Re: Linux Zero Copy

From: Nagendra Singh Tomar (nagendra_tomar@adaptec.com)
Date: Wed Aug 13 2003 - 23:20:09 EST


Why do we not have a recvfile() also which copies data from the socket
directly to a file (page cache).

Thanx
tomar

On Wed, 13 Aug 2003, Tomar, Nagendra wrote:

> Jamie,
> Thanx for ur reply. So this means that this Zero Copy can only
> be
> used by senders who have to send data from a "file" that supports mmap.
> I
> just can't fill a buffer in userland and expect it to be sent via Zero
> Copy.
> Your pointer though clears all my confusions.
>
> Thanx
> tomar
>
> On Wed, 13 Aug 2003, Jamie Lokier wrote:
>
> > Nagendra Singh Tomar wrote:
> > > Code walkthru of Linux 2.4.18 kernel reveals that we do copy from
> user
> >
> > > space for both linear and nonlinear skbuffs. What is this zerocopy
> > thing
> > > then ?
> >
> > Take a look at the sendfile() system call. There is no user space
> > data; it can do zerocopy from the page cache.
> >
> > -- Jamie
> >
>

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