diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.cpp b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
index a8dcf98..6302053 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
@@ -524,6 +524,10 @@
             if (!err) {
                 int32_t& events(mDisplayData[disp].events);
                 events = (events & ~eventBit) | newValue;
+
+                char tag[16];
+                snprintf(tag, sizeof(tag), "HW_VSYNC_ON_%1u", disp);
+                ATRACE_INT(tag, enabled);
             }
         }
         // error here should not happen -- not sure what we should