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Re: [e1000 2.6 10/11] TxDescriptors -> 1024 default

To: Jeff Garzik <jgarzik@xxxxxxxxx>
Subject: Re: [e1000 2.6 10/11] TxDescriptors -> 1024 default
From: Ben Greear <greearb@xxxxxxxxxxxxxxx>
Date: Thu, 11 Sep 2003 12:45:55 -0700
Cc: "Feldman, Scott" <scott.feldman@xxxxxxxxx>, netdev@xxxxxxxxxxx, ricardoz@xxxxxxxxxx
In-reply-to: <3F60CA6D.9090503@pobox.com>
Organization: Candela Technologies
References: <Pine.LNX.4.44.0309081953510.1261-100000@localhost.localdomain> <3F60CA6D.9090503@pobox.com>
Sender: netdev-bounce@xxxxxxxxxxx
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.5b) Gecko/20030827
Jeff Garzik wrote:
Feldman, Scott wrote:

* Change the default number of Tx descriptors from 256 to 1024.
  Data from [ricardoz@xxxxxxxxxx] shows it's easy to overrun
  the Tx desc queue.



All e1000 patches applied except this one.

Of _course_ it's easy to overrun the Tx desc queue. That's why we have a TX queue sitting on top of the NIC's hardware queue. And TCP socket buffers on top of that. And similar things.

Descriptor increases like this are usually the result of some sillyhead blasting out UDP packets, and then wondering why he sees packet loss on the local computer (the "blast out packets" side).

Erm, shouldn't the local machine back itself off if the various queues are full? Some time back I looked through the code and it appeared to. If not, I think it should.


You're just wasting memory.

    Jeff





--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc  http://www.candelatech.com



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