[v2,1/2] KVM: s390: count invalid yields
diff mbox series

Message ID 20191010110518.129256-2-borntraeger@de.ibm.com
State New
Headers show
Series
  • diag 9c improvements
Related show

Commit Message

Christian Borntraeger Oct. 10, 2019, 11:05 a.m. UTC
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@de.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
 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(-)

Comments

Cornelia Huck Oct. 10, 2019, 11:15 a.m. UTC | #1
On Thu, 10 Oct 2019 13:05:17 +0200
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> 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@de.ibm.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> ---
>  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(-)

Reviewed-by: Cornelia Huck <cohuck@redhat.com>

Patch
diff mbox series

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) },