Re: Re: Re: HT (Hyper Threading) aware process scheduling doesn'twork as it should

From: Artem S. Tashkinov
Date: Mon Oct 31 2011 - 04:18:38 EST

> (Cc'ing more people)
> Maybe you can also show your test case here?

The test case is perfectly outlined in the first message I posted to LKML but I
can repeat it for you ( ).

On a HT enabled completely idle system run as many different tasks as you have
real CPU cores, e.g. on an Intel Core i7 2600 CPU, that will be four tasks.

For the best performance all tasks should be attached to different physical cores.
However often the opposite behaviour can be observed, the process scheduler
binds pairs of tasks to virtual HT cores of the same physical CPU module, e.g.
in theory you should get this distribution of tasks: 1:3:5:7 but often I get this
distribution 1:6:7:8 (three physical cores loaded instead of four) or 1:2:7:8 (two
physical cores loaded instead of four).

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