KVM: X86: Tune PLE Window tracepoint

The PLE window tracepoint triggers even if the window is not changed,
and the wording 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 old 4096 new 8192 (growed)
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm.c

@@ -1266,11 +1266,11 @@ static void grow_ple_window(struct kvm_vcpu *vcpu)
 							pause_filter_count_grow,
 							pause_filter_count_max);
 
-	if (control->pause_filter_count != old)
+	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_update(vcpu->vcpu_id,
+					    control->pause_filter_count, old);
+	}
 }
 
 static void shrink_ple_window(struct kvm_vcpu *vcpu)
@@ -1284,11 +1284,11 @@ static void shrink_ple_window(struct kvm_vcpu *vcpu)
 						    pause_filter_count,
 						    pause_filter_count_shrink,
 						    pause_filter_count);
-	if (control->pause_filter_count != old)
+	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_update(vcpu->vcpu_id,
+					    control->pause_filter_count, old);
+	}
 }
 
 static __init int svm_hardware_setup(void)

arch/x86/kvm/trace.h

@@ -890,37 +890,27 @@ TRACE_EVENT(kvm_pml_full,
 	TP_printk("vcpu %d: PML full", __entry->vcpu_id)
 );
 
-TRACE_EVENT(kvm_ple_window,
-	TP_PROTO(bool grow, unsigned int vcpu_id, unsigned int new,
-		 unsigned int old),
-	TP_ARGS(grow, vcpu_id, new, old),
+TRACE_EVENT(kvm_ple_window_update,
+	TP_PROTO(unsigned int vcpu_id, unsigned int new, unsigned int old),
+	TP_ARGS(vcpu_id, new, old),
 
 	TP_STRUCT__entry(
-		__field(                bool,      grow         )
 		__field(        unsigned int,   vcpu_id         )
 		__field(        unsigned int,       new         )
 		__field(        unsigned 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 %u (%s %u)",
-	          __entry->vcpu_id,
-	          __entry->new,
-	          __entry->grow ? "grow" : "shrink",
-	          __entry->old)
+	TP_printk("vcpu %u old %u new %u (%s)",
+	          __entry->vcpu_id, __entry->old, __entry->new,
+		  __entry->old < __entry->new ? "growed" : "shrinked")
 );
 
-#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)
-
 TRACE_EVENT(kvm_pvclock_update,
 	TP_PROTO(unsigned int vcpu_id, struct pvclock_vcpu_time_info *pvclock),
 	TP_ARGS(vcpu_id, pvclock),

arch/x86/kvm/vmx/vmx.c

@@ -5243,10 +5243,11 @@ static void grow_ple_window(struct kvm_vcpu *vcpu)
 					    ple_window_grow,
 					    ple_window_max);
 
-	if (vmx->ple_window != old)
+	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_update(vcpu->vcpu_id,
+					    vmx->ple_window, old);
+	}
 }
 
 static void shrink_ple_window(struct kvm_vcpu *vcpu)
@@ -5258,10 +5259,11 @@ static void shrink_ple_window(struct kvm_vcpu *vcpu)
 					      ple_window_shrink,
 					      ple_window);
 
-	if (vmx->ple_window != old)
+	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_update(vcpu->vcpu_id,
+					    vmx->ple_window, old);
+	}
 }
 
 /*

arch/x86/kvm/x86.c

@@ -10098,7 +10098,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_invlpga);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_skinit);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_nested_intercepts);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_write_tsc_offset);
-EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_ple_window);
+EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_ple_window_update);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_pml_full);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_pi_irte_update);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_avic_unaccelerated_access);