It appears that newly cached entries have their body files remain in dirty "mapped file" VM entries until the file is closed. With a little msync() magic we can turn this dirty memory clean.
Created attachment 261747 [details] Patch idea
Comment on attachment 261747 [details] Patch idea Clearing flags on attachment: 261747 Committed r190121: <http://trac.webkit.org/changeset/190121>
All reviewed patches have been landed. Closing bug.