linux-kernel - Re: [PATCH 02/10] staging: zcache: remove zcache

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Message-ID: <20130411200518.GA5268@kroah.com>
Date:	Thu, 11 Apr 2013 13:05:18 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Dan Magenheimer <dan.magenheimer@...cle.com>
Cc:	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Seth Jennings <sjenning@...ux.vnet.ibm.com>,
	Konrad Rzeszutek Wilk <konrad@...nok.org>,
	Minchan Kim <minchan@...nel.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Bob Liu <bob.liu@...cle.com>
Subject: Re: [PATCH 02/10] staging: zcache: remove zcache_freeze

On Thu, Apr 11, 2013 at 10:13:42AM -0700, Dan Magenheimer wrote:
> > From: Wanpeng Li [mailto:liwanp@...ux.vnet.ibm.com]
> > Subject: [PATCH 02/10] staging: zcache: remove zcache_freeze
> > 
> > The default value of zcache_freeze is false and it won't be modified by
> > other codes. Remove zcache_freeze since no routine can disable zcache
> > during system running.
> > 
> > Signed-off-by: Wanpeng Li <liwanp@...ux.vnet.ibm.com>
> 
> I'd prefer to leave this code in place as it may be very useful
> if/when zcache becomes more tightly integrated into the MM subsystem
> and the rest of the kernel.  And the subtleties for temporarily disabling
> zcache (which is what zcache_freeze does) are non-obvious and
> may cause data loss so if someone wants to add this functionality
> back in later and don't have this piece of code, it may take
> a lot of pain to get it working.
> 
> Usage example: All CPUs are fully saturated so it is questionable
> whether spending CPU cycles for compression is wise.  Kernel
> could disable zcache using zcache_freeze.  (Yes, a new entry point
> would need to be added to enable/disable zcache_freeze.)
> 
> My two cents... others are welcome to override.

I will not override, and did not take this patch.

greg k-h
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