Got it. Good to know this. Thanks a lot. 在2022年10月18日星期二 UTC+8 18:02:52<ma...@chromium.org> 写道：
> I'd say at that point we're at the expected range of slowdown, given less > optimization opportunities and no ICs when you go through the API. > > > On Tue, Oct 18, 2022 at 11:04 AM James Chen <dumg...@gmail.com> wrote: > >> @Marja , According to your suggestion, I updated the test case with more >> random string access instead of const string. The new result is that CPP >> test case performs 2~3 times slower than JS test case now. >> >> I posted more detail information at the end of >> https://github.com/cocos/cocos-engine/issues/12878 here . >> >> 2~3 times slower is still not good enough for us to switch >> deserialization logic from JS to CPP. >> So, is 2~3 times slower expected ？ Or are there more things I could do? >> >> > In addition to what Marja said, I assume that a significant difference >> (even without JIT) is that JavaScript can use Inline Caches, whereas the >> API cannot. >> >> @Jakob, Thank you for pointing me out that inline caches also make some >> optimizations. >> >> >> 在2022年10月17日星期一 UTC+8 17:54:34<Jakob Kummerow> 写道： >> >>> In addition to what Marja said, I assume that a significant difference >>> (even without JIT) is that JavaScript can use Inline Caches, whereas the >>> API cannot. >>> >>> >>> On Mon, Oct 17, 2022 at 10:34 AM James Chen <dumg...@gmail.com> wrote: >>> >>>> Got it. I would modify my test code to see whether the result could >>>> get better. >>>> >>>> Thanks for your reply. :) >>>> >>>> 在2022年10月17日星期一 UTC+8 13:59:35<ma...@chromium.org> 写道： >>>> >>>>> Hi, >>>>> >>>>> I didn't have a deep look, but your benchmarking might not be >>>>> representative. >>>>> >>>>> 1) V8 probably optimizes such a tight loop a lot (in the JIT mode). >>>>> You're using string constants as property names, and V8 sees the whole >>>>> object creation code at once, and can generate better optimized code. >>>>> When >>>>> we only need to do one v8::Object::Set, we can't do the same >>>>> optimizations. >>>>> (Very hand-wavy explanation; I didn't look at the actual generated code >>>>> in >>>>> this case.) If you make the object shape and property names + values more >>>>> unpredictable (also if you make the benchmark closer to what your actual >>>>> deserializer does), you might see a smaller difference. You'll also need >>>>> to >>>>> take into account the time needed for V8 to parse + compile the code, not >>>>> only the JS execution time. >>>>> >>>>> 2) The string creation (for the property names) is done when we parse >>>>> the JS code, so it's outside your benchmark timer. In your C++ version, I >>>>> assume it's inside your benchmark timer. >>>>> >>>>> The "16 times faster in the non-JIT mode" is a bit high though, I >>>>> would've guessed the difference would be smaller. >>>>> >>>>> Cheers, >>>>> >>>>> On Mon, Oct 17, 2022 at 4:12 AM James Chen <dumg...@gmail.com> wrote: >>>>> >>>>>> Hello V8 team, thanks for making V8 engine which could run JavaScript >>>>>> super fast. >>>>>> >>>>>> Recently, I want to improve the performance of deserialization for >>>>>> Cocos Creator game engine. >>>>>> >>>>>> Cocos Creator uses V8 for its default JavaScript engine and benefited >>>>>> from V8's high performance. There're many classes implemented in JS and >>>>>> some implemented in C++. And there will be more and more JS code moved >>>>>> to >>>>>> C++ side. >>>>>> >>>>>> I thought about deserializing game assets directly in C++ rather than >>>>>> in JS to get better performance since I think C++ code should be faster. >>>>>> >>>>>> Therefore, I wrote a testcase to test whether we could get benefited >>>>>> from C++ code. But unfortunately, I got a really bad result saying that >>>>>> create JS object and setting properties in C++ by V8 API is really >>>>>> slower >>>>>> than doing that in JS. It's about 50 times slower, in another word, JS >>>>>> execution is really fast. >>>>>> >>>>>> I debugged a little bit and found that the most heavy cost is in >>>>>> v8::Object::Set and v8::String::NewFromUtf8. >>>>>> >>>>>> Part of JS test code: >>>>>> const testArr = new Array<MySerializationTestClass>(this.loopCount); >>>>>> const start = performance.now(); >>>>>> >>>>>> for (let i = 0; i < this.loopCount; ++i) { >>>>>> const test = new MySerializationTestClass(); >>>>>> testArr[i] = test; >>>>>> >>>>>> test['booleanValue'] = false; >>>>>> test['nullValue'] = null; >>>>>> test['undefinedValue'] = undefined; >>>>>> test['numberValue0'] = 100.123; >>>>>> test['numberValue1'] = 230.2345; >>>>>> test['numberValue2'] = 330.2345; >>>>>> test['numberValue3'] = 430.2345; >>>>>> test['numberValue4'] = 530.2345; >>>>>> >>>>>> test['stringValue0'] = 'hello 0'; >>>>>> >>>>>> test['stringValue1'] = 'hello 1'; >>>>>> >>>>>> The logic of CPP test code is the same as which in the above JS test >>>>>> code. The difference is that we use v8::Object::Set API. >>>>>> >>>>>> ### JIT Enabled >>>>>> >>>>>> Cpp code is 55 times slower than JS code. >>>>>> >>>>>> ### JIT Disabled >>>>>> >>>>>> Cpp code is 16 times slower than JS code. >>>>>> >>>>>> >>>>>> ### Xcode Profile >>>>>> >>>>>> >>>>>> `v8::Maybe<bool> ret = >>>>>> _obj.handle(__isolate)->Set(__isolate->GetCurrentContext(), >>>>>> nameValue.ToLocalChecked(), value);` and `v8::String::NewFromUtf8` are >>>>>> the >>>>>> main hotspots. >>>>>> >>>>>> ### What I guess >>>>>> >>>>>> I guess running JS code directly could make use of the optimization >>>>>> by V8 Bytecode and JIT by TurboFan. But invoking V8 C++ API will not get >>>>>> the optimization. >>>>>> >>>>>> >>>>>> Could you point me out that whether my guess is correct or not? Also, >>>>>> is there a better V8 API for setting property? 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