Re: [PATCH] zerocopy NFS updated

[Hirokazu Takahashi]

Hi,

>      > Hi, I've been thinking about your comment, and I realized it
>      > was a good suggestion.  There are no problem with the zerocopy
>      > NFS, but If you want to use UDP sendfile for streaming or
>      > something like that, you wouldn't get good performance.
> 
> Surely one can work around this in userland without inventing a load
> of ad-hoc schemes in the kernel socket layer?
> 
> If one doesn't want to create a pool of sockets in order to service
> the different threads, one can use generic methods such as
> sys_readahead() in order to ensure that the relevant data gets paged
> in prior to hogging the socket.

That makes sense.
It would work good enough in many cases, though it would be hard to
make sure that it really exists in core before sendfile().

> There is no difference between UDP and TCP sendfile() in this respect.

Yes.
And it seems to be more important on UDP sendfile().
processes or threads sharing the same UDP socket would affect each other,
while processes or threads on TCP sockets don't care about it as TCP
connection is peer to peer.

Thank you,
Hirokazu Takahashi.