Re: [2.4.17/18pre] VM and swap - it's really unusable

Arjan van de Ven
2002-01-09T14:51:33Z

Andrea Arcangeli wrote:
>
> On Wed, Jan 09, 2002 at 09:07:55AM -0500, Ed Sweetman wrote:
> > Ok so the medicine is worse than the disease. I take it that you only want
> > some key points made for rescheduling instead of the full preempt patch by
> > Robert. That seems logical enough. The only issue i see is that for the
>
> My ideal is to have the kernel to be as low worst latency as -preempt,
> but without being preemptive. that's possible to achieve, I don't think
> we're that far.
>
> mean latency is another matter, but I personally don't mind about mean
> latency and I much prefer to save cpu cycles instead.

hear hear!

The akpm patch is achieving a MUCH better latency than pure -preempt,
and only has 40
or so coded preemption points instead of a few hundred (eg every
spin_unlock)....

and if with 40 we can get <= 1ms then everybody will be happy; if you
want, say, 50 usec
latency instead you need RTLinux anyway. With 1ms _worst case_ latency
the "mean" latency
is obviously also very good.......