Re: dvd+rw-tools update [6.0, DVD-R DL]

[Joerg Schilling <schilling@fokus.fraunhofer.de>]

Matthias Andree <matthias.andree@gmx.de> wrote:

> >> You said star doesn't run as fast on Linux as Solaris, you can probably 
> >> fix that problem by using O_DIRECT, so the writes and reads don't 
> >> compete for the same buffer memory.
> >
> > And I already mentioned that it is higly improbable that O_DIRECT will
> > speed up on Linux. A better buffer cache (this means improving Linux) helps 
> > much more than avoiding it.
>
> How would a buffer cache improve the situation for star? I may have
> missed the beginning of the discussion, but caching
> write-once-then-forget data seems pointless.

A buffer cache usually does read-ahead and (in case it is well-developed)
clustering. 

As I already mentioned, the result from a short star test with O_DIRECT
verifies that O_DIRECT makes programs like star nearly 30 slower.

This is nothing new. Similar results have been made many years ago with
similar features on other platforms. The only exception so far was DG-UX
but DG-UX has really slow buffered I/O by default.

Jörg

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