Messages in this thread | | | Date | Sat, 31 Mar 2007 15:04:26 +1000 | From | Nick Piggin <> | Subject | Re: [test] hackbench.c interactivity results: vanilla versus SD/RSDL |
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Xenofon Antidides wrote: > ----- Original Message ---- > From: Ingo Molnar <mingo@elte.hu> > To: Con Kolivas <kernel@kolivas.org> > Cc: linux list <linux-kernel@vger.kernel.org>; Andrew Morton <akpm@linux-foundation.org>; Mike Galbraith <efault@gmx.de> > Sent: Thursday, March 29, 2007 9:22:49 PM > Subject: [test] hackbench.c interactivity results: vanilla versus SD/RSDL > > > * Ingo Molnar <mingo@elte.hu> wrote: > > >>* Con Kolivas <kernel@kolivas.org> wrote: >> >> >>>I'm cautiously optimistic that we're at the thin edge of the bugfix >>>wedge now. > > [...] > > >>and the numbers he posted: >> >> http://marc.info/?l=linux-kernel&m=117448900626028&w=2 > > > We been staring at these numbers for while now and we come to the conclusion they wrong. > > The test is f is 3 tasks, two on different and one on same cpu as sh here: > virgin 2.6.21-rc3-rsdl-smp > top - 13:52:50 up 7 min, 12 users, load average: 3.45, 2.89, 1.51 > > PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ P COMMAND > 6560 root 31 0 2892 1236 1032 R 82 0.1 1:50.24 1 sh > 6558 root 28 0 1428 276 228 S 42 0.0 1:00.09 1 f > 6557 root 30 0 1424 280 228 R 35 0.0 1:00.25 0 f > 6559 root 39 0 1424 276 228 R 33 0.0 0:58.36 0 f > > 6560 sh is asking for 100% cpu on cpu number 1 > 6558 f is asking for 50% cpu on cpu number 1 > 6557 f is asking for 50% cpu on cpu number 0 > 6559 f is asking for 50% cpu on cpu number 0 > > So if 6560 and 6558 are asking for cpu from cpu number 1: > 6560 wants 100% and 6558 wants 50%. > 6560 should get 2/3 cpu 6558 should get 1/3 cpu
I don't think you can say that. If the 50% task alternated between long periods of running and sleeping, then the end result should approach a task that is sleeping for 50% of the time, and on the CPU 25% of the time. As the periods get shorter, then the schedulers will favour the 50% task relatively more, but details will depend on implementation.
You could have an implementation that always gives runs the 50% task when it becomes runnable, because it is decided that its priority is higher because it has been sleeping.
The only thing you can really say is that the 50% task should get between 25% and 50% (inclusive) CPU time.
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