Messages in this thread | | | From | "Davide Libenzi" <> | Subject | Re: Auto-Adaptive scheduler - Final chapter ( the numbers ) ... | Date | Thu, 27 Jan 2000 19:21:44 +0100 |
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Thursday, January 27, 2000 6:34 PM Larry McVoy <lm@bitmover.com> wrote : > : > . the real measure of any change is whether or not it increases or > : > decreases the amount of code in the icache, the number of > : mispredicted > : > branches in the icache, the amount of data in the dcache, and > : finally, > : > any changes in the number of cache misses. > : > : This is the code [etc] > > And that code doesn't answer any of the questions posed above. Not one.
Sorry Larry but You've the patch ( code ) and the "instrument" ( code ) used for test. More You have numbers that show switching times differences. I can optimize the patch to perform even better for RQ = 2 ( move some code out of fast path ) but I think it makes no sense due to the fact that the scheduler must have a faster responses under high loads. Even if I've changed the scheduler to better perform with short RQ ( and the numbers are here ), I still think that speaking about RQ = 2 in analyzing a scheduler is a nonsense. An RQ = 2, under real charge ( if You've 2 running tasks probably Your system is not so stressed ) switch at no more than 2000 switch / sec ( statistically even less ), so to get a 5% of scheduler time You need a switch time of 25 us. This is a time that I get with RQ = 100-150 on my machine. You can state that exist machines ( slow ) in which 25 us is a typical switch time ( for RQ = 2 ), but probably that machines cannot perform 2000 switch / sec under real load. As an example my machine ( PII 400 ) with RQ = 2 has a switch time = 1.36 us ( with the patch ), so You need a machine 18.5 times slower than mine.
> for size in 0 2 4 8 10 12 14 16 18 20 22 24 26 28 30 32 > do lat_ctx -s $size 2 2 2 2 2 2 > done > > plot the results. If your L1 cache is bigger than 32K, keep going.
I'll do for sure even if I think that, as I've said to Horst, this will add a constant term that will reduce even more the percent result.
PS: Tonight ( Europe ) I can't coz I'm out for dinner, I'll run the test tomorrow night.
With respect, Davide.
-- All this stuff is IMVHO
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