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SubjectRe: [PATCH 2/2] mm: memcg: add a new MEMCG_UPDATE_BATCH
Feng Tang writes:
>One further thought is, there are quite some "BATCH" number in
>kernel for perf-cpu/global data updating, maybe we can add a
>global flag 'sysctl_need_accurate_stats' for
> if (sysctl_need_accurate_stats)
> batch = SMALLER_BATCH
> else
> batch = BIGGER_BATCH

Moving decisions like this to the system administrator is not really a solution
to the problem -- inclusion should at least be contingent on either having
"correct-ish" stats exported to userspace. Displaying broken stats to the user
-- even with a configuration knob -- is less than ideal and is likely to
confuse and confound issues in future.

I would also like to see numbers from more real-world workloads.
MEMCG_CHARGE_BATCH is certainly fairly arbitrary as-is, but if it is going to
be changed, the reason for that change and its implications (positive and
negative) for real-world workloads must be well understood, and I'm not sure
we're there yet.

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