On Wed, Jul 28, 2021 at 02:47:23PM +0200, Michal Hocko wrote: > On Mon 12-07-21 16:09:33, Feng Tang wrote: > > From: Ben Widawsky <ben.widawsky@xxxxxxxxx> > > > > Adds a new mode to the existing mempolicy modes, MPOL_PREFERRED_MANY. > > > > MPOL_PREFERRED_MANY will be adequately documented in the internal > > admin-guide with this patch. Eventually, the man pages for mbind(2), > > get_mempolicy(2), set_mempolicy(2) and numactl(8) will also have text > > about this mode. Those shall contain the canonical reference. > > > > NUMA systems continue to become more prevalent. New technologies like > > PMEM make finer grain control over memory access patterns increasingly > > desirable. MPOL_PREFERRED_MANY allows userspace to specify a set of > > nodes that will be tried first when performing allocations. If those > > allocations fail, all remaining nodes will be tried. It's a straight > > forward API which solves many of the presumptive needs of system > > administrators wanting to optimize workloads on such machines. The mode > > will work either per VMA, or per thread. > > > > Link: https://lore.kernel.org/r/20200630212517.308045-13-ben.widawsky@xxxxxxxxx > > Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx> > > Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx> > > --- > > Documentation/admin-guide/mm/numa_memory_policy.rst | 16 ++++++++++++---- > > mm/mempolicy.c | 7 +------ > > 2 files changed, 13 insertions(+), 10 deletions(-) > > > > diff --git a/Documentation/admin-guide/mm/numa_memory_policy.rst b/Documentation/admin-guide/mm/numa_memory_policy.rst > > index 067a90a1499c..cd653561e531 100644 > > --- a/Documentation/admin-guide/mm/numa_memory_policy.rst > > +++ b/Documentation/admin-guide/mm/numa_memory_policy.rst > > @@ -245,6 +245,14 @@ MPOL_INTERLEAVED > > address range or file. During system boot up, the temporary > > interleaved system default policy works in this mode. > > > > +MPOL_PREFERRED_MANY > > + This mode specifies that the allocation should be attempted from the > > + nodemask specified in the policy. If that allocation fails, the kernel > > + will search other nodes, in order of increasing distance from the first > > + set bit in the nodemask based on information provided by the platform > > + firmware. It is similar to MPOL_PREFERRED with the main exception that > > + is an error to have an empty nodemask. > > I believe the target audience of this documents are users rather than > kernel developers and for those the wording might be rather cryptic. I > would rephrase like this > This mode specifices that the allocation should be preferrably > satisfied from the nodemask specified in the policy. If there is > a memory pressure on all nodes in the nodemask the allocation > can fall back to all existing numa nodes. This is effectively > MPOL_PREFERRED allowed for a mask rather than a single node. > > With that or similar feel free to add > Acked-by: Michal Hocko <mhocko@xxxxxxxx> Thanks! Will revise the test as suggested. - Feng > -- > Michal Hocko > SUSE Labs
