Messages in this thread |  | | | Date | Sun, 30 Jan 2000 00:42:41 +0100 (CET) | | From | Rik van Riel <> | | Subject | Re: [PATCH] 2.3.41 scheduler change |
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On Sun, 30 Jan 2000, Jamie Lokier wrote: > Rik van Riel wrote: > > > Are you sure that CPU measurement is real? These sort of changes > > > tend to break process accounting. > > > > I agree that process accounting is kind of random. > > However, it is exactly this randomness that makes > > me believe that it really isn't a measurement fault. > > With your changes, I wouldn't be surprised to find an entirely > non-random measurement error. You're messing with scheduling > quanta, and thats exactly where measurement tends to misrepresent > what's going on. But...
I'm not at all measuring with scheduling quanta. All my patch changes is _when_ tasks get scheduled, not how much time they get.
> > Before the patch, xmms cpu usage varied between 70 > > and 95%. Now it varies between 50 and 75%, this > > looks like too big a thing to be random. > > One way to test this directly is to run a second process at the > same time that does: > > while (1) { > i = 0; > time = read_tsc (); > while (read_tsc () - time < 1 second) > i++; > printf( "%d loops per second\n", i ); > } > > The inner loop should be written to use as little cache footprint > as possible of course. > > If your patch really works, then xmms will use less CPU and this > will get more cycles.
Indeed. Maybe I'll try this when I'm fully awake again (feeling very tired now)...
cheers,
Rik -- The Internet is not a network of computers. It is a network of people. That is its real strength.
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