Re: [PATCH 2/2] mm: memcg: add a new MEMCG_UPDATE_BATCH

[Chris Down]

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.