linux-kernel - Re: [PATCH 00/10] mm: Linux VM Infrastructure to support Memory Power Management

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Message-ID: <20110610165529.GC2230@linux.vnet.ibm.com>
Date:	Fri, 10 Jun 2011 09:55:29 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	Kyungmin Park <kmpark@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ankita Garg <ankita@...ibm.com>,
	linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	svaidy@...ux.vnet.ibm.com, thomas.abraham@...aro.org
Subject: Re: [PATCH 00/10] mm: Linux VM Infrastructure to support Memory
 Power Management

On Fri, Jun 10, 2011 at 04:59:54PM +0100, Matthew Garrett wrote:
> On Fri, Jun 10, 2011 at 08:11:21AM -0700, Paul E. McKenney wrote:
> 
> > Of course, on a server, you could get similar results by having a very
> > large amount of memory (say 256GB) and a workload that needed all the
> > memory only occasionally for short periods, but could get by with much
> > less (say 8GB) the rest of the time.  I have no idea whether or not
> > anyone actually has such a system.
> 
> For the server case, the low hanging fruit would seem to be 
> finer-grained self-refresh. At best we seem to be able to do that on a 
> per-CPU socket basis right now. The difference between active and 
> self-refresh would seem to be much larger than the difference between 
> self-refresh and powered down.

By "finer-grained self-refresh" you mean turning off refresh for banks
of memory that are not being used, right?  If so, this is supported by
the memory-regions support provided, at least assuming that the regions
can be aligned with the self-refresh boundaries.

Or am I missing your point?

							Thanx, Paul
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