KVM: s390: count invalid yields

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

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index abe60268335d2027df8a36b0517755d25e1789fa..02f4c21c57f6ab0e5ea277196e9eae0604ecad0f 100644 (file)
--- 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 45634b3d2e0aedf90ece3f2c715e6ab9e53d9f00..609c55df3ce862be7a3884a90a27446a5e61d3f2 100644 (file)
--- 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 40af442b2e150aafc65b15e99509b01c2fc36f17..3b5ebf48f8028a9541ad6bcda203cbaaa04c4404 100644 (file)
--- 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) },