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

[Christoph Hellwig]

On Tue, Jan 09, 2001 at 11:23:41AM +0100, Ingo Molnar wrote:
> 
> On Mon, 8 Jan 2001, Rik van Riel wrote:
> 
> > I really think the zerocopy network stuff should be ported to kiobuf
> > proper.
> 
> yep, we talked to Stephen Tweedie about this already, but it involves some
> changes in kiovec support and we didnt want to touch too much code for
> 2.4. In any case, the zerocopy code is 'kiovec in spirit' (uses vectors of
> struct page *, offset, size entities),

Yep.  That is why I was so worried aboit the writepages file op.
It's rather hackish (only write, looks usefull only for networking)
instead of the proposed rw_kiovec fop.

> 
> > The usefulness of the patch you posted is rather .. umm .. limited.
> > [...]
> 
> i violently disagree :-) The upcoming TUX release is based on David's and
> Alexey's cleaned-up zerocopy framework. [thus TUX and zerocopy are
> separated.] David's patch adds a *very* scalable implementation of
> zerocopy sendfile() and zerocopy sendmsg(), the panacea of fileserver
> (webserver) scalability - it can be used by Apache, Samba and other
> fileservers. The new zerocopy networking code DMA-s straight out of the
> pagecache, natively supports hardware-checksumming and highmem (64-bit DMA
> on 32-bit systems) zerocopy as well and multi-fragment DMA - no
> limitations. We can saturate a gigabit link with TCP traffic, at about 20%
> CPU usage on a 500 MHz x86 UP system. David and Alexey's patch is cool -
> check it out!

Yuck.  A new file_opo just to get a few benchmarks right ...
I hope the writepages stuff will not be merged in Linus tree
(but I wish the code behind it!)

	Christoph

-- 
Whip me.  Beat me.  Make me maintain AIX.