Re: [PATCH] mm/vmstat: retrieve more accurate vmstat value

From: Michal Hocko
Date: Wed Nov 25 2015 - 13:03:56 EST


On Wed 25-11-15 10:04:44, Christoph Lameter wrote:
> On Wed, 25 Nov 2015, Joonsoo Kim wrote:
>
> > I think that maintaining duplicate counter to guarantee accuracy isn't
> > reasonable solution. It would cause more overhead to the system.
>
> Simply remove the counter from the vmstat handling and do it differently
> then.

We definitely do not want yet another set of counters. vmstat counters
are not only to be exported into the userspace. We have in kernel users
as well. I do agree that there are users who can cope with some level of
imprecision though and those which depend on the accuracy can use
zone_page_state_snapshot which doesn't impose any overhead on others.
[...]
--
Michal Hocko
SUSE Labs
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