| Message ID | 9b006866-5a8e-dc05-d603-bfe8eb02eef2@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
On Thu, 25 May 2017 12:37:40 -0500 Michael Bringmann <mwb@linux.vnet.ibm.com> wrote: > Removing or adding memory via the PowerPC hotplug interface shows > anomalies in the association between memory and nodes. The code > was updated to ensure that all nodes found at boot are still available > to subsequent DLPAR hotplug-memory operations, even if they are not > needed at boot time. > > Signed-off-by: Michael Bringmann <mwb@linux.vnet.ibm.com> > --- > Changes in V2: > -- Simplify patches to ensure more nodes in possible map, removing > code from PowerPC numa.c that constrained possible map to size > of online map. > --- > arch/powerpc/mm/numa.c | 7 ------- > 1 file changed, 7 deletions(-) > > diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c > index 15c2dd5..18f3038 100644 > --- a/arch/powerpc/mm/numa.c > +++ b/arch/powerpc/mm/numa.c > @@ -907,13 +907,6 @@ void __init initmem_init(void) > > memblock_dump_all(); > > - /* > - * Reduce the possible NUMA nodes to the online NUMA nodes, > - * since we do not support node hotplug. This ensures that we > - * lower the maximum NUMA node ID to what is actually present. > - */ > - nodes_and(node_possible_map, node_possible_map, node_online_map); > - There is an overhead with turning this off if you have too many cgroups with the memory controller. I think this fix was added for a pathological test case. On my system I see 84 cgroups with 1 node, so the probable overhead is 84*255*sizeof(struct mem_cgroup_tree_per_node). I tried some patches to reduce the overhead, but those need more overhauling and rework. Balbir Singh.
Michael Bringmann <mwb@linux.vnet.ibm.com> writes: > Removing or adding memory via the PowerPC hotplug interface shows > anomalies in the association between memory and nodes. What anomalies? Please describe the actual problem you're seeing, with details, and why you think this is the correct fix. This is a revert of 3af229f2071f ("powerpc/numa: Reset node_possible_map to only node_online_map"), so please explain why all the things mentioned in the change log for that commit are either wrong or no longer true. cheers
>> arch/powerpc/mm/numa.c | 7 ------- >> 1 file changed, 7 deletions(-) >> >> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c >> index 15c2dd5..18f3038 100644 >> --- a/arch/powerpc/mm/numa.c >> +++ b/arch/powerpc/mm/numa.c >> @@ -907,13 +907,6 @@ void __init initmem_init(void) >> >> memblock_dump_all(); >> >> - /* >> - * Reduce the possible NUMA nodes to the online NUMA nodes, >> - * since we do not support node hotplug. This ensures that we >> - * lower the maximum NUMA node ID to what is actually present. >> - */ >> - nodes_and(node_possible_map, node_possible_map, node_online_map); >> - > > There is an overhead with turning this off if you have too many cgroups > with the memory controller. I think this fix was added for a pathological > test case. On my system I see 84 cgroups with 1 node, so the probable > overhead is 84*255*sizeof(struct mem_cgroup_tree_per_node). > > I tried some patches to reduce the overhead, but those need more overhauling > and rework. Is there some other way to add a node to a dynamic, running system without crashing? I have not encountered one as yet. > Balbir Singh.
diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c index 15c2dd5..18f3038 100644 --- a/arch/powerpc/mm/numa.c +++ b/arch/powerpc/mm/numa.c @@ -907,13 +907,6 @@ void __init initmem_init(void) memblock_dump_all(); - /* - * Reduce the possible NUMA nodes to the online NUMA nodes, - * since we do not support node hotplug. This ensures that we - * lower the maximum NUMA node ID to what is actually present. - */ - nodes_and(node_possible_map, node_possible_map, node_online_map); - for_each_online_node(nid) { unsigned long start_pfn, end_pfn;
Removing or adding memory via the PowerPC hotplug interface shows anomalies in the association between memory and nodes. The code was updated to ensure that all nodes found at boot are still available to subsequent DLPAR hotplug-memory operations, even if they are not needed at boot time. Signed-off-by: Michael Bringmann <mwb@linux.vnet.ibm.com> --- Changes in V2: -- Simplify patches to ensure more nodes in possible map, removing code from PowerPC numa.c that constrained possible map to size of online map. --- arch/powerpc/mm/numa.c | 7 ------- 1 file changed, 7 deletions(-)