Re: [PATCH] zerocopy NFS for 2.5.33

From: Hirokazu Takahashi (taka@valinux.co.jp)
Date: Mon Sep 09 2002 - 03:58:21 EST


Hi,

As far as I know e1000 has a feature that it can split a jumbo UDP frame
into some IP fragments.

> From: Hirokazu Takahashi <taka@valinux.co.jp>
> Date: Mon, 09 Sep 2002 16:11:23 +0900 (JST)
>
> Using TSO code is commented out at this moment as TSO for UDP isn't
> implemented yet. I'm waiting for it so that we would remove "#ifdef NotYet"
> to send jumbo UDP frames without any fragmentation and any checksumming.
> Then I hope we will get great performance.
>
> Actually, device interface for what could be used is there, see
> NETIF_F_FRAGLIST. No devices set this and IP never makes use of it
> yet though :-)
>
> Acenic and Tigon3 will be able to do this, probably e1000 has this
> feature as well.
>
> But it does not work how you imagine. One passes already fragmented
> list of packets to card, and it can checksum the packet if you tell it
> which descriptor is first of fragmented frame and which is last.
>
> It does not do the fragmentation of UDP frames for you, only
> checksumming of UDP portion. No card does what you mention.
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