[PATCH 3/3] KVM: X86: Tune PLE Window tracepoint

[Peter Xu <zhexu@redhat.com>]

The PLE window tracepoint triggers easily and it can be a bit
confusing too.  One example line:

  kvm_ple_window: vcpu 0: ple_window 4096 (shrink 4096)

It easily let people think of "the window now is 4096 which is
shrinked", but the truth is the value actually didn't change (4096).

Let's only dump this message if the value really changed, and we make
the message even simpler like:

  kvm_ple_window: vcpu 4 (4096 -> 8192)

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 arch/x86/kvm/svm.c     |  8 ++++----
 arch/x86/kvm/trace.h   | 22 +++++++++-------------
 arch/x86/kvm/vmx/vmx.c |  4 ++--
 3 files changed, 15 insertions(+), 19 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 48c865a4e5dd..0d365b621b5a 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1268,8 +1268,8 @@ static void grow_ple_window(struct kvm_vcpu *vcpu)
 	if (control->pause_filter_count != old)
 		mark_dirty(svm->vmcb, VMCB_INTERCEPTS);
 
-	trace_kvm_ple_window_grow(vcpu->vcpu_id,
-				  control->pause_filter_count, old);
+	trace_kvm_ple_window_changed(vcpu->vcpu_id,
+				     control->pause_filter_count, old);
 }
 
 static void shrink_ple_window(struct kvm_vcpu *vcpu)
@@ -1286,8 +1286,8 @@ static void shrink_ple_window(struct kvm_vcpu *vcpu)
 	if (control->pause_filter_count != old)
 		mark_dirty(svm->vmcb, VMCB_INTERCEPTS);
 
-	trace_kvm_ple_window_shrink(vcpu->vcpu_id,
-				    control->pause_filter_count, old);
+	trace_kvm_ple_window_changed(vcpu->vcpu_id,
+				     control->pause_filter_count, old);
 }
 
 static __init int svm_hardware_setup(void)
diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index 76a39bc25b95..91c91f358b23 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -891,34 +891,30 @@ TRACE_EVENT(kvm_pml_full,
 );
 
 TRACE_EVENT(kvm_ple_window,
-	TP_PROTO(bool grow, unsigned int vcpu_id, int new, int old),
-	TP_ARGS(grow, vcpu_id, new, old),
+	TP_PROTO(unsigned int vcpu_id, int new, int old),
+	TP_ARGS(vcpu_id, new, old),
 
 	TP_STRUCT__entry(
-		__field(                bool,      grow         )
 		__field(        unsigned int,   vcpu_id         )
 		__field(                 int,       new         )
 		__field(                 int,       old         )
 	),
 
 	TP_fast_assign(
-		__entry->grow           = grow;
 		__entry->vcpu_id        = vcpu_id;
 		__entry->new            = new;
 		__entry->old            = old;
 	),
 
-	TP_printk("vcpu %u: ple_window %d (%s %d)",
-	          __entry->vcpu_id,
-	          __entry->new,
-	          __entry->grow ? "grow" : "shrink",
-	          __entry->old)
+	TP_printk("vcpu %u (%d -> %d)",
+	          __entry->vcpu_id, __entry->old, __entry->new)
 );
 
-#define trace_kvm_ple_window_grow(vcpu_id, new, old) \
-	trace_kvm_ple_window(true, vcpu_id, new, old)
-#define trace_kvm_ple_window_shrink(vcpu_id, new, old) \
-	trace_kvm_ple_window(false, vcpu_id, new, old)
+#define trace_kvm_ple_window_changed(vcpu, new, old)		\
+	do {							\
+		if (old != new)					\
+			trace_kvm_ple_window(vcpu, new, old);	\
+	} while (0)
 
 TRACE_EVENT(kvm_pvclock_update,
 	TP_PROTO(unsigned int vcpu_id, struct pvclock_vcpu_time_info *pvclock),
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d98eac371c0a..cc1f98130e6a 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5214,7 +5214,7 @@ static void grow_ple_window(struct kvm_vcpu *vcpu)
 	if (vmx->ple_window != old)
 		vmx->ple_window_dirty = true;
 
-	trace_kvm_ple_window_grow(vcpu->vcpu_id, vmx->ple_window, old);
+	trace_kvm_ple_window_changed(vcpu->vcpu_id, vmx->ple_window, old);
 }
 
 static void shrink_ple_window(struct kvm_vcpu *vcpu)
@@ -5229,7 +5229,7 @@ static void shrink_ple_window(struct kvm_vcpu *vcpu)
 	if (vmx->ple_window != old)
 		vmx->ple_window_dirty = true;
 
-	trace_kvm_ple_window_shrink(vcpu->vcpu_id, vmx->ple_window, old);
+	trace_kvm_ple_window_changed(vcpu->vcpu_id, vmx->ple_window, old);
 }
 
 /*
-- 
2.21.0