linux-ext4 - RE: [PATCH V2 0/7] Cleancache (was Transcendent Memory): overview

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Message-ID: <312cfff6-7ee7-4a6e-a3fd-fc9b6893f0b1@default>
Date:	Wed, 2 Jun 2010 08:35:43 -0700 (PDT)
From:	Dan Magenheimer <dan.magenheimer@...cle.com>
To:	Jamie Lokier <jamie@...reable.org>
Cc:	chris.mason@...cle.com, viro@...iv.linux.org.uk,
	akpm@...ux-foundation.org, adilger@....com, tytso@....edu,
	mfasheh@...e.com, joel.becker@...cle.com, matthew@....cx,
	linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
	ocfs2-devel@....oracle.com, linux-mm@...ck.org, ngupta@...are.org,
	jeremy@...p.org, JBeulich@...ell.com, kurt.hackel@...cle.com,
	npiggin@...e.de, dave.mccracken@...cle.com, riel@...hat.com,
	avi@...hat.com, konrad.wilk@...cle.com
Subject: RE: [PATCH V2 0/7] Cleancache (was Transcendent Memory): overview

> From: Jamie Lokier [mailto:jamie@...reable.org]
> 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
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