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SubjectRe: DVD blockdevice buffers
On Fri, May 18 2001, Eduard Hasenleithner wrote:
> I have a problem with the buffering mechanism of my blockdevice,
> namely a ide_scsi DVD-ROM drive. After inserting a DVD and reading
> data linearly from the DVD, an excessive amount of buffer memory gets
> allocated.
>
> This can easily be reproduced with
> cat /dev/sr0 > /dev/null
>
> Remember, nearly the same task is carried out when playing a DVD.
>
> As a result the system performance goes down. I'm still able to use
> my applications, but es every single piece of unused memory is swapped
> out, and swapping in costs a certain amount of time.

That's why streaming media applications like a dvd player should use raw
I/O -- to bypass system cache. See /dev/raw*

--
Jens Axboe

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