Re: [PATCH 0/10] bulk cpu removal support

[Shaohua Li]

On Mon, 2006-05-08 at 01:29 -0500, Nathan Lynch wrote:
> Shaohua Li wrote:
> > CPU hotremove will migrate tasks and redirect interrupts off dead cpu.
> > To remove multiple CPUs, we should iteratively do single cpu removal.
> > If tasks and interrupts are migrated to a cpu which will be soon
> > removed, then we will trash tasks and interrupts again. The following
> > patches allow remove several cpus one time. It's fast and avoids
> > unnecessary repeated trash tasks and interrupts. This will help NUMA
> > style hardware removal and SMP suspend/resume. Comments and suggestions
> > are appreciated.
> 
> Some quantification of the benefits of adding this complexity would be
> appreciated.  Like, how long does it take to offline all the cpus in a
> node serially, and how much faster is the bulk method?
This depends on the workload and I haven't a data at hand, sorry. Fast
(less tasks/timers/softirqs migration) is one benefit. The method also
means less time in stop_machine_run and less interrupt redirection, so
smaller impact to the whole system.

Thanks,
Shaohua
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