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Re: Poor thread performance on Linux vs. Solaris



On Tue, 9 Sep 2003, Bill Soudan wrote:

> > > c011e270 4046     3.25066     kunmap_atomic
> > > c011e1e0 4955     3.98097     kmap_atomic
> >
> > hm, CONFIG_HIGHPTE enabled?
> 
> The help text for HIGHPTE implies it should be enabled on systems with
> large amounts of memory - what's considered a large amount though?  We
> have 4GB on this box.

no need for HIGHPTE on 4GB boxes, in most cases. It's useful if the
combined amount of pagetable allocation gets close to 1GB - which should
clearly not be the case on your box.

you might even opt for CONFIG_4G instead of CONFIG_64GB, if there's no RAM
above 4GB physical. (check the bootup log's e820 map for the precise RAM
layout.)

> > > c0138100 24115    19.3746     do_futex
> > > c0138bcd 46827    37.622      .text.lock.futex

> Total count from the top of the oprofile results?

yes.

>  1392500

46827 in .text.lock.futex is 3% - assuming that there's only 10% idle time
in the oprofile. This is not a catastrophic figure by itself.

	Ingo




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