linux-kernel - Re: [PATCH 0/8] zcache: page cache compression support

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Date:	Thu, 22 Jul 2010 14:00:05 -0700
From:	Greg KH <greg@...ah.com>
To:	Dan Magenheimer <dan.magenheimer@...cle.com>
Cc:	Nitin Gupta <ngupta@...are.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, Avi Kivity <avi@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Konrad Wilk <konrad.wilk@...cle.com>,
	linux-mm <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/8] zcache: page cache compression support

On Thu, Jul 22, 2010 at 12:54:57PM -0700, Dan Magenheimer wrote:
> > From: Greg KH [mailto:greg@...ah.com]
> > Sent: Thursday, July 22, 2010 1:15 PM
> > To: Nitin Gupta
> > Cc: Pekka Enberg; Hugh Dickins; Andrew Morton; Dan Magenheimer; Rik van
> > Riel; Avi Kivity; Christoph Hellwig; Minchan Kim; Konrad Rzeszutek
> > Wilk; linux-mm; linux-kernel
> > Subject: Re: [PATCH 0/8] zcache: page cache compression support
> > 
> > On Fri, Jul 16, 2010 at 06:07:42PM +0530, Nitin Gupta wrote:
> > > Frequently accessed filesystem data is stored in memory to reduce
> > access to
> > > (much) slower backing disks. Under memory pressure, these pages are
> > freed and
> > > when needed again, they have to be read from disks again. When
> > combined working
> > > set of all running application exceeds amount of physical RAM, we get
> > extereme
> > > slowdown as reading a page from disk can take time in order of
> > milliseconds.
> > 
> > <snip>
> > 
> > Given that there were a lot of comments and changes for this series,
> > can
> > you resend them with your updates so I can then apply them if they are
> > acceptable to everyone?
> > 
> > thanks,
> > greg k-h
> 
> Hi Greg --
> 
> Nitin's zcache code is dependent on the cleancache series:
> http://lkml.org/lkml/2010/6/21/411 

Ah, I didn't realize that.  Hm, that makes it something that I can't
take until that code is upstream, sorry.

> The cleancache series has not changed since V3 (other than
> fixing a couple of documentation typos) and didn't receive any
> comments other than Christoph's concern that there weren't
> any users... which I think has been since addressed with the
> posting of the Xen tmem driver code and Nitin's zcache.
> 
> If you are ready to apply the cleancache series, great!
> If not, please let me know next steps so cleancache isn't
> an impediment for applying the zcache series.

I don't know, work with the kernel developers to resolve the issues they
pointed out in the cleancache code and when it goes in, then I can take
these patches.

good luck,

greg k-h
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