To analyze some performance issues with lock contention and scheduling
it is nice to know when diag9c did not result in any action or when
no action was tried.
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
---
arch/s390/include/asm/kvm_host.h | 1 +
arch/s390/kvm/diag.c | 18 ++++++++++++++----
arch/s390/kvm/kvm-s390.c | 1 +
3 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index abe60268335d..02f4c21c57f6 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -392,6 +392,7 @@ struct kvm_vcpu_stat {
u64 diagnose_10;
u64 diagnose_44;
u64 diagnose_9c;
+ u64 diagnose_9c_ignored;
u64 diagnose_258;
u64 diagnose_308;
u64 diagnose_500;
diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
index 45634b3d2e0a..609c55df3ce8 100644
--- a/arch/s390/kvm/diag.c
+++ b/arch/s390/kvm/diag.c
@@ -158,14 +158,24 @@ static int __diag_time_slice_end_directed(struct kvm_vcpu *vcpu)
tid = vcpu->run->s.regs.gprs[(vcpu->arch.sie_block->ipa & 0xf0) >> 4];
vcpu->stat.diagnose_9c++;
- VCPU_EVENT(vcpu, 5, "diag time slice end directed to %d", tid);
+ /* yield to self */
if (tid == vcpu->vcpu_id)
- return 0;
+ goto no_yield;
+ /* yield to invalid */
tcpu = kvm_get_vcpu_by_id(vcpu->kvm, tid);
- if (tcpu)
- kvm_vcpu_yield_to(tcpu);
+ if (!tcpu)
+ goto no_yield;
+
+ if (kvm_vcpu_yield_to(tcpu) <= 0)
+ goto no_yield;
+
+ VCPU_EVENT(vcpu, 5, "diag time slice end directed to %d: done", tid);
+ return 0;
+no_yield:
+ VCPU_EVENT(vcpu, 5, "diag time slice end directed to %d: ignored", tid);
+ vcpu->stat.diagnose_9c_ignored++;
return 0;
}
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 4a3bc40ca1a4..d9e6bf3d54f0 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -155,6 +155,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
{ "instruction_diag_10", VCPU_STAT(diagnose_10) },
{ "instruction_diag_44", VCPU_STAT(diagnose_44) },
{ "instruction_diag_9c", VCPU_STAT(diagnose_9c) },
+ { "diag_9c_ignored", VCPU_STAT(diagnose_9c_ignored) },
{ "instruction_diag_258", VCPU_STAT(diagnose_258) },
{ "instruction_diag_308", VCPU_STAT(diagnose_308) },
{ "instruction_diag_500", VCPU_STAT(diagnose_500) },
--
2.21.0
