Re: [PATCH 1/3] mm, sysctl: make VM stats configurable

[Michal Hocko]

On Mon 18-09-17 11:22:37, kemi wrote:
> 
> 
> On 2017å09æ15æ 19:49, Michal Hocko wrote:
> > On Fri 15-09-17 17:23:24, Kemi Wang wrote:
> >> This patch adds a tunable interface that allows VM stats configurable, as
> >> suggested by Dave Hansen and Ying Huang.
> >>
> >> When performance becomes a bottleneck and you can tolerate some possible
> >> tool breakage and some decreased counter precision (e.g. numa counter), you
> >> can do:
> >> 	echo [C|c]oarse > /proc/sys/vm/vmstat_mode
> >>
> >> When performance is not a bottleneck and you want all tooling to work, you
> >> can do:
> >> 	echo [S|s]trict > /proc/sys/vm/vmstat_mode
> >>
> >> We recommend automatic detection of virtual memory statistics by system,
> >> this is also system default configuration, you can do:
> >> 	echo [A|a]uto > /proc/sys/vm/vmstat_mode
> >>
> >> The next patch handles numa statistics distinctively based-on different VM
> >> stats mode.
> > 
> > I would just merge this with the second patch so that it is clear how
> > those modes are implemented. I am also wondering why cannot we have a
> > much simpler interface and implementation to enable/disable numa stats
> > (btw. sysctl_vm_numa_stats would be more descriptive IMHO).
> > 
> 
> Apologize for resending it, because I found my previous reply mixed with
> Michal's in many email client.
> 
> The motivation is that we propose a general tunable  interface for VM stats.
> This would be more scalable, since we don't have to add an individual
> Interface for each type of counter that can be configurable.

Can you envision which other counters would fall into the same category?

> In the second patch, NUMA stats, as an example, can benefit for that.
> If you still hold your idea, I don't mind to merge them together.

Well, I would prefer simplicy in the first place.
-- 
Michal Hocko
SUSE Labs