RR throughput for nvidia MCP65
>> Product: Drivers
>> Version: 2.5
>> KernelVersion: from F10-Beta-x86_64-Live-KDE.iso
>> Platform: All
>> OS/Version: Linux
>> Tree: Mainline
>> Status: NEW
>> Severity: normal
>> Priority: P1
>> Component: Network
>> AssignedTo: jgarzik@...ox.com
>> ReportedBy: arno@...o.snv.jussieu.fr
>>
>>
>>Latest working kernel version: -
>>Earliest failing kernel version:
>>Distribution: F10-Beta-x86_64
>>Hardware Environment: HP Pavillon dv6820ef
>>Software Environment:
>>Problem Description: when running at 1Gbps netperf shows good performance for
>>TCP_STREAM and UDP_STREAM tests, but extremely bad performance for UDP_RR test
>>(less then 1 ping-pong a second whereas at 100Mbps performance easily reaches
>>10-20K a second)
>>
>>A friend figured out that it looks like small packets at 1Gbps are dropped
>>as being falsely considered crc-errored.
Given how netperf UDP_RR has _no_ recovery from lost datagrams, it makes
sense that performance on that test would be very low - the first lost
datagram the transactions come to a screeching halt until the
end-of-test timer expires.
Are netstat stats showing retransmissions during a TCP_STREAM test? How
about a TCP_RR test? TCP_RR might be low too, it just wouldn't
necessarily be as low since TCP will get things started again after a
loss. UDP_STREAM would just go blasting along without a care in the
world...
rick jones
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