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

[Peter Zijlstra]

On Mon, Aug 23, 2021 at 03:04:37PM +0530, Srikar Dronamraju wrote:
> * Peter Zijlstra <peterz at infradead.org> [2021-08-23 10:33:30]:
> 
> > On Sat, Aug 21, 2021 at 03:55:32PM +0530, Srikar Dronamraju wrote:
> > > 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!