linux-kernel - Re: disk IO directly from PCI memory to block device sectors

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Message-ID: <20081002163205.GJ19428@kernel.dk>
Date:	Thu, 2 Oct 2008 18:32:05 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Leon Woestenberg <leon.woestenberg@...il.com>
Cc:	"Leisner, Martin" <Martin.Leisner@...ox.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	marty <martyleisner@...oo.com>, linux-kernel@...r.kernel.org
Subject: Re: disk IO directly from PCI memory to block device sectors

On Thu, Oct 02 2008, Leon Woestenberg wrote:
> Hello Jens,
> 
> On Wed, Oct 1, 2008 at 9:05 PM, Jens Axboe <jens.axboe@...cle.com> wrote:
> > On Mon, Sep 29 2008, Jens Axboe wrote:
> >> On Fri, Sep 26 2008, Leisner, Martin wrote:
> >> IMHO, this interface totally rocks. It's really async like splice was
> >
> > Alright, so this one actually works :-)
> > Apart from fixing the bugs in it, it's also more clever in using the bio
> > for the write part. It'll reuse the same bio in the splice actor until
> > it's full, only then submitting it and allocating a new one. The read
> > part works the same way.
> >
> I have been following this thread trying to grasp a very nifty use
> case (high speed acquisition and storage of data) of splice.
> 
> I think it would make a perfect example of splice functionality.
> 
> What would the user space part look like to exercise this interface?

Download:

http://brick.kernel.dk/snaps/splice-git-latest.tar.gz

which has lots of little examples for splice. You would want to do
something ala

# splice-in /dev/my-pci-device | splice-out /dev/sda

in one app of course, but take a look at the examples and get a feel for
the interface...

BTW, in my splice branch I have this queued as well. Not going anywhere
for now, but should get updated and tested every now and then.

http://git.kernel.dk/?p=linux-2.6-block.git;a=shortlog;h=refs/heads/splice

-- 
Jens Axboe

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