Re: [PATCH] SMT Nice 2.6.4-rc1-mm1

[Nick Piggin]

Con Kolivas wrote:

> On Mon, 1 Mar 2004 10:37 pm, Nick Piggin wrote:
>
> > Con Kolivas wrote:
> >
> > > On Mon, 1 Mar 2004 05:52 pm, Con Kolivas wrote:
> > >
> > > > This patch provides full per-package priority support for SMT processors
> > > > (aka pentium4 hyperthreading) when combined with CONFIG_SCHED_SMT.
> > > And here are some benchmarks to demonstrate what happens.
> > > P4 3.06Ghz booted with bios HT off as UP (up), SMP with mm1(mm1), SMP with
> > > mm1-smtnice(sn)
> > Pretty impressive numbers.
> >
> > How does it go on the desktop when running mprime at nice +19?
> > How much worse can latencies of the niced tasks become? Any idea?
>
> Worst case scenario is easy to model; if a nice -19 task starts at exactly the 
> same time as a nice +19 task, the timeslices are 200 and 10ms. On 
> uniprocessor the nice+19 task will wait _at least_ 200 ms. On SMT nice SMP it 
> will be 200 - (200 * 15 / 100) so 170ms. That is of course worst case 
> scenario and still better than UP since the latency will be less, the task 
> will definitely start (interactive reinsertion wont affect it) and it will be 
> on a second runqueue.

OK thats good. I'm still not exactly how to generalise the cpu power
/ impact stuff, but that isn't critical. It should be done some time
though.

I'd be happy to see this patch in -mm. As Con mentioned, it would be
probably good to merge it one major release after base sched domains
is merged (if ever).

Thanks Con.

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