On Thu, 2009-10-01 at 12:47 -0700, Randy Dunlap wrote: > On Thu, 01 Oct 2009 12:58:51 -0400 Lee Schermerhorn wrote: > > > [PATCH 7/10] hugetlb: update hugetlb documentation for NUMA controls > > > > Against: 2.6.31-mmotm-090925-1435 > > > > > > This patch updates the kernel huge tlb documentation to describe the > > numa memory policy based huge page management. Additionaly, the patch > > includes a fair amount of rework to improve consistency, eliminate > > duplication and set the context for documenting the memory policy > > interaction. > > > > Signed-off-by: Lee Schermerhorn <lee.schermerhorn@xxxxxx> > > Acked-by: David Rientjes <rientjes@xxxxxxxxxx> > > Acked-by: Mel Gorman <mel@xxxxxxxxx> > > > > Documentation/vm/hugetlbpage.txt | 267 ++++++++++++++++++++++++++------------- > > 1 file changed, 179 insertions(+), 88 deletions(-) > > > > Index: linux-2.6.31-mmotm-090925-1435/Documentation/vm/hugetlbpage.txt > > =================================================================== > > --- linux-2.6.31-mmotm-090925-1435.orig/Documentation/vm/hugetlbpage.txt 2009-09-30 15:04:40.000000000 -0400 > > +++ linux-2.6.31-mmotm-090925-1435/Documentation/vm/hugetlbpage.txt 2009-09-30 15:05:22.000000000 -0400 > > @@ -159,6 +163,101 @@ Inside each of these directories, the sa > > > > which function as described above for the default huge page-sized case. > > > > + > > +Interaction of Task Memory Policy with Huge Page Allocation/Freeing: > > Preferable not to end section "title" with a colon. Thanks for the quick review, Randy. I'll fix these in an incremental or respun patch. Lee > > > + > > +Whether huge pages are allocated and freed via the /proc interface or > > +the /sysfs interface using the nr_hugepages_mempolicy attribute, the NUMA > > +nodes from which huge pages are allocated or freed are controlled by the > > +NUMA memory policy of the task that modifies the nr_hugepages_mempolicy > > +sysctl or attribute. When the nr_hugepages attribute is used, mempolicy > > +is ignored > > ignored. > > > + > > +The recommended method to allocate or free huge pages to/from the kernel > > +huge page pool, using the nr_hugepages example above, is: > > + > > + numactl --interleave <node-list> echo 20 \ > > + >/proc/sys/vm/nr_hugepages_mempolicy > > + > > +or, more succinctly: > > + > > + numactl -m <node-list> echo 20 >/proc/sys/vm/nr_hugepages_mempolicy > > + > > +This will allocate or free abs(20 - nr_hugepages) to or from the nodes > > +specified in <node-list>, depending on whether number of persistent huge pages > > +is initially less than or greater than 20, respectively. No huge pages will be > > +allocated nor freed on any node not included in the specified <node-list>. > > + > > +When adjusting the persistent hugepage count via nr_hugepages_mempolicy, any > > +memory policy mode--bind, preferred, local or interleave--may be used. The > > +resulting effect on persistent huge page allocation is as follows: > > + > ... > > + > > +Per Node Hugepages Attributes > > + > > +A subset of the contents of the root huge page control directory in sysfs, > > +described above, has been replicated under each "node" system device in: > > + > > + /sys/devices/system/node/node[0-9]*/hugepages/ > > + > > +Under this directory, the subdirectory for each supported huge page size > > +contains the following attribute files: > > + > > + nr_hugepages > > + free_hugepages > > + surplus_hugepages > > + > > +The free_' and surplus_' attribute files are read-only. They return the number > > +of free and surplus [overcommitted] huge pages, respectively, on the parent > > +node. > > + > > +The nr_hugepages attribute will return the total number of huge pages on the > > s/will return/returns/ [just a preference] > > > +specified node. When this attribute is written, the number of persistent huge > > +pages on the parent node will be adjusted to the specified value, if sufficient > > +resources exist, regardless of the task's mempolicy or cpuset constraints. > > + > > +Note that the number of overcommit and reserve pages remain global quantities, > > +as we don't know until fault time, when the faulting task's mempolicy is > > +applied, from which node the huge page allocation will be attempted. > > + > > + > > +Using Huge Pages: > > Drop ':'. > > > + > > If the user applications are going to request huge pages using mmap system > > call, then it is required that system administrator mount a file system of > > type hugetlbfs: > > > --- > ~Randy -- To unsubscribe from this list: send the line "unsubscribe linux-numa" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
