Messages in this thread | | | Date | Thu, 26 Jan 2012 11:04:29 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH v2] sched: Accelerate "pick_next_entity" under special condition |
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* Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> On Tue, 2012-01-17 at 11:04 +0800, Michael Wang wrote: > > > > > Then what if condition 1 is true now? > > > > We can see in original code, even condition 1 is true, we > > still will use value3 if condition3 is true, like this: > > > > original: > > > > condition1 condition3 result > > true true value3 > > true false value1 > > > > That means if condition3 is true, we don't care whether > > condition1 is true or not because we will finally use value3. > > Right, so from the original 8 possible states we used to evaluate 3*8 = > 24 conditionals. The new code will reduce this to 1*4 + 2*2 + 2*3 = 14. > > Now I guess the question is if it matters for the modal or average > state. > > I've applied the patch since it can't be worse, but I've no idea if it > matters or not in practice.
A before/after kernel/sched.o size comparison on 64-bit defconfig typically gives a pretty good indication whether it's a step forward or not.
Thanks,
Ingo
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