Re: [PATCH] f_op->poll() without lock_kernel()

From: David S. Miller (davem@redhat.com)
Date: Fri Apr 21 2000 - 22:51:08 EST


   Date: Fri, 21 Apr 2000 23:48:52 -0400 (EDT)
   From: Alexander Viro <viro@math.psu.edu>

   On Fri, 21 Apr 2000, David S. Miller wrote:

> Some day it may be fun to mmap tcp sockets. It has to stay.

   Hey, it's your part of the tree, but... what kind of semantics one
   might want for mmap() on TCP link? I'm really curious...

For received packets, they just "appear" in the mmap'd area,
which is managed in a ring fashion using new/old indexes.
User advances "old" as received frames are no longer needed
and kernel advances "new" as new frames are received.

Transmit works similarly except that the management of the
"old" and "new" is done by the kernel and user respectively.

Essentially it's like moving the buffer management of an ethernet
driver into user space, it's similar to what the UNET project
did/proposed, except you don't need to give up all the advantages
of TCP.

It's just an idea, and one could implement this with zero
copy pretty easily with special firmware on a gbit card for
example. And it'll make happy the beowulf folks. :-)

Anyways, I'll look over your patch.

Later,
David S. Miller
davem@redhat.com

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