Messages in this thread | | | Subject | Re: [PATCH] I3 sched tweaks... | From | Justin Carlson <> | Date | 16 Jan 2002 16:19:05 -0500 |
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On Wed, 2002-01-16 at 16:10, Robert Love wrote: > On Wed, 2002-01-16 at 17:46, Ingo Molnar wrote: > > > we pass pointers across functions regularly, even if the pointer could be > > calculated within the function. We do this in the timer code too. It's > > slightly cheaper to pass an already existing (calculated) 'current' > > pointer over to another function, instead of calculating it once more in > > that function. This will be especially true once we make 'current' a tiny > > bit more expensive (Alan's kernel stack coloring rewrite will do that i > > think, it will be one more instruction to get 'current'.) > > Maybe we should benchmark it? It is very easy to calculate current. > > Certainly I see the benefit if we start coloring the pointer (it adds 2 > instructions I believe) but let's make sure it is worth passing another > 32-bit argument. It could very well be, schedule_tick is called > enough...
Don't forget that, in non-x86 land, current tends to be just kept in a register. No computations required. Certainly passing it around on, e.g. mips is a clear loss.
-Justin
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