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SubjectRe: AMIGA will use Linux, but Linux has several "multimedia-deficiencies"
Date
O> 
> Are you tested all this stuff with `hdparm -u 1' or not ? If not then it
> can be expected. Plus you can always use RTLinux if you wish ...

Yes, of course , check out my page about the details , I tested this with
various disk tuning paramenters, but it's definitively not hardware related.
I'm sure that BeOs can reach <10ms latency even if you hook up an old
PIO MODE3 IDE Disk to your (modern) mainboard, due to the ability
to easily pre-empt the IDE driver, when the audio task needs the CPU.

The important thing is that in my case , the probem is not related to
poor designed hardware, like old mainboards which block the bus during PCI
transfers to some gfx cards, or while doing disk DMA transfers.

The easiest thing to ensure this, is to test the latencies with other operating
systems on the same hardware. If Win98 can do 17ms latency, then
the 130ms latency of Linux is definitively NOT hardware realated, very simple.
RT Linux would not help much in the general multimedia case,
because it ensures that pure computing tasks communicating with the rest of
the system via shared mem, are scheduled in a "hard-realtime" fashion,
that means that you are sure your process is for example scheduled exactly 2000
times per second but you can't use any kernel service.
For specific tasks where you can write a special kernel module which does your
custom I/O (for example driving the motors of a robot), independent of the rest
of the kernel I/O layer, RT Linux works well, but if you want general purpose
I/O like disk, graphics, audio, then RT Linux can't help.

regards,
Benno.


Benno Senoner
E-Mail: sbenno@gardena.net
Linux scheduling latency benchmarks
http://www.gardena.net/benno/linux/audio


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