Why are sound ioctl calls so slow?

[Ian Freislich]

Mathew Kanner wrote:
> On Dec 10, Ian Freislich wrote:
> > Mathew Kanner wrote:
> > > 	My first guess would be the device is rebuilding feeder/mixer
> > > chains every time mpg123 changes format.  I would run the test one
> > > more time, disabling vchans and rate conversion.
> > > 
> > > 	sysctl hw.snd.report_soft_formats=0 hw.snd.maxautovchans=0
> > 
> > That didn't make a (noticeable) difference:
> > 
> >   4090 mpg123   0.000603 CALL  ioctl(0x3,SNDCTL_DSP_STEREO,0xbfbff864)
> >   4090 mpg123   0.026047 RET   ioctl 0
> >   4090 mpg123   0.000582 CALL  ioctl(0x3,SNDCTL_DSP_SPEED,0xbfbff864)
> >   4090 mpg123   0.017735 RET   ioctl 0
> >   4090 mpg123   0.000414 CALL  ioctl(0x3,SNDCTL_DSP_SETFMT,0xbfbff864)
> >   4090 mpg123   0.026004 RET   ioctl 0
> 
> 	You complained that mpg123 was doing hundered of system calls.
> Did that remain constant aswell?

Yes it it did.

Ian