Re: [PATCH 19/27] mm: Move vmscan writes and file write accounting to the node

[Vlastimil Babka]

On 06/23/2016 03:57 PM, Mel Gorman wrote:
> On Wed, Jun 22, 2016 at 04:40:39PM +0200, Michal Hocko wrote:
> > On Tue 21-06-16 15:15:58, Mel Gorman wrote:
> > > As reclaim is now node-based, it follows that page write activity
> > > due to page reclaim should also be accounted for on the node. For
> > > consistency, also account page writes and page dirtying on a per-node
> > > basis.
> > >
> > > After this patch, there are a few remaining zone counters that may
> > > appear strange but are fine. NUMA stats are still per-zone as this is a
> > > user-space interface that tools consume. NR_MLOCK, NR_SLAB_*, NR_PAGETABLE,
> > > NR_KERNEL_STACK and NR_BOUNCE are all allocations that potentially pin
> > > low memory and cannot trivially be reclaimed on demand. This information
> > > is still useful for debugging a page allocation failure warning.
> >
> > As I've said in other patch. I think we will need to provide
> > /proc/nodeinfo to fill the gap.
>
> I added a patch on top that prints the node stats in zoneinfo but only
> once for the first populated zone in a node. Doing this or creating a
> new file are both potentially surprising but extending zoneinfo means
> there is a greater chance that a user will spot the change.

BTW, there should already be /sys/devices/system/node/nodeX/vmstat 
providing the per-node stats, right?

Changing zoneinfo so that some zones have some stats that others don't 
seems to me like it can break some scripts...