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Message-ID: <47B0ACBA.4090207@oracle.com> Date: Mon, 11 Feb 2008 12:14:50 -0800 From: Randy Dunlap <randy.dunlap@...cle.com> To: David Rientjes <rientjes@...gle.com> CC: Andrew Morton <akpm@...ux-foundation.org>, Paul Jackson <pj@....com>, Christoph Lameter <clameter@....com>, Lee Schermerhorn <Lee.Schermerhorn@...com>, Andi Kleen <ak@...e.de>, linux-kernel@...r.kernel.org Subject: Re: [patch 4/4 v2] mempolicy: update NUMA memory policy documentation David Rientjes wrote: > Updates Documentation/vm/numa_memory_policy.txt and > Documentation/filesystems/tmpfs.txt to describe optional mempolicy mode > flags. > > Cc: Paul Jackson <pj@....com> > Cc: Christoph Lameter <clameter@....com> > Cc: Lee Schermerhorn <Lee.Schermerhorn@...com> > Cc: Andi Kleen <ak@...e.de> > Cc: Randy Dunlap <randy.dunlap@...cle.com> > Signed-off-by: David Rientjes <rientjes@...gle.com> Acked-by: Randy Dunlap <randy.dunlap@...cle.com> Thanks. > --- > Includes fixes to problems identified by Randy Dunlap. > > Documentation/filesystems/tmpfs.txt | 11 ++++++++ > Documentation/vm/numa_memory_policy.txt | 41 +++++++++++++++++++++++++++---- > 2 files changed, 47 insertions(+), 5 deletions(-) > > diff --git a/Documentation/filesystems/tmpfs.txt b/Documentation/filesystems/tmpfs.txt > --- a/Documentation/filesystems/tmpfs.txt > +++ b/Documentation/filesystems/tmpfs.txt > @@ -92,6 +92,17 @@ NodeList format is a comma-separated list of decimal numbers and ranges, > a range being two hyphen-separated decimal numbers, the smallest and > largest node numbers in the range. For example, mpol=bind:0-3,5,7,9-15 > > +It is possible to specify a static NodeList by appending '=static' to > +the memory policy mode in the mpol= argument. This will require that > +tasks or VMA's restricted to a subset of allowed nodes are only allowed > +to effect the memory policy over those nodes. No remapping of the > +NodeList when the policy is rebound, which is the default behavior, is > +allowed when '=static' is specified. For example: > + > +mpol=bind=static:NodeList will only allocate from each node in > + the NodeList without remapping the > + NodeList if the policy is rebound > + > Note that trying to mount a tmpfs with an mpol option will fail if the > running kernel does not support NUMA; and will fail if its nodelist > specifies a node which is not online. If your system relies on that > 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 > @@ -135,9 +135,11 @@ most general to most specific: > > Components of Memory Policies > > - A Linux memory policy is a tuple consisting of a "mode" and an optional set > - of nodes. The mode determine the behavior of the policy, while the > - optional set of nodes can be viewed as the arguments to the behavior. > + A Linux memory policy consists of a "mode", optional mode flags, and an > + optional set of nodes. The mode determines the behavior of the policy, > + the optional mode flags determine the behavior of the mode, and the > + optional set of nodes can be viewed as the arguments to the policy > + behavior. > > Internally, memory policies are implemented by a reference counted > structure, struct mempolicy. Details of this structure will be discussed > @@ -145,7 +147,12 @@ Components of Memory Policies > > Note: in some functions AND in the struct mempolicy itself, the mode > is called "policy". However, to avoid confusion with the policy tuple, > - this document will continue to use the term "mode". > + this document will continue to use the term "mode". Since the mode and > + optional mode flags are stored in the same struct mempolicy member > + (specifically, pol->policy), you must use mpol_mode(pol->policy) to > + access only the mode and mpol_flags(pol->policy) to access only the > + flags. Any function with a formal of type enum mempolicy_mode only > + refers to the mode. > > Linux memory policy supports the following 4 behavioral modes: > > @@ -231,6 +238,28 @@ Components of Memory Policies > the temporary interleaved system default policy works in this > mode. > > + Linux memory policy supports the following optional mode flag: > + > + 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 accessible > + 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 accessible nodes, the node (Preferred) or > + nodemask (Bind, Interleave) is remapped to the new set of > + accessible nodes. This may result in nodes being used that were > + previously undesired. With this flag, the policy is either > + effected over the user's specified nodemask or the Default > + behavior 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 accessible from the user's nodemask, the "interleave" > + only occurs over that node. If no nodes from the user's > + nodemask are now accessible, the Default behavior is used. > + > MEMORY POLICY APIs > > Linux supports 3 system calls for controlling memory policy. These APIS > @@ -251,7 +280,9 @@ Set [Task] Memory Policy: > Set's the calling task's "task/process memory policy" to mode > specified by the 'mode' argument and the set of nodes defined > by 'nmask'. 'nmask' points to a bit mask of node ids containing > - at least 'maxnode' ids. > + at least 'maxnode' ids. Optional mode flags may be passed by > + combining the 'mode' argument with the flag (for example: > + MPOL_INTERLEAVE | MPOL_F_STATIC_NODES). > > See the set_mempolicy(2) man page for more details > -- ~Randy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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