Re: [patch v2] mm, vmstat: print non-populated zones in zoneinfo

[Michal Hocko]

On Wed 08-03-17 15:41:59, Michal Hocko wrote:
> On Fri 03-03-17 14:53:07, David Rientjes wrote:
> > Initscripts can use the information (protection levels) from
> > /proc/zoneinfo to configure vm.lowmem_reserve_ratio at boot.
> > 
> > vm.lowmem_reserve_ratio is an array of ratios for each configured zone on
> > the system.  If a zone is not populated on an arch, /proc/zoneinfo
> > suppresses its output.
> > 
> > This results in there not being a 1:1 mapping between the set of zones
> > emitted by /proc/zoneinfo and the zones configured by
> > vm.lowmem_reserve_ratio.
> >
> > This patch shows statistics for non-populated zones in /proc/zoneinfo.
> > The zones exist and hold a spot in the vm.lowmem_reserve_ratio array.
> > Without this patch, it is not possible to determine which index in the
> > array controls which zone if one or more zones on the system are not
> > populated.
> > 
> > Remaining users of walk_zones_in_node() are unchanged.  Files such as
> > /proc/pagetypeinfo require certain zone data to be initialized properly
> > for display, which is not done for unpopulated zones.
> 
> Does it really make sense to print any counters of that zone though?
> Your follow up patch just suggests that we don't want some but what
> about others?
> 
> I can see how skipping empty zones completely can be clumsy but wouldn't
> it be sufficient to just provide
> 
> Node $NUM, zone $NAME
> (unpopulated)
> 
> instead?

ping
-- 
Michal Hocko
SUSE Labs