Why libglInterpose.dylib loaded so slowly?

App & System Services Core OS
cleexiang
cleexiang OP
Created Jul ’16
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Total pre-main time: 980.70 milliseconds (100.0%)
         dylib loading time:  23.06 milliseconds (2.3%)
        rebase/binding time: 121.75 milliseconds (12.4%)
            ObjC setup time:  76.00 milliseconds (7.7%)
           initializer time: 759.73 milliseconds (77.4%)
           slowest intializers :
             libSystem.B.dylib :  16.47 milliseconds (1.6%)
   libBacktraceRecording.dylib :  26.70 milliseconds (2.7%)
          libglInterpose.dylib : 570.64 milliseconds (58.1%)
                     Camera360 : 208.81 milliseconds (21.2%)


When I use DYLD_PRINT_STATISTICS to measure startup time, The console show libglInterpose.dylib costs 570ms, Why?


Answered by DTS Engineer in 158373022

Interposing is a debugging technology and thus the cost to load interposing libraries is generally not considered relevant. I recommend you separate your graphics profiling work from your app launch time profiling work.

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Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware 

let myEmail = "eskimo" + "1" + "@apple.com"
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Apple Staff, DTS Engineer
DTS Engineer OP
Apple
Jul ’16
Accepted Answer

Interposing is a debugging technology and thus the cost to load interposing libraries is generally not considered relevant. I recommend you separate your graphics profiling work from your app launch time profiling work.

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware 

let myEmail = "eskimo" + "1" + "@apple.com"
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cleexiang
cleexiang OP
Jul ’16

Do you means it's only happens for Debug model?

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Apple Staff, DTS Engineer
DTS Engineer OP
Apple
Aug ’16

Do you means it's only happens for Debug model?

I’m not sure what you mean by “Debug model” but I will say that this library is part of Xcode’s debugging infrastructure. I’m not entirely sure what it does (I think it’s part of the OpenGL debugger, but OpenGL isn’t really my thing so I don’t know for sure) but it’s definitely part of Xcode:

$ find /Applications/Xcode.app -name libglInterpose.dylib

/Applications/Xcode.app/Contents/SharedFrameworks/GPUTools.framework/Versions/A/Resources/libglInterpose.dylib

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware 

let myEmail = "eskimo" + "1" + "@apple.com"
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Why libglInterpose.dylib loaded so slowly?
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