On 8/3/21 10:57 AM, Pierre Morel wrote:
On 8/3/21 10:42 AM, Heiko Carstens wrote:
On Tue, Aug 03, 2021 at 10:26:46AM +0200, Pierre Morel wrote:
Now that the PTF instruction is interpreted by the SIE we can optimize
the arch_update_cpu_topology callback to check if there is a real need
to update the topology by using the PTF instruction.
Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
arch/s390/kernel/topology.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/s390/kernel/topology.c b/arch/s390/kernel/topology.c
index 26aa2614ee35..741cb447e78e 100644
--- a/arch/s390/kernel/topology.c
+++ b/arch/s390/kernel/topology.c
@@ -322,6 +322,9 @@ int arch_update_cpu_topology(void)
struct device *dev;
int cpu, rc;
+ if (!ptf(PTF_CHECK))
+ return 0;
+
We have a timer which checks if topology changed and then triggers a
call to arch_update_cpu_topology() via rebuild_sched_domains().
With this change topology changes would get lost.
For my understanding, if PTF check return 0 it means that there are no
topology changes.
So they could not get lost.
What did I miss?
I missed that PTF clears the MCTR... and only one of the two calls will
return 1 while we need both to return 1...
--
Pierre Morel
IBM Lab Boeblingen
