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SubjectRe: [RESEND PATCH 1/2 -mm] mm: account lazy free pages separately
On Wed 14-08-19 14:49:18, 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?

That would indeed fit in much better than a dedicated counter.
--
Michal Hocko
SUSE Labs

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