Re: [LAU] i5 Hyper-Threading, BIOS settings and Arch n00b pointers

On Friday 29 August 2014 04:33:43 Simon Wise did opine
And Gene did reply:
> On 29/08/14 15:40, Len Ovens wrote:
> > I don't know that the physical technology matters so much as the OS
> > being hyperthreading aware and treating each pair of cores like one.
> > That is making sure that core 0 does not do anything that takes too
> > long for core 1 to meet it's dead line. I do not know if new Linux
> > kernels do this, older ones did not. They logged that the chip had
> > hyperthreading, but still seemed to treat two threads as two
> > different cores.
> >
> > Certainly, common wisdom has not kept up with tech changes. I would
> > be nice to know more.
>
> Not quite on topic, since this isn't to do with Hyper-threading, but
> certainly the Linux scheduler has been getting much more sophisticated
> in dealing with different kinds of cores ... in ARM it now schedules
> tasks for chips with some smaller cores and some faster ones, keeping
> them busy with suitable sized tasks.
>
> The ARM kernels running the most recent Samsung tablets (with 4 big
> plus 4 little cores) have this GTS in the 3.14 kernels ... it runs all
> 8 cores together assigning tasks appropriate to each, rather than just
> switching between big or little of each pair to save power. Selling
> hardware on that scale certainly brings a budget, and since the kernel
> is GPL it can't be kept in-house.
>
> Seems that 3.14 has also added a deadline-based scheduler that is
> closer to what audio needs from realtime than the extremely low
> latency preemption based on priorities that the two older realtime
> schedulers offer.
>
> http://www.linuxfoundation.org/news-media/blogs/browse/2014/01/deadline
> -scheduling-314
>
> Simon

This message is timely as I haven't tried the deadline scheduler in
several years, so I just switched the config to make it the default, and
its building now. Perhaps it will actually improve both the USB lags, and
the network video playback I get here.

Thank you for an informative post.

Cheers, Gene Heskett

-- 
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Genes Web page <http://geneslinuxbox.net:6309/gene>
US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS
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