Messages in this thread Patch in this message | | | Subject | [PATCH] 2.6.25-rc3-mm1 - Mempolicy - update stale documentation and comments | From | Lee Schermerhorn <> | Date | Tue, 04 Mar 2008 15:20:56 -0500 |
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Was Re: [PATCH 5/6] Filter based on a nodemask as well as a gfp_mask
On Thu, 2008-02-28 at 23:01 -0600, Paul Jackson wrote: > Mel wrote: > > A positive benefit of > > this is that allocations using MPOL_BIND now use the local-node-ordered > > zonelist instead of a custom node-id-ordered zonelist. > > Could you update the now obsolete documentation (perhaps just delete > the no longer correct remark): > > Documentation/vm/numa_memory_policy.txt: > > MPOL_BIND: This mode specifies that memory must come from the > set of nodes specified by the policy. > > The memory policy APIs do not specify an order in which the nodes > will be searched. However, unlike "local allocation", the Bind > policy does not consider the distance between the nodes. Rather, > allocations will fallback to the nodes specified by the policy in > order of numeric node id. Like everything in Linux, this is subject > to change. >
How's this:
PATCH Mempolicy: update documentation and comments
Address stale comments and numa_memory_policy.txt discussion based on Mel Gorman's changes to page allocation zonelist handling.
Specifically: mpol_free() and mpol_copy() no longer need to deal with a custom zonelist for MPOL_BIND policy, and MPOL_BIND now allocates memory from the nearest node with available memory in the specified nodemask.
In "fixing" the mpol_free() and mpol_copy() comments in mempolicy.h, I wanted to replace them with something, rather than just deleting them. So, I described the reference counting. Not directly related to the zonelist changes, but useful, IMO.
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Documentation/vm/numa_memory_policy.txt | 11 +++-------- include/linux/mempolicy.h | 8 +++++--- 2 files changed, 8 insertions(+), 11 deletions(-)
Index: linux-2.6.25-rc3-mm1/Documentation/vm/numa_memory_policy.txt =================================================================== --- linux-2.6.25-rc3-mm1.orig/Documentation/vm/numa_memory_policy.txt 2008-01-24 17:58:37.000000000 -0500 +++ linux-2.6.25-rc3-mm1/Documentation/vm/numa_memory_policy.txt 2008-03-04 14:44:51.000000000 -0500 @@ -182,14 +182,9 @@ Components of Memory Policies The Default mode does not use the optional set of nodes. MPOL_BIND: This mode specifies that memory must come from the - set of nodes specified by the policy. - - The memory policy APIs do not specify an order in which the nodes - will be searched. However, unlike "local allocation", the Bind - policy does not consider the distance between the nodes. Rather, - allocations will fallback to the nodes specified by the policy in - order of numeric node id. Like everything in Linux, this is subject - to change. + set of nodes specified by the policy. Memory will be allocated from + the node in the set with sufficient free memory that is closest to + the node where the allocation takes place. MPOL_PREFERRED: This mode specifies that the allocation should be attempted from the single node specified in the policy. If that Index: linux-2.6.25-rc3-mm1/include/linux/mempolicy.h =================================================================== --- linux-2.6.25-rc3-mm1.orig/include/linux/mempolicy.h 2008-03-04 14:19:06.000000000 -0500 +++ linux-2.6.25-rc3-mm1/include/linux/mempolicy.h 2008-03-04 14:38:29.000000000 -0500 @@ -54,11 +54,13 @@ struct mm_struct; * mmap_sem. * * Freeing policy: - * When policy is MPOL_BIND v.zonelist is kmalloc'ed and must be kfree'd. - * All other policies don't have any external state. mpol_free() handles this. + * Mempolicy objects are reference counted. A mempolicy will be freed when + * mpol_free() decrements the reference count to zero. * * Copying policy objects: - * For MPOL_BIND the zonelist must be always duplicated. mpol_clone() does this. + * mpol_copy() allocates a new mempolicy and copies the specified mempolicy + * to the new storage. The reference count of the new object is initialized + * to 1, representing the caller of mpol_copy(). */ struct mempolicy { atomic_t refcnt;
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