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

[Thomas Schmitt]

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.

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.


> 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.)

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 ?


Have a nice day :)

Thomas