Messages in this thread | | | Subject | Re: [PATCH] 2.6.0 batch scheduling, HT aware | From | Valdis.Kletnieks@vt ... | Date | Fri, 02 Jan 2004 16:10:21 -0500 |
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On Fri, 02 Jan 2004 12:56:16 PST, Davide Libenzi said: > On Fri, 2 Jan 2004, Bill Davidsen wrote: > > > Yes and even worse, if you stop running setiathome the scientific task > > *still* only gets half the available CPU! > > Look that this is not true. If one core is not running any task, the idle > task (if not polling) does "hlt" and the "what they call Fetch And
What Bill said was:
>> memory-bound seti&home at CPU1. Even without hyperthreading, your >> scientific task is going to run at 50% of speed and seti&home is going >> to get second half. Oops.
> Yes and even worse, if you stop running setiathome the scientific task > *still* only gets half the available CPU!
So Bill is pointing out that on a *normal* SMP, you get 50% whether or not the other processor is busy.
> The difference is that with HT running a task on one sibling actually > does (or can) slow the other. That's not true with true SMP, at least > not directly, since the resourses shared (memory and disk) are much > farther away from the CPU.
And this is where Bill talks about issues like the one you mentioned about sharing the dispatch engine.
So I think you and Bill are actually saying the same exact thing.
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