Re: [PATCH] kernel: fs: drop_caches: add dds drop_caches_count

[Dave Chinner]

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@xxxxxxxxxxxxx