On Tue, Feb 16, 2016 at 02:58:04AM +0000, Nag Avadhanam (nag) wrote:

Its the calculation of the # of bytes of non-reclaimable file system cache
pages that has been troubling us. We do not want to count inactive file
pages (of programs/binaries) that were once mapped by any process in the
system as reclaimable because that might lead to thrashing under memory
pressure (we want to alert admins before system starts dropping text
pages).

The code presented does not match your requirements. It only counts
pages that are currently mapped into ptes. hence it will tell you
that once-used and now unmapped binary pages are reclaimable, and
drop caches will reclaim them. hence they'll need to be fetched from
disk again if they are faulted in again after a drop_caches run.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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