Re: [patch] sched: fix scheduling latencies for !PREEMPT kernels

William Lee Irwin III
2004-09-15T01:39:34Z

On Tue, Sep 14, 2004 at 09:02:07PM -0400, Lee Revell wrote:
> For a generic desktop I don't think any of this makes much of a
> difference; AFAIK none of the VP testers have reported a perceptible
> difference in system responsiveness. A good point of comparison here is
> what Microsoft OS'es can do. My Windows XP setup works pretty well with
> a latency of 2.66ms or 128 frames at 48KHZ, and is rock solid at 256
> frames or 5.33ms.
> However for low latency audio Mac OS X is our real competition. OS X
> can deliver audio latencies of probably 0.5ms. There is not much point
> in going much lower than this because the difference becomes
> imperceptible and the more frequent cache thrashing becomes an issue;
> this is close enough to the limits of what sound hardware is capable of
> anyway.
> With Ingo's patches the worst case latency on the same machine as my XP
> example is about 150 usecs. So, it seems to me that Ingo's patches can
> achieve results as good or better than OSX even without the one or two
> "dangerous" changes, like the removal of lock_kernel around
> do_tty_write.

The code we're most worried is buggy, not just nonperformant.

-- wli