Message-ID: <4043227A.6050806@cyberone.com.au>
Date: Mon, 01 Mar 2004 22:46:02 +1100
From: Nick Piggin <piggin@cyberone.com.au>
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To: Con Kolivas <kernel@kolivas.org>
CC: linux kernel mailing list <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH] SMT Nice 2.6.4-rc1-mm1
References: <200403011752.56600.kernel@kolivas.org> <200403012225.59538.kernel@kolivas.org> <4043205C.7050109@cyberone.com.au> <200403012240.34535.kernel@kolivas.org>
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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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