Re: [PATCH 12/13] mm: numa: Scan pages with elevated page_mapcount

[Peter Zijlstra]

On Wed, Jul 03, 2013 at 03:21:39PM +0100, Mel Gorman wrote:
> Initial support for automatic NUMA balancing was unable to distinguish
> between false shared versus private pages except by ignoring pages with an
> elevated page_mapcount entirely. This patch kicks away the training wheels
> as initial support for identifying shared/private pages is now in place.
> Note that the patch still leaves shared, file-backed in VM_EXEC vmas in
> place guessing that these are shared library pages. Migrating them are
> likely to be of major benefit as generally the expectation would be that
> these are read-shared between caches and that iTLB and iCache pressure is
> generally low.

This reminds me; there a clause in task_numa_work() that skips 'small' VMAs. I
don't see the point of that.

In fact; when using things like electric fence this might mean skipping most
memory.
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