210920 2020-04-23 10:13:24 -0700 Improve API::SerializedScriptValue::deserialize to not allocate a new JSContext every second 2022-04-06 11:31:29 -0700 1 1 1 Unclassified WebKit WebKit API Safari 13 All All RESOLVED FIXED https://bugs.webkit.org/show_bug.cgi?id=146416 InRadar P2 Enhancement --- 1 simontaylor1 cdumez achristensen beidson cdumez darin ggaren guochongscut heycam mark.lam sam simontaylor1 webkit-bug-importer ysuzuki oldest_to_newest 1644823 0 simontaylor1 2020-04-23 10:13:24 -0700 In r186229 (related to bug 146416) a static API::SerializedScriptValue::deserialize() function was introduced. This function converts from a SerializedScriptValue to an Objective C object, and is currently used in the implementation of these APIs that return results from the content process: - evaluateJavaScript:completionHandler: for WKWebView, and - userContentController:didReceiveScriptMessage: for WKScriptMessageHandler SerializedScriptValue::deserialize uses a JSContext to do the conversion, with a SharedJSContext helper to cache this between calls so it does not need to create a completely fresh one each time (this was bug 146416). However the SharedJSContext clears the cached JSContext one second after its initial creation due to this line: https://trac.webkit.org/browser/webkit/trunk/Source/WebKit/UIProcess/API/Cocoa/APISerializedScriptValueCocoa.mm#L49 Any apps that make heavy use of passing data from the WKWebView to the native side therefore end up recreating the JSContext for the Objective C value conversion once per second. The most annoying implication of this is when debugging - this only-for-conversion JSContext shows up in Safari's Develop menu, and makes the options to automatically show inspector and pause JSContexts essentially useless. It was digging into what those were that led to this entire adventure :) There is also a small performance impact - from Instruments System Trace it looks like my iPod 7 spends around 1.5ms doing [[JSContext alloc] init]. It's only at most once per second, so not huge overall, but still would be nice to get rid of this cost. Here's my initial thoughts for improvements: - Reset the timeout to clear the shared JSContext in every ensureContext() call (so active use of evaluateJavascript will keep it around indefinitely) - Increment a ref count on the shared context for each WKScriptMessageHandler attached I don't know the memory cost of the shared JSContext, but attaching a WKScriptMessageHandler is a pretty clear signal the developer expects messages to be coming back from the WebView, so I'd argue keeping the shared context around in this case makes sense. 1852957 1 guochongscut 2022-03-19 03:16:18 -0700 Looks like a solution for this issue: WebKit::WebUserContentControllerProxy::didReceiveMessage spents long time on JSContext initailization. https://developer.apple.com/forums/thread/702626 1858824 2 456819 cdumez 2022-04-06 07:53:01 -0700 Created attachment 456819 Patch 1858901 3 456819 ggaren 2022-04-06 10:39:03 -0700 Comment on attachment 456819 Patch r=me 1858940 4 ews-feeder 2022-04-06 11:30:53 -0700 Committed r292483 (249334@main): <https://commits.webkit.org/249334@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 456819. 1858942 5 webkit-bug-importer 2022-04-06 11:31:29 -0700 <rdar://problem/91366573> 456819 2022-04-06 07:53:01 -0700 2022-04-06 11:30:55 -0700 Patch bug-210920-20220406075300.patch text/plain 3077 cdumez U3VidmVyc2lvbiBSZXZpc2lvbjogMjkyNDYzCmRpZmYgLS1naXQgYS9Tb3VyY2UvV2ViS2l0L0No YW5nZUxvZyBiL1NvdXJjZS9XZWJLaXQvQ2hhbmdlTG9nCmluZGV4IDdiN2Y1ZTBiMzEwNzIxYTIw NjZlNmRiMDg2OTQwYTg2NjM3ZTQ4YzkuLmI0YzYxNTBiODIwZjM0MzdkOWU4MGRhMzVmNjNkZDg0 MzBlNDliMGYgMTAwNjQ0Ci0tLSBhL1NvdXJjZS9XZWJLaXQvQ2hhbmdlTG9nCisrKyBiL1NvdXJj ZS9XZWJLaXQvQ2hhbmdlTG9nCkBAIC0xLDMgKzEsMTkgQEAKKzIwMjItMDQtMDYgIENocmlzIER1 bWV6ICA8Y2R1bWV6QGFwcGxlLmNvbT4KKworICAgICAgICBJbXByb3ZlIEFQSTo6U2VyaWFsaXpl ZFNjcmlwdFZhbHVlOjpkZXNlcmlhbGl6ZSB0byBub3QgYWxsb2NhdGUgYSBuZXcgSlNDb250ZXh0 IGV2ZXJ5IHNlY29uZAorICAgICAgICBodHRwczovL2J1Z3Mud2Via2l0Lm9yZy9zaG93X2J1Zy5j Z2k/aWQ9MjEwOTIwCisKKyAgICAgICAgUmV2aWV3ZWQgYnkgTk9CT0RZIChPT1BTISkuCisKKyAg ICAgICAgSW5zdGVhZCBvZiBmb3JjaW5nIHRoZSBsaWZldGltZSBvZiB0aGUgc2hhcmVkIEpTQ29u dGV4dCB0byAxIHNlY29uZCwgd2Ugbm93IHVzZSBhIGh5c3RlcmVzaXMKKyAgICAgICAgbG9naWMg c28gdGhhdCBpdCBjYW4gc3RheSBhbGl2ZSBhcyBsb25nIGFzIGl0IGlzIHVzZWQgYXQgbGVhc3Qg ZXZlcnkgMTAgc2Vjb25kcy4KKworICAgICAgICAqIFVJUHJvY2Vzcy9BUEkvQ29jb2EvQVBJU2Vy aWFsaXplZFNjcmlwdFZhbHVlQ29jb2EubW06CisgICAgICAgIChBUEk6OlNoYXJlZEpTQ29udGV4 dDo6U2hhcmVkSlNDb250ZXh0KToKKyAgICAgICAgKEFQSTo6U2hhcmVkSlNDb250ZXh0OjplbnN1 cmVDb250ZXh0KToKKyAgICAgICAgKEFQSTo6U2hhcmVkSlNDb250ZXh0OjpyZWxlYXNlQ29udGV4 dElmTmVjZXNzYXJ5KToKKyAgICAgICAgKEFQSTo6U2hhcmVkSlNDb250ZXh0OjpyZWxlYXNlQ29u dGV4dCk6IERlbGV0ZWQuCisKIDIwMjItMDQtMDYgIEtpbW1vIEtpbm51bmVuICA8a2tpbm51bmVu QGFwcGxlLmNvbT4KIAogICAgICAgICBNZWRpYSBhbmQgV2ViUlRDIGNvZGUgdXNlcyBUaHJlYWRN ZXNzYWdlUmVjZWl2ZXJSZWZDb3VudGVkIHdpdGggV29ya1F1ZXVlcwpkaWZmIC0tZ2l0IGEvU291 cmNlL1dlYktpdC9VSVByb2Nlc3MvQVBJL0NvY29hL0FQSVNlcmlhbGl6ZWRTY3JpcHRWYWx1ZUNv Y29hLm1tIGIvU291cmNlL1dlYktpdC9VSVByb2Nlc3MvQVBJL0NvY29hL0FQSVNlcmlhbGl6ZWRT Y3JpcHRWYWx1ZUNvY29hLm1tCmluZGV4IDg5NTUwNjExMzM0NDY1N2Q0NWViNTIyNzRjNDBhMjky ZjYxZjIzYzkuLjM4ZGMxNGIxODk3NzA0MWFhZDk5NmFjZDMzYWU2OGFjYjQ3YmMwNDQgMTAwNjQ0 Ci0tLSBhL1NvdXJjZS9XZWJLaXQvVUlQcm9jZXNzL0FQSS9Db2NvYS9BUElTZXJpYWxpemVkU2Ny aXB0VmFsdWVDb2NvYS5tbQorKysgYi9Tb3VyY2UvV2ViS2l0L1VJUHJvY2Vzcy9BUEkvQ29jb2Ev QVBJU2VyaWFsaXplZFNjcmlwdFZhbHVlQ29jb2EubW0KQEAgLTM2LDM0ICszNiw0NSBAQAogCiBu YW1lc3BhY2UgQVBJIHsKIAorc3RhdGljIGNvbnN0ZXhwciBhdXRvIHNoYXJlZEpTQ29udGV4dE1h eElkbGVUaW1lID0gMTBfczsKKwogY2xhc3MgU2hhcmVkSlNDb250ZXh0IHsKIHB1YmxpYzoKICAg ICBTaGFyZWRKU0NvbnRleHQoKQotICAgICAgICA6IG1fdGltZXIoUnVuTG9vcDo6bWFpbigpLCB0 aGlzLCAmU2hhcmVkSlNDb250ZXh0OjpyZWxlYXNlQ29udGV4dCkKKyAgICAgICAgOiBtX3RpbWVy KFJ1bkxvb3A6Om1haW4oKSwgdGhpcywgJlNoYXJlZEpTQ29udGV4dDo6cmVsZWFzZUNvbnRleHRJ Zk5lY2Vzc2FyeSkKICAgICB7CiAgICAgfQogCiAgICAgSlNDb250ZXh0KiBlbnN1cmVDb250ZXh0 KCkKICAgICB7CisgICAgICAgIG1fbGFzdFVzZVRpbWUgPSBNb25vdG9uaWNUaW1lOjpub3coKTsK ICAgICAgICAgaWYgKCFtX2NvbnRleHQpIHsKICAgICAgICAgICAgIGJvb2wgcHJldmlvdXMgPSBK U1JlbW90ZUluc3BlY3RvckdldEluc3BlY3Rpb25FbmFibGVkQnlEZWZhdWx0KCk7CiAgICAgICAg ICAgICBKU1JlbW90ZUluc3BlY3RvclNldEluc3BlY3Rpb25FbmFibGVkQnlEZWZhdWx0KGZhbHNl KTsKICAgICAgICAgICAgIG1fY29udGV4dCA9IGFkb3B0TlMoW1tKU0NvbnRleHQgYWxsb2NdIGlu aXRdKTsKICAgICAgICAgICAgIEpTUmVtb3RlSW5zcGVjdG9yU2V0SW5zcGVjdGlvbkVuYWJsZWRC eURlZmF1bHQocHJldmlvdXMpOwogCi0gICAgICAgICAgICBtX3RpbWVyLnN0YXJ0T25lU2hvdCgx X3MpOworICAgICAgICAgICAgbV90aW1lci5zdGFydE9uZVNob3Qoc2hhcmVkSlNDb250ZXh0TWF4 SWRsZVRpbWUpOwogICAgICAgICB9CiAgICAgICAgIHJldHVybiBtX2NvbnRleHQuZ2V0KCk7CiAg ICAgfQogCi0gICAgdm9pZCByZWxlYXNlQ29udGV4dCgpCisgICAgdm9pZCByZWxlYXNlQ29udGV4 dElmTmVjZXNzYXJ5KCkKICAgICB7CisgICAgICAgIGF1dG8gaWRsZVRpbWUgPSBNb25vdG9uaWNU aW1lOjpub3coKSAtIG1fbGFzdFVzZVRpbWU7CisgICAgICAgIGlmIChpZGxlVGltZSA8IHNoYXJl ZEpTQ29udGV4dE1heElkbGVUaW1lKSB7CisgICAgICAgICAgICAvLyBXZSBsYXppbHkgcmVzdGFy dCB0aGUgdGltZXIgaWYgbmVlZGVkIGV2ZXJ5IDEwIHNlY29uZHMgaW5zdGVhZCBvZiBkb2luZyBz byBldmVyeSB0aW1lIGVuc3VyZUNvbnRleHQoKQorICAgICAgICAgICAgLy8gaXMgY2FsbGVkLCBm b3IgcGVyZm9ybWFuY2UgcmVhc29ucy4KKyAgICAgICAgICAgIG1fdGltZXIuc3RhcnRPbmVTaG90 KHNoYXJlZEpTQ29udGV4dE1heElkbGVUaW1lIC0gaWRsZVRpbWUpOworICAgICAgICAgICAgcmV0 dXJuOworICAgICAgICB9CiAgICAgICAgIG1fY29udGV4dC5jbGVhcigpOwogICAgIH0KIAogcHJp dmF0ZToKICAgICBSZXRhaW5QdHI8SlNDb250ZXh0PiBtX2NvbnRleHQ7CiAgICAgUnVuTG9vcDo6 VGltZXI8U2hhcmVkSlNDb250ZXh0PiBtX3RpbWVyOworICAgIE1vbm90b25pY1RpbWUgbV9sYXN0 VXNlVGltZTsKIH07CiAKIHN0YXRpYyBTaGFyZWRKU0NvbnRleHQmIHNoYXJlZENvbnRleHQoKQo=