KVM: Note down when cpu relax intercepted or pause loop exited
Noting pause loop exited vcpu or cpu relax intercepted helps in
filtering right candidate to yield. Wrong selection of vcpu;
i.e., a vcpu that just did a pl-exit or cpu relax intercepted may
contribute to performance degradation.
Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com> # on s390x
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index db9aa917..361b36f 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -183,6 +183,18 @@
} async_pf;
#endif
+#ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
+ /*
+ * Cpu relax intercept or pause loop exit optimization
+ * in_spin_loop: set when a vcpu does a pause loop exit
+ * or cpu relax intercepted.
+ * dy_eligible: indicates whether vcpu is eligible for directed yield.
+ */
+ struct {
+ bool in_spin_loop;
+ bool dy_eligible;
+ } spin_loop;
+#endif
struct kvm_vcpu_arch arch;
};
@@ -898,5 +910,27 @@
}
}
+#ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
+
+static inline void kvm_vcpu_set_in_spin_loop(struct kvm_vcpu *vcpu, bool val)
+{
+ vcpu->spin_loop.in_spin_loop = val;
+}
+static inline void kvm_vcpu_set_dy_eligible(struct kvm_vcpu *vcpu, bool val)
+{
+ vcpu->spin_loop.dy_eligible = val;
+}
+
+#else /* !CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT */
+
+static inline void kvm_vcpu_set_in_spin_loop(struct kvm_vcpu *vcpu, bool val)
+{
+}
+
+static inline void kvm_vcpu_set_dy_eligible(struct kvm_vcpu *vcpu, bool val)
+{
+}
+
+#endif /* CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT */
#endif
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 68dda51..0892b75 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -239,6 +239,9 @@
}
vcpu->run = page_address(page);
+ kvm_vcpu_set_in_spin_loop(vcpu, false);
+ kvm_vcpu_set_dy_eligible(vcpu, false);
+
r = kvm_arch_vcpu_init(vcpu);
if (r < 0)
goto fail_free_run;
@@ -1585,6 +1588,7 @@
int pass;
int i;
+ kvm_vcpu_set_in_spin_loop(me, true);
/*
* We boost the priority of a VCPU that is runnable but not
* currently running, because it got preempted by something
@@ -1610,6 +1614,7 @@
}
}
}
+ kvm_vcpu_set_in_spin_loop(me, false);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_on_spin);