Re: [patch 10/10] mm: workingset: keep shadow entries in check

[Peter Zijlstra]

On Thu, May 30, 2013 at 02:04:06PM -0400, Johannes Weiner wrote:
> Previously, page cache radix tree nodes were freed after reclaim
> emptied out their page pointers.  But now reclaim stores shadow
> entries in their place, which are only reclaimed when the inodes
> themselves are reclaimed.  This is problematic for bigger files that
> are still in use after they have a significant amount of their cache
> reclaimed, without any of those pages actually refaulting.  The shadow
> entries will just sit there and waste memory.  In the worst case, the
> shadow entries will accumulate until the machine runs out of memory.
> 

Can't we simply prune all refault entries that have a distance larger
than the memory size? Then we must assume that no refault entry means
its too old, which I think is a fair assumption.

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