Re: [RESEND PATCH 1/2 -mm] mm: account lazy free pages separately

[Yang Shi]

On 8/14/19 5:49 AM, Vlastimil Babka wrote:
> On 8/9/19 8:26 PM, Yang Shi wrote:
> > Here the new counter is introduced for patch 2/2 to account deferred
> > split THPs into available memory since NR_ANON_THPS may contain
> > non-deferred split THPs.
> >
> > I could use an internal counter for deferred split THPs, but if it is
> > accounted by mod_node_page_state, why not just show it in /proc/meminfo?
> The answer to "Why not" is that it becomes part of userspace API (btw this
> patchset should have CC'd linux-api@ - please do for further iterations) and
> even if the implementation detail of deferred splitting might change in the
> future, we'll basically have to keep the counter (even with 0 value) in
> /proc/meminfo forever.
>
> Also, quite recently we have added the following counter:
>
> KReclaimable: Kernel allocations that the kernel will attempt to reclaim
>                under memory pressure. Includes SReclaimable (below), and other
>                direct allocations with a shrinker.
>
> Although THP allocations are not exactly "kernel allocations", once they are
> unmapped, they are in fact kernel-only, so IMHO it wouldn't be a big stretch to
> add the lazy THP pages there?

Thanks a lot for the suggestion. I agree it may be a good fit. Hope 
"kernel allocations" not cause confusion. But, we can explain in the 
documentation.

> > Or we fix NR_ANON_THPS and show deferred split THPs in /proc/meminfo?