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

[Randy Dunlap]

David Rientjes wrote:
> Updates Documentation/vm/numa_memory_policy.txt and
> Documentation/filesystems/tmpfs.txt to describe optional mempolicy mode
> flags.
>
> Cc: Christoph Lameter <clameter@xxxxxxx>
> Cc: Lee Schermerhorn <Lee.Schermerhorn@xxxxxx>
> Cc: Andi Kleen <ak@xxxxxxx>
> Cc: Randy Dunlap <randy.dunlap@xxxxxxxxxx>
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
> Signed-off-by: Paul Jackson <pj@xxxxxxx>
> ---
>  Documentation/filesystems/tmpfs.txt     |   12 +++
>  Documentation/vm/numa_memory_policy.txt |  131 +++++++++++++++++++++++-------
>  2 files changed, 112 insertions(+), 31 deletions(-)
>
> diff --git a/Documentation/vm/numa_memory_policy.txt b/Documentation/vm/numa_memory_policy.txt
> --- a/Documentation/vm/numa_memory_policy.txt
> +++ b/Documentation/vm/numa_memory_policy.txt

> @@ -231,6 +234,80 @@ Components of Memory Policies
>  	    the temporary interleaved system default policy works in this
>  	    mode.
>  
> +   Linux memory policy supports the following optional mode flag:

                                                              flags:

> +
> +	MPOL_F_STATIC_NODES:  This flag specifies that the nodemask passed by
> +	the user should not be remapped if the task or VMA's set of allowed
> +	nodes changes after the memory policy has been defined.
> +
> +	    Without this flag, anytime a mempolicy is rebound because of a
> +	    change in the set of allowed nodes, the node (Preferred) or
> +	    nodemask (Bind, Interleave) is remapped to the new set of
> +	    allowed nodes.  This may result in nodes being used that were
> +	    previously undesired.
> +
> +	    With this flag, if the user specified nodes overlap with the

                                  user-specified

> +	    nodes allowed by the task's cpuset, then the memory policy is
> +	    applied to their intersection.  If the two sets of nodes do not
> +	    overlap, the Default policy is used.
> +
> +	    For example, consider a task that is attached to a cpuset with
> +	    mems 1-3 that sets an Interleave policy over the same set.  If
> +	    the cpuset's mems change to 3-5, the Interleave will now occur
> +	    over nodes 3, 4, and 5.  With this flag, however, since only node
> +	    3 is allowed from the user's nodemask, the "interleave" only
> +	    occurs over that node.  If no nodes from the user's nodemask are
> +	    now allowed, the Default behavior is used.
> +
> +	    MPOL_F_STATIC_NODES cannot be used with MPOL_F_RELATIVE_NODES.
> +


--
~Randy
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