406671 - nsWindowSH::GetProperty() is slow.

Status: RESOLVED FIXED

(Core :: DOM: Core & HTML, defect)

Description

[Johnny Stenback (:jst)]

Attachment: Don't call GetWrappedNativeOfJSObject unless we're likely to find what we need.

nsWindowSH::GetProperty() is showing up pretty high in profiles, and can be made faster. The biggest offender is the call to XPConnect's GetWrappedNativeOfJSObject(), which we call to check if the cached property value is a window object, and we do that so that the wrappers (XPCSafeJSObjectWrapper and XPCCrossOriginWrapper) can do the proper wrapping of the values. We can trivially avoid most of the calls into GetWrappedNativeOfJSObject() by checking if the JSClass name is such that the value is likely to be a window, and only then do the expensive call. This shaves off about 9% of the XPConnect overhead as seen in bug 375225.

Patch coming up.

Comment 1

[Peter Van der Beken [:peterv]]

Comment on attachment 291329 [details] [diff] [review]
Don't call GetWrappedNativeOfJSObject unless we're likely to find what we need.

>diff --git a/dom/src/base/nsDOMClassInfo.cpp b/dom/src/base/nsDOMClassInfo.cpp

>+    if ((*name == 'W' && strcmp(name, "Window") == 0) ||
>+        (*name == 'C' && strcmp(name, "ChromeWindow") == 0)) {

This needs to handle ModalContentWindow too. Maybe add a comment to make it clear that it is vital to keep this list up-to-date.

Comment 2

[Johnny Stenback (:jst)]

Fix checked in.