Re: [PATCH] mm, vmscan: do not count freed pages as PGDEACTIVATE

[Johannes Weiner]

On Thu, Jan 12, 2017 at 10:12:21PM +0100, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
> 
> PGDEACTIVATE represents the number of pages moved from the active list
> to the inactive list. At least this sounds like the original motivation
> of the counter. move_active_pages_to_lru, however, counts pages which
> got freed in the mean time as deactivated as well. This is a very rare
> event and counting them as deactivation in itself is not harmful but it
> makes the code more convoluted than necessary - we have to count both
> all pages and those which are freed which is a bit confusing.
> 
> After this patch the PGDEACTIVATE should have a slightly more clear
> semantic and only count those pages which are moved from the active to
> the inactive list which is a plus.
> 
> Suggested-by: Vlastimil Babka <vbabka@xxxxxxx>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>

I bet it's a small inaccuracy in practice, but now that the trace
patches added a proper counter, might as well consolidate into the
correct one.

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>