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

Lee Revell
2004-09-15T02:12:12Z

On Tue, 2004-09-14 at 21:39, William Lee Irwin III wrote:
> > 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.
>

Understood. The only dangerous change I know of in the VP patches is
the one Alan took issue with, the aforementioned removal of lock_kernel
in the tty code. IIRC this only produced a latency of about 300 usecs,
and only when switching VT's from a console to X and back. My point was
that it's quite possible that we can get OSX-like results without the
more dangerous changes.

Ingo, if you want to send me a patch set without the more controversial
changes, I can compare the performance. A diff against the latest VP
patch would be OK.

Lee