Why is IOCTL_CDROM_READ_TOC so slow?

[Waldeck Schutzer]

Hi Eric,

It is very strange indeed, but I just tested it again and I'm convinced 
that on my system that call can take a few seconds. I'm also pretty sure 
there is no concurrent access to the drive and automount is not running. 
I even did this on a failsafe session just to be sure, but still the 
same thing. I wonder there is something wrong with my kernel (2.4.18), 
or worse, with my computer. On the other hand, it works pretty fast on 
Windows.

Waldeck


Eric Pouech wrote:

> Waldeck Schutzer wrote:
>
>> I just realized that IOCTL_CDROM_READ_TOC is used almost everywhere 
>> in mcicda and somewhere else, but on the other hand it is as fast as 
>> a snail. A 68-track CD took 10 minutes to scan in cdplayer and if you 
>> press play, another 10 minutes will pass before it even starts 
>> playing! It appears to be a good idea to cache the TOC somewhere, but 
>> where and how?
>
> how come you get those timings ?
> even if we read 10 times more the TOC as we need (so 700 times), it 
> means the toc reading on the CD takes 600s, so basically a second for 
> a toc reading, which could occur when the CD rom is first inserted, 
> otherwise it's crazy
> questions: do you have some other apps accessing the cdrom (another 
> playback app, automount...) ?
>
> A+
>
>