Dan Magenheimer wrote:

Most important, cleancache is "ephemeral".  Pages which are copied into
cleancache have an indefinite lifetime which is completely unknowable
by the kernel and so may or may not still be in cleancache at any later time.
Thus, as its name implies, cleancache is not suitable for dirty pages.  The
pseudo-RAM has complete discretion over what pages to preserve and what
pages to discard and when.

Fwiw, the feature sounds useful to userspace too, for those things
with memory hungry caches like web browsers.  Any plans to make it
available to userspace?

Thanks,
-- Jamie