Re: Linux 2.6.17-rc2

[Nick Piggin]

Linh Dang wrote:
> Jens Axboe <axboe@xxxxxxx> wrote:

> > DVD burning probably isn't a good splice fit, since you need to do
> > more than actually just point the device at the data. SG_IO is
> > already zero-copy as it maps the user data into the kernel without
> > copying, so there's very little room for improvement there to begin
> > with.
>
>
> DVD burning on linux is mostly:
>
>         mkisofs .... | growisofs ....
>
> Ideally, on mkisofs side, we'd be able to:
>
>   - write some data/padding into the pipe
>   - splice a HUGE file into the pipe
>   - write some data/padding into the pipe
>   - splice a HUGE file into the pipe
>   ...
>
> On growisofs side, we'd be able to:
>
>   - send some commands
>   - splice N MBs of data from the pipe to the driver
>   - send some commands
>   - splice M MBs of data from the pipe to the driver
>   ...
>
> What'd be nice is an ioctl to change the size of the pipe between
> mkisofs and growisofs.

I don't see why the pipe buffers would be a problem though. It isn't
like you've lost any of the pagecache buffering (eg. from readahead)
or the application level buffering.

--
SUSE Labs, Novell Inc.
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