Re: [PATCH v2 0/3] Updates to powerpc for robust CPU online/offline

On Mon, Aug 23, 2021 at 03:04:37PM +0530, Srikar Dronamraju wrote:

* Peter Zijlstra [off-list ref] [2021-08-23 10:33:30]:

quoted

On Sat, Aug 21, 2021 at 03:55:32PM +0530, Srikar Dronamraju wrote:

quoted

Scheduler expects unique number of node distances to be available
at boot. It uses node distance to calculate this unique node
distances. On Power Servers, node distances for offline nodes is not
available. However, Power Servers already knows unique possible node
distances. Fake the offline node's distance_lookup_table entries so
that all possible node distances are updated.

For example distance info from numactl from a fully populated 8 node
system at boot may look like this.

node distances:
node   0   1   2   3   4   5   6   7
  0:  10  20  40  40  40  40  40  40
  1:  20  10  40  40  40  40  40  40
  2:  40  40  10  20  40  40  40  40
  3:  40  40  20  10  40  40  40  40
  4:  40  40  40  40  10  20  40  40
  5:  40  40  40  40  20  10  40  40
  6:  40  40  40  40  40  40  10  20
  7:  40  40  40  40  40  40  20  10

However the same system when only two nodes are online at boot, then
distance info from numactl will look like
node distances:
node   0   1
  0:  10  20
  1:  20  10

With the faked numa distance at boot, the node distance table will look
like
node   0   1   2
  0:  10  20  40
  1:  20  10  40
  2:  40  40  10

The actual distance will be populated once the nodes are onlined.

How did you want all this merged? I picked up Valentin's patch, do you
want me to pick up these PowerPC patches in the same tree, or do you
want to route them seperately?

While both (the patch you accepted and this series) together help solve the
problem, I think there is no hard dependency between the two. Hence I would
think it should be okay to go through the powerpc tree.

OK, works for me, thanks!