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

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Message-ID: <9a439cbd-6bdc-3c7b-0327-df3b60cdeff8@suse.cz>
Date:	Thu, 23 Jun 2016 16:06:09 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Mel Gorman <mgorman@...hsingularity.net>,
	Michal Hocko <mhocko@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>, Rik van Riel <riel@...riel.com>,
	Johannes Weiner <hannes@...xchg.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 19/27] mm: Move vmscan writes and file write accounting to
 the node

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...