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

[Bill Davidsen <davidsen@tmr.com>]

Joerg Schilling wrote:

Rob Bogus <rob23@tmr.com> wrote:

  

I'm attaching a tiny program to show that isn't the case. It's for 
zeroing out large files. If you have a disk intensive application you 
might run this to zero out say 50GB or so, and compare the impact on the 
application with dd of /dev/zero using 1024k buffer size. The program 
has compiled on rh7.2 thru FC4, SuSE, ubuntu, etc, no kernel headers or 
GNU needed, you want the POSIX behaviour, or at least I do.
    

Your program is not POSIX as it uses O_DIRECT and posix_memalign()
(the first is no POSIX at all, the latter is optional.....).
  

I made no claim that it was POSIX, but you have a point, the intended use is Linux.

But now I see where you like to use O_DIRECT.

If you use O_DIRECT for writing, it makes sense and in the same case
it makes sense to use directio(fd, DIRECTIO_ON); on Solaris.
  

By not buffering the output of mkisofs, for example, buffer space is available for reading. This makes a small improvement on a large memory, much more as the memory is smaller and read ahead could be impacted by buffering writes.

Although on Solaris, it only saves System CPU time and I cannot see
an wall clock improvement.
  

I haven't tested there, and I bet you have not tested in small memory (I use 160MB for test).

Whether this makes sense with the _output_ file from star or mkisofs
needs to be tested.....

I had not tried with the output of star, that's an interesting suggestion.

-- 
bill davidsen <davidsen@tmr.com>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979