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
> From: Jamie Lokier [mailto:[email protected]]
> Subject: Re: [PATCH V2 0/7] Cleancache (was Transcendent Memory):
> overview
>
> 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?
No plans yet, though we agree it sounds useful, at least for
apps that bypass the page cache (e.g. O_DIRECT). If you have
time and interest to investigate this further, I'd be happy
to help. Send email offlist.
Thanks,
Dan