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Re: Growisofs input cache --> Patch

David Weisgerber wrote:
On Saturday 06 December 2008 12:35:14 Thomas Schmitt wrote:

David Weisgerber wrote:
So I will create a patch which adds such a switch to growisofs
Andy Polyakov wrote earlier:
There is a way to open image without O_DIRECT and without modifying
source code: growisofs -Z /dev/cdrom=/dev/fd/0 < image.iso. Ta-dah...
In my role as a frontend programmer for
growisofs i would first try whether "Ta-dah"
is a viable workaround.

Otherwise I would need to
distribute a patched version of growisofs with turbojet...
If you rely on a growisofs novelty then
you have to urge the users to install
newest dvd+rw-tools.
"Ta-dah" - if possible - would allow a
much better decoupling of your software
and the system installed tools.

As my software is not so widely spread at the moment, I'd like to go the clean way. In addition, I think that using the pipe will create another buffer which I want to avoid. This problem is all about performance.

In the mean time I created a patch for growisofs which I hope will be included in the future (see attachment). I have run some tests with it which showed me *very* good results:
Tested: 4x2742 MB
Run 1 (w/o -no-directio): 5:37 min (for the slowest DVD recorder)
Mem:   2060284k total,   593336k used,  1466948k free,    15972k buffers

Run 2 (w -no-directio): 4:38 min (for the slowest DVD recorder)
Mem:   2060284k total,  1877136k used,   183148k free,      224k buffers

In Run 1 there were several buffer underruns which slowed the DVD recorders down. In Run 2 the buffer was always at 100% (except for the end of course) :-).

This seems reasonable, what were the performance numbers for the other system activity? I'm surprised at the underruns, cdrecord has internal fifo, and I thought you did, too. With a hacked cdrecord (around a50) the burn ran almost eight seconds slower, regardless of burn size, and never dropped below 92% full at the drive, and 70% or so in the fifo.

Bill Davidsen <davidsen@tmr.com>
 "Woe unto the statesman who makes war without a reason that will still
be valid when the war is over..." Otto von Bismark

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