On Sun, Feb 20, 2005 at 10:55:18PM +0100, Sven Neumann <sven@xxxxxxxx> wrote:
> mean that it's a stupid pthread implementation. To me this looks like
> the kernel believes that it would be better to keep the threads local
> than to move one to the other CPU.
Linux will not keep two threads running on a single cpu if both are ready
and nothing else is running, regardless of locality etc., as the kernel
lacks the tools to effectively decide wether threads should stay on a cpu
or not.
(I mean, it's of course bad to interlave operations on a per-pixel basis
instead of e.g. a per-tile basis, but the kernel will run the threads
concurrently wether or not it gets slower).
> right and using two CPUs would actually cause more overhead than it's
> worth?
That's quite possible, but IFF the kernel indeed keeps the two threads on
a single cpu then it means that both aren't ready at the same time, e.g.
due to lock contention or other things.
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