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

Daniel Phillips
2002-01-09T06:33:30Z

On January 9, 2002 12:26 am, Luigi Genoni wrote:
> On Tue, 8 Jan 2002, Daniel Phillips wrote:
>
> > On January 8, 2002 08:47 pm, Andrew Morton wrote:
> > > Daniel Phillips wrote:
> > > > What a preemptible kernel can do that a non-preemptible kernel can't
is:
> > > > reschedule exactly as often as necessary, instead of having lots of
extra
> > > > schedule points inserted all over the place, firing when *they* think
the
> > > > time is right, which may well be earlier than necessary.
> > >
> > > Nope. `if (current->need_resched)' -> the time is right (beyond right,
> > > actually).
> >
> > Oops, sorry, right.
> >
> > The preemptible kernel can reschedule, on average, sooner than the
> > scheduling-point kernel, which has to wait for a scheduling point to roll
> > around.
>
> mmhhh. At which cost? And then anyway if I have a spinlock, I still have
> to wait for a scheduling point to roll around.

Did you read the thread? Think about the relative amount of time spent in
spinlocks vs the amount of time spent in the regular kernel.

--
Daniel