linux-kernel - Re: [patch 6/6] mempolicy: update NUMA memory policy documentation

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Message-Id: <20080226113441.934c8c90.pj@sgi.com>
Date:	Tue, 26 Feb 2008 11:34:41 -0600
From:	Paul Jackson <pj@....com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	akpm@...ux-foundation.org, clameter@....com,
	Lee.Schermerhorn@...com, ak@...e.de, randy.dunlap@...cle.com,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 6/6] mempolicy: update NUMA memory policy documentation

+	MPOL_F_RELATIVE_NODES:  This flag specifies that the nodemask passed
+	by the user should remain in the same context as it is for the
+	current task or VMA's set of accessible nodes after the memory
+	policy has been defined.
+
+	    Without this flag (and without MPOL_F_STATIC_NODES), anytime a
+	    mempolicy is rebound because of a change in the set of
+	    accessible nodes, the node (Preferred) or nodemask (Bind,
+	    Interleave) is remapped to the new set of accessible nodes.
+	    With this flag, the remap is done to ensure the context of the
+	    previous nodemask with its set of allowed mems is preserved.

Hmmm ... I've read this several times now ... still can't figure out
what it's saying ;).  And it doesn't really explain key aspects of
MPOL_F_RELATIVE_NODES, such as that it provides cpuset relative
numbering (use nodes 0..N-1, regardless of your current cpuset, to
refer to the first N nodes in whatever is your current cpuset.)

Perhaps we'd be further ahead of the game if you started with the
documentation changes to Documentation/vm/numa_memory_policy.txt,
in my patch:
	Date: Sun, 23 Dec 2007 22:24:02 -0600
	From: Paul Jackson <pj@....com>
	To: David Rientjes <rientjes@...gle.com>
	Cc: Lee.Schermerhorn@...com, clameter@....com
	Subject: Re: [RFC] cpuset relative memory policies - second choice
	Message-Id: <20071223222402.5486bf0a.pj@....com>

Change MPOL_MASK_REL to MPOL_F_RELATIVE_NODES and similar changes.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@....com> 1.940.382.4214
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