Re: [Bug-xorriso] Xorriso slow in ISO creation

[Wei Liu]

On Mon, Apr 07, 2014 at 12:11:33PM +0200, Thomas Schmitt wrote:
> Hi,
> 
> >   $ time xorriso -as mkisofs -R -J -o xorriso.iso xen -- -changes_pending 
> > yes
> >   real    0m1.389s
> >   $ time genisoimage -o genisoimage.iso -R -J xen
> >   real    0m0.395s
> > [...]
> > We don't quite understand why Xorriso is so much slower then
> > genisoimage.
> > (Directory xen contains ~100M random stuffs)
> 
> Possibly because libisofs builds an editable tree model of the
> ISO filesystem before it starts production.
> It may be that genisoimage just records the directories or files
> which are given to it as arguments.
> 
> In this case the slowliness should correlate with the number
> of files in the ISO image, and especially with the number of
> files in single directories if this number surpasses a few hundred.
> E.g. 100,000 files in one directory is darn slow, due to the lack
> of hashing or in-directory-tree.
> 

Re number of files, when we create CD image the difference is not that
big (12s vs 14s). When we create DVD image the difference is huge (83s
vs 12min). Is there any command line option to speed it up?

> 100 MB in 1.3 seconds indicates that the data were read from disk
> quite fast or were in RAM already. With home equipment, the low speed
> of xorriso+libisofs would probably be hidden by disk latency.
> 

Yes we had everything in page cache.

> 
> > genisoimage. Is there something wrong with the parameter we're using?
> > Are we missing something?
> 
> The parameters you used are not supposed to hamper speed.
> ("-- -changes_pending yes" is needed only if you want to create
>  empty ISOs without any input directory or file. But it does no harm
>  here.)
> 

OK.

> Do you have experience with profiling to some comprehensive
> overview ?
> 
> Do you have means to run xorriso in slow motion, so that one
> could tell from the timing of messages, at what stage of processing
> it is especially slow ?
> 

I can certainly provide more logs if you give me the runes to run. But I
probably don't have time to dig deeper. Sorry.


Thanks
Wei.

> 
> Have a nice day :)
> 
> Thomas