Messages in this thread | | | From | Andi Kleen <> | Subject | Re: [PATCH 1/2] mm: NUMA stats code cleanup and enhancement | Date | Tue, 28 Nov 2017 10:40:52 -0800 |
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Vlastimil Babka <vbabka@suse.cz> writes: > > I'm worried about the "for_each_possible..." approach here and elsewhere > in the patch as it can be rather excessive compared to the online number > of cpus (we've seen BIOSes report large numbers of possible CPU's). IIRC
Even if they report a few hundred extra reading some more shared cache lines is very cheap. The prefetcher usually quickly figures out such a pattern and reads it all in parallel.
I doubt it will be noticeable, especially not in a slow path like reading something from proc/sys.
> the general approach with vmstat is to query just online cpu's / nodes, > and if they go offline, transfer their accumulated stats to some other > "victim"?
That's very complicated, and unlikely to be worth it.
-Andi
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