Re: [Xen-devel] [RFO] #2: removing a concurrency bottleneck

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

>>> Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> 19.03.09 18:52 >>>
>In per-cpu, I would allocate at system initialization one
>pair of buffers for each cpu (question: num_present_cpus,
>num_online_cpus, or num_possible_cpus?).  Then no lock
>is required.

It should certainly be num_possible_cpus(), which (hopefully) is identical to
num_present_cpus() until physical CPU hotplug gets supported, in which
case some infrastructure will need to be added anyway so that your and
other code could do such per-CPU allocations on demand.

Other than Keir suggested, I'd not recommend adding further NR_CPUS
sized arrays (based mostly on how long it took to mostly (fully?) get rid of
them in Linux in order to support huge systems) - just use per-CPU pointers
to dynamically allocated memory.

Jan


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