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

From: Vlastimil Babka
Date: Thu Jun 23 2016 - 10:06:17 EST


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...