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

[Matthias Andree <matthias.andree@gmx.de>]

Joerg Schilling schrieb am 2006-01-30:

> Bill Davidsen <davidsen@tmr.com> wrote:
> 
> > the data should be sent to the drive NOW. Eliminated writing a full CD 
> > to buffer, with data from cache, then closing the file and having the 
> > drive go dead busy for a minute.
> 
> This is a problem arising from the bad caching strategies on Linux.
> 
> Solaris starts writing short after cache memory starts filling.
> Linux just starts too late and then you need to wait ast the end.

1. this discussion is in the wrong place. Take it up to the linux lists,
but pay attention to:

2. scheduling writes is a complex matter in itself, and there is not a
single answer.  The later you start writing, the more data you have
available if the input rate is low for a while to write a large blob of
data (reducing seeks), the more opportunity you have to rearrange writes
and the lower the total amount of data to write, because updates of
yet-unwritten data do not turn into writes (I/O) but are made in-core.

It seems appropriate to support POSIX_FADV_SEQUENTIAL and
POSIX_FADV_NOREUSE (in posix_fadvise) in both the application and the
kernel if that is the actual use pattern. According to my manual pages,
Linux supports both. If it actually changes strategy, and which I/O
scheduler it uses, is a different question. Linux has several I/O
schedulers, the default appears to be the anticipatory scheduler, but it
also has CFQ and deadline schedulers.

-- 
Matthias Andree