Re: [PATCH] 2.6.0 batch scheduling, HT aware

[Valdis . Kletnieks]

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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