Re: [v5] powerpc/topology: Get topology for shared processors at boot

Srikar Dronamraju [off-list ref] writes:

* Michael Ellerman [off-list ref] [2018-08-21 20:35=

:23]:

quoted

On Fri, 2018-08-17 at 14:54:39 UTC, Srikar Dronamraju wrote:

quoted

On a shared lpar, Phyp will not update the cpu associativity at boot
time. Just after the boot system does recognize itself as a shared lpa=

r and

quoted

quoted

trigger a request for correct cpu associativity. But by then the sched=

uler

quoted

quoted

would have already created/destroyed its sched domains.
=20
This causes
- Broken load balance across Nodes causing islands of cores.
- Performance degradation esp if the system is lightly loaded
- dmesg to wrongly report all cpus to be in Node 0.
- Messages in dmesg saying borken topology.
- With commit 051f3ca02e46 ("sched/topology: Introduce NUMA identity
  node sched domain"), can cause rcu stalls at boot up.
=20
=20
Previous attempt to solve this problem
https://patchwork.ozlabs.org/patch/530090/
=20
Reported-by: Manjunatha H R <redacted>
Signed-off-by: Srikar Dronamraju <redacted>

=20
Applied to powerpc next, thanks.
=20
https://git.kernel.org/powerpc/c/2ea62630681027c455117aa471ea3a
=20

Once it gets to Linus's tree, can we request this to be included in
stable trees?

You can yes.

I'd prefer if we wait a week or two so it can get some testing first.

cheers