| Message ID | 20210304235951.271553C2@viggo.jf.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Migrate Pages in lieu of discard | expand |
On Thu, Mar 4, 2021 at 4:00 PM Dave Hansen <dave.hansen@linux.intel.com> wrote: > > > From: Dave Hansen <dave.hansen@linux.intel.com> > > Prepare for the kernel to auto-migrate pages to other memory nodes > with a user defined node migration table. This allows creating single > migration target for each NUMA node to enable the kernel to do NUMA > page migrations instead of simply reclaiming colder pages. A node > with no target is a "terminal node", so reclaim acts normally there. > The migration target does not fundamentally _need_ to be a single node, > but this implementation starts there to limit complexity. > > If you consider the migration path as a graph, cycles (loops) in the > graph are disallowed. This avoids wasting resources by constantly > migrating (A->B, B->A, A->B ...). The expectation is that cycles will > never be allowed. Reviewed-by: Yang Shi <shy828301@gmail.com> > > Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> > Cc: Yang Shi <yang.shi@linux.alibaba.com> > Cc: David Rientjes <rientjes@google.com> > Cc: Huang Ying <ying.huang@intel.com> > Cc: Dan Williams <dan.j.williams@intel.com> > Cc: David Hildenbrand <david@redhat.com> > Cc: osalvador <osalvador@suse.de> > > -- > > changes since 20200122: > * Make node_demotion[] __read_mostly > > changes in July 2020: > - Remove loop from next_demotion_node() and get_online_mems(). > This means that the node returned by next_demotion_node() > might now be offline, but the worst case is that the > allocation fails. That's fine since it is transient. > --- > > b/mm/migrate.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff -puN mm/migrate.c~0006-node-Define-and-export-memory-migration-path mm/migrate.c > --- a/mm/migrate.c~0006-node-Define-and-export-memory-migration-path 2021-03-04 15:35:51.353806441 -0800 > +++ b/mm/migrate.c 2021-03-04 15:35:51.359806441 -0800 > @@ -1157,6 +1157,23 @@ out: > return rc; > } > > +static int node_demotion[MAX_NUMNODES] __read_mostly = > + {[0 ... MAX_NUMNODES - 1] = NUMA_NO_NODE}; > + > +/** > + * next_demotion_node() - Get the next node in the demotion path > + * @node: The starting node to lookup the next node > + * > + * @returns: node id for next memory node in the demotion path hierarchy > + * from @node; NUMA_NO_NODE if @node is terminal. This does not keep > + * @node online or guarantee that it *continues* to be the next demotion > + * target. > + */ > +int next_demotion_node(int node) > +{ > + return node_demotion[node]; > +} > + > /* > * Obtain the lock on page, remove all ptes and migrate the page > * to the newly allocated page in newpage. > _ >
diff -puN mm/migrate.c~0006-node-Define-and-export-memory-migration-path mm/migrate.c --- a/mm/migrate.c~0006-node-Define-and-export-memory-migration-path 2021-03-04 15:35:51.353806441 -0800 +++ b/mm/migrate.c 2021-03-04 15:35:51.359806441 -0800 @@ -1157,6 +1157,23 @@ out: return rc; } +static int node_demotion[MAX_NUMNODES] __read_mostly = + {[0 ... MAX_NUMNODES - 1] = NUMA_NO_NODE}; + +/** + * next_demotion_node() - Get the next node in the demotion path + * @node: The starting node to lookup the next node + * + * @returns: node id for next memory node in the demotion path hierarchy + * from @node; NUMA_NO_NODE if @node is terminal. This does not keep + * @node online or guarantee that it *continues* to be the next demotion + * target. + */ +int next_demotion_node(int node) +{ + return node_demotion[node]; +} + /* * Obtain the lock on page, remove all ptes and migrate the page * to the newly allocated page in newpage.