Re: [Bugme-new] [Bug 12562] New: High overhead while switching orsynchronizing threads on different cores

[Peter Zijlstra]

On Wed, 2009-01-28 at 23:25 +0100, Thomas Pilarski wrote:
> Am Mittwoch, den 28.01.2009, 12:56 -0800 schrieb Andrew Morton: 
> 
> > (There's testcase code in the bugzilla report)
> > 
> > (Seems to be a regression)
> 
> There is a regression, because of the improved cpu switching. The
> problem exists in every kernel. 

This is a contradiction in terms - twice.

If it is a regression, then clearly things haven't improved.

If it is a regression, state clearly when it worked last. If it never
worked, it cannot be a regression.

> I takes a lot of time to switch between the threads, when they are
> executed on different cores.
> Perhaps of the big buffer size of 512KB?

Of course, pushing 512kb to another cpu means lots and lots of cache
misses.

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