Re: zero copy

[Matt Porter <mporter@kernel.crashing.org>]

On Tue, Dec 06, 2005 at 04:06:06AM -0800, kernel coder wrote:
> hi,
>     i'm trying to track the code flow of sendfile system call.Mine
> ethernet card doesn't have scatter gather and checksum calculation
> features.So stack should be making a copy of data.
> 
> Please tell me where in sendfile code flow,check for scatter gather
> and cecksum features is made so that stack can decide whether to copy
> data from user space or not.

Is your grep really that broken? :)

net/ipv4/tcp.c:tcp_sendpage() is where you find the check and
fallback to sendmsg if you follow it through.

-Matt