DYLD_PRINT_STATISTICS output from device?

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Created Feb ’21

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Hi. We can see output from dyld, when adding the DYLD_PRINT_STATISTICS=1 env var, in the XCode console when running from simulator.

When running on device the statistics are not printed in either XCode console or Console.app.

Is there a way to get this info when running an app on device?

Answered by brianindeed in 662861022

Mea culpa. I prematurely optimized my scheme before running once and had turned off some of the standard checks in the Options and Diagnostics pane.

I performed some additional tests and isolated it down to the "Main Thread Checker". If you disable that, the dlyd statistics will not be printed.

This is using XCode 12.4 on MacOS 11.1

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Answer 1

DTS Engineer OP

Apple

Feb ’21

I was surprised that this failed so I tried it here in my office. I’m on macOS 11.1 running Xcode 12.4 to target iOS 14.4. A simple iOS app with DYLD_PRINT_STATISTICS set to 1 in the scheme prints these statistics:

Code Block  Total pre-main time:  95.07 milliseconds (100.0%)
         dylib loading time:  25.00 milliseconds (26.3%)
        rebase/binding time:  19.75 milliseconds (20.7%)
            ObjC setup time:   6.85 milliseconds (7.2%)
           initializer time:  43.45 milliseconds (45.7%)
           slowest intializers :
             libSystem.B.dylib :   8.43 milliseconds (8.8%)
   libBacktraceRecording.dylib :   9.00 milliseconds (9.4%)
    libMainThreadChecker.dylib :  22.05 milliseconds (23.1%)

How are you testing this?

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Answer 2

brianindeed OP

Feb ’21

Accepted Answer

Mea culpa. I prematurely optimized my scheme before running once and had turned off some of the standard checks in the Options and Diagnostics pane.

I performed some additional tests and isolated it down to the "Main Thread Checker". If you disable that, the dlyd statistics will not be printed.

This is using XCode 12.4 on MacOS 11.1

0