Re: [PLEASE-TESTME] Zerocopy networking patch, 2.4.0-1

David S. Miller (davem@redhat.com)
Tue, 9 Jan 2001 05:42:48 -0800


From: Trond Myklebust <trond.myklebust@fys.uio.no>
Date: 09 Jan 2001 14:52:40 +0100

I don't really want to be chiming in with another 'make it a kiobuf',
but given that you already have written 'do_tcp_sendpages()' why did
you make sock->ops->sendpage() take the single page as an argument
rather than just have it take the 'struct page **'?

It was like that to begin with. But to do it cleanly you have to pass
in not a vector of "pages" but a vector of "page+offset+len" triplets.

Linus hated it, and I understood why, so I reverted the API to be
single page based.

I would have thought one of the main interests of doing something
like this would be to allow us to speed up large writes to the
socket for ncpfs/knfsd/nfs/smbfs/...

This is what TCP_CORK/MSG_MORE et al. are all for, things get
coalesced perfectly. Sending in a vector of pages seems nice, but
none of the page cache infrastructure works like this, all of the core
routines work on a page at a time. It actually simplifies a lot.

The writepage interface optimizes large file writes to a socket just
fine.

Later,
David S. Miller
davem@redhat.com

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