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Re: Poor gige performance with 2.4.20-pre*

To: Richard Gooch <rgooch@xxxxxxxxxxxxxxx>
Subject: Re: Poor gige performance with 2.4.20-pre*
From: Ben Greear <greearb@xxxxxxxxxxxxxxx>
Date: Sun, 29 Sep 2002 12:32:38 -0700
Cc: netdev@xxxxxxxxxxx
Organization: Candela Technologies
References: <200209282257.g8SMvta32527@xxxxxxxxxxxxxxxxxxxxxxxx> <3D966656.7040205@xxxxxxxxxxxxxxx> <200209291922.g8TJMA312403@xxxxxxxxxxxxxxxxxxxxxxxx>
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Richard Gooch wrote:
Ben Greear writes:

Richard Gooch wrote:

 Hi, all. For a while now I've noticed poor performance with gige
cards under 2.4.19 and 2.4.20-pre*. At first I thought it was because
of the cheap-ass Addtron cards I bought (these use the ns83820 chip).
But now that the Intel E1000 cards are pretty cheap too, I've grabbed
a couple (part number: PWLA8390MT) and see the same problem. In fact,
the E1000 cards are no better than the Addtron cards. I'm using the
D-Link DGS-1008T 8-port gige switch. MTU=1500 bytes.

Try setting the TxDescriptors=4096 RxDescriptors=1024 when loading the
e1000 module, that helps tremendously when using smaller packets.

Didn't help at all. Just to summarise, I've got:
options e1000 TxDescriptors=4096 RxDescriptors=1024
net.ipv4.tcp_rmem = 262144 262144 262144
net.ipv4.tcp_wmem = 262144 262144 262144

I'm doing read(2)/write(2) to/from a user-space buffer over a TCP
socket with 256 KiB buffer size.

Is the E1000 supposed to have hardware interrupt mitigation (thus
avoiding the need for NAPI)?

NAPI did not greatly improve the performance I saw with larger packets,
but it did help with smaller (say, 60 byte) packets.

One other thing I saw with TCP connections:  They started off slow, but after
a few seconds they were reacing their peak throughput.  How long are you running
your test?



Permanent: rgooch@xxxxxxxxxxxxx
Current:   rgooch@xxxxxxxxxxxxxxx

Ben Greear <greearb@xxxxxxxxxxxxxxx>       <Ben_Greear AT>
President of Candela Technologies Inc

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