Re: [Xen-devel] [PATCHv3 0/4] Use ticket locks for spinlocks

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.04.15 at 12:11, <david.vrabel@xxxxxxxxxx> wrote:
> We have analysed the affect of this series on interrupt latency (by
> measuring the duration of irq disable/enable regions) and there is no
> signficant impact.
> 
> http://xenbits.xen.org/people/dvrabel/bar2_comp.png 

Thanks for doing this!

> Interestingly, the biggest offenders for long critical sections are
> bare irq disable/enable regions, and some of these are really bad (10s
> of ms)!
> 
> http://xenbits.xen.org/people/dvrabel/bar_normal_busy.png 

Despite both pictures saying micro-seconds at the respective
axis (and hence the problem not being _as bad_) - did the data
collection reveal where these IRQ disable regions are, so we
could look into eliminating them? (ISTR there being some open
coded IRQ-disable, lock, unlock, IRQ-restore/enable sequences,
but I'm not sure whether they got eliminated already.)

Jan


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