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SubjectRe: [PATCH] specific do_timer_cpu value for nohz off mode
On Tue, 8 Nov 2011, Dimitri Sivanich wrote:
>
> Allow manual override of the tick_do_timer_cpu.
>
> While not necessarily harmful, doing jiffies updates on an application cpu
> does cause some extra overhead that HPC benchmarking people notice. They
> prefer to have OS activity isolated to certain cpus. They like reproducibility
> of results, and having jiffies updates bouncing around introduces variability.

I really wonder about this changelog. The only case where jiffies
updates bounces around is the NOHZ case. In all other modes (periodic
or highres) the boot cpu gets the do_timer() duty and it's never
assigned to any other cpu.

So what's the point of this exercise? Moving it away from CPU0 for
acedemic reasons or what?

Thanks,

tglx




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