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

[Con Kolivas]

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.

Con 
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