Merge pull request #3508 from lightpanda-io/improve-js-memory-metric

ops: improve v8 memory metric reporting

src/browser/Browser.zig

@@ -55,6 +55,7 @@ arena_account: lp.Arena.Account = .{},
 
 // Our isolate's heap size as of the last reportJsHeap().
 last_reported_js_bytes: usize = 0,
+last_js_heap_sample_ms: u64 = 0,
 
 // Permission state set via CDP Browser.grantPermissions / setPermission /
 // resetPermissions, keyed by permission name (e.g. "geolocation"). Read back
@@ -236,6 +237,18 @@ pub fn reportJsHeap(self: *Browser) void {
     self.last_reported_js_bytes = bytes;
 }
 
+// Called every Runner tick
+pub fn sampleJsHeap(self: *Browser) void {
+    const now = lp.datetime.milliTimestamp(.boot);
+    if (now - self.last_js_heap_sample_ms < 1000) {
+        // a busy page ticks often, we don't need to track this more than once
+        // per second
+        return;
+    }
+    self.last_js_heap_sample_ms = now;
+    self.reportJsHeap();
+}
+
 pub fn runMicrotasks(self: *Browser) void {
     self.env.runMicrotasks();
 }

src/browser/Frame.zig

@@ -498,11 +498,6 @@ pub fn init(self: *Frame, frame_id: u32, page: *Page, opts: InitOpts) !void {
             }.runIdleTasks, 200, .{ .name = "frame.runIdleTasks", .blocks_done = false });
         }
     }
-
-    if (parent == null) {
-        // no point reporting this for each child page
-        session.browser.reportJsHeap();
-    }
 }
 
 pub fn deinit(self: *Frame) void {
@@ -576,9 +571,6 @@ pub fn deinit(self: *Frame) void {
     const browser = page.session.browser;
 
     browser.http_client.abortOwner(&self._http_owner);
-    if (self.parent == null) {
-        browser.reportJsHeap();
-    }
 
     // fired the last moment the js context is still alive
     page.session.notification.dispatch(.frame_destroyed, self);
@@ -1313,10 +1305,6 @@ pub fn documentIsComplete(self: *Frame) void {
         self._maybe_meta_refresh = false;
         self.metaRefreshOnLoad();
     }
-
-    if (self.parent == null) {
-        self._session.browser.reportJsHeap();
-    }
 }
 
 fn _documentIsComplete(self: *Frame) !void {

src/browser/Runner.zig

@@ -204,7 +204,10 @@ fn _tick(self: *Runner, comptime is_cdp: bool, timeout_ms: u32, conditions: []Wa
     const session = self.session;
     const browser = self.browser;
     const http_client = self.http_client;
-    defer browser.flushArenaMemory();
+    defer {
+        browser.flushArenaMemory();
+        browser.sampleJsHeap();
+    }
 
     // Arms the watchdog (and proves liveness): a stall anywhere in this tick
     // ages this stamp until the watchdog fires.