[webkit-dev] JavaScriptCore performance is very slow on Windows

Filip Pizlo fpizlo at apple.com
Mon Jun 29 10:01:52 PDT 2015

WebKit-dev is really not the place where you should be posting performance problems. Please create a bug on bugs.webkit.org. 

In this case please CC people working on the Windows port. 


> On Jun 29, 2015, at 9:51 AM, Eric Wing <ewmailing at gmail.com> wrote:
> Hi,
> I’ve been trying to use JavaScriptCore as an embedded scripting
> language for a video game engine. (Note: I am just using JSCore, not
> WebKit.) I’ve been using it on multiple platforms. During my testing,
> I’ve discovered that the JavaScriptCore Windows performance is very
> slow. I wanted to alert you in hopes there is something that can be
> done to fix it.
> I’ve been getting help on building JavaScriptCore for Windows from a
> few people in the community. My current build is as of a couple of
> weeks ago. However, I’ve been seeing the same performance
> characteristics from a build from a little over a year ago.
> To prove to you that this is a problem to just JavaScriptCore on
> Windows, and not a general Windows problem, nor a problem with my
> code, I have done the following:
> - I ran the program on Windows, OS X, Linux, iOS, Android, and
> Raspberry Pi (Linux).
> - I wrote comparable programs in C and Lua and also ran these on all platforms.
> - Additionally, I was able to run on the same hardware (dual boot) for
> Windows/Linux.
> So here is the quick summary:
>                   Ubuntu 12.04 LTS (64-bit)
> Windows 8.1 (64-bit)
> ===========================================================
> C                     5600 sprites
>         27000 sprites
> Lua                  3100 sprites
>       12000 sprites
> JSCore            2400 sprites
>     120 sprites
> This was on an Intel Core i5-3570K @ 3.40 GHz with Intel 4000 HD
> graphics. The reason for the big jump in Windows performance is mostly
> due to the Intel graphics drivers being poor on Linux. However, that
> 120 sprites is not a typo. Whereas everything else was faster on
> Windows, JSCore is magnitudes slower.
> My numbers for the other operating systems tend to follow sensible
> trends. Windows/JSCore is an outlier. And other programs I’ve run also
> show JavaScriptCore on Windows has performance problems.
> You can see this summary with the programs running in a short video I
> put together and uploaded to YouTube:
> https://youtu.be/UDyI1cckDJI
> I have uploaded pre-built binaries of my test program. JavaScriptCore
> is dynamically linked in all cases, so it is easy to swap in another
> build of JSCore if you want to try things. There is a file called
> config.txt in each bundle that lets you change the number of sprites.
> (I did not sign the OS X binaries with my Developer ID because I
> figured you might want to change the config.txt.) Also, the Lua and
> JavaScript scripts are in plain text and can be easily modified.
> And for clarity: All my test programs here are 64-bit versions. I have
> not actually benchmarked 32-bit except on ARM devices.
> Windows 7 and up (x64)
> Zip:
> http://playcontrol.net/tempdownload/WebKit/MinimalSDLSpriteBenchmarkC.zip
> http://playcontrol.net/tempdownload/WebKit/MinimalSDLSpriteBenchmarkLua.zip
> http://playcontrol.net/tempdownload/WebKit/MinimalSDLSpriteBenchmarkJavaScript.zip
> Installer:
> http://playcontrol.net/tempdownload/WebKit/MinimalSDLSpriteBenchmarkC-1.0.0-win64.exe
> http://playcontrol.net/tempdownload/WebKit/MinimalSDLSpriteBenchmarkLua-1.0.0-win64.exe
> http://playcontrol.net/tempdownload/WebKit/MinimalSDLSpriteBenchmarkJavaScript-1.0.0-win64.exe
> OS X 10.9 and up
> http://playcontrol.net/tempdownload/WebKit/MinimalSDLSpriteBenchmarkC.app.zip
> http://playcontrol.net/tempdownload/WebKit/MinimalSDLSpriteBenchmarkLua.app.zip
> http://playcontrol.net/tempdownload/WebKit/MinimalSDLSpriteBenchmarkJavaScript.app.zip
> Linux (x64 Ubuntu 12.04 LTS a.k.a Steam Runtime)
> http://playcontrol.net/tempdownload/WebKit/MinimalSDLSpriteBenchmarkC-0.1.1-Linux.tar.gz
> http://playcontrol.net/tempdownload/WebKit/MinimalSDLSpriteBenchmarkLua-0.1.1-Linux.tar.gz
> http://playcontrol.net/tempdownload/WebKit/MinimalSDLSpriteBenchmarkJavaScript-0.1.1-Linux.tar.gz
> I also made the repos to my programs available:
> https://bitbucket.org/blurrr/minimalspritebenchmarkc
> https://bitbucket.org/blurrr/minimalspritebenchmarklua
> https://bitbucket.org/blurrr/minimalspritebenchmarkjavascript
> However, it probably won’t be of much use without my SDK because
> without it, you’ll need to compile all the dependencies yourself and
> figure out the build system. If you need a copy of my SDK, let me
> know.
> Thanks,
> Eric
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