Re: Cocoa application running very slow under 64 bit
Re: Cocoa application running very slow under 64 bit
- Subject: Re: Cocoa application running very slow under 64 bit
- From: Frank Illenberger <email@hidden>
- Date: Thu, 11 Sep 2008 13:01:05 +0200
Hi there,
I migrated an existing cocoa application to run under x86_64 with
Xcode 3.1 / Mac OS 10.5.4. The app still runs fine under 32 bit but
when started in x86_64 mode, it runs about 3-4 times slower.
A shark profile reveals the following hot traces:
8.9% libgcc_s.1.dylib _Unwind_GetIPInfo
7.6% libgcc_s.1.dylib _Unwind_GetIPInfo
7.6% libgcc_s.1.dylib _Unwind_Backtrace
7.6% libobjc.A.dylib objc_addExceptionHandler
7.5% Unknown Library _CFDoExceptionOperation
7.2% Unknown Library _NSAppKitLock
1.5% Unknown Library -[NSView nextKeyView]
1.2% Unknown Library -[NSView _primitiveSetNextKeyView:]
0.8% Unknown Library +[NSControl cellClass] [unknown]
0.7% Unknown Library -[NSCell setMnemonicLocation:]
0.6% Unknown Library SetPlaceholderString
0.5% Unknown Library -[NSView previousKeyView]
0.2% Unknown Library -[NSControl
_setControlTextDelegateFromOld:toNew:]
These hot traces do not show up when I profile the app running
under 32 bit.
Does anybody know why a 64 bit app could be spending so much time
in these methods?
Is your program throwing a lots of exceptions ? The exception
handling mechanism is not the same between 32 bits and 64 bits
runtime. IIRC throwing an exception on the 64 bits runtime os a lot
more than on the 32 bits one.
With the 64bits runtime, it will properly unwind the stack and call C
++ dtor when needed (even if a pure objc program does not require
it), but with the 32bits runtime, it's just a longjmp call.
I am not throwing any exceptions in my code. If there are any, they
must get thrown from within the Cocoa frameworks. Is there a way to
track this? I added breakpoints at
objc_exception_throw
and
-[NSException initWithName:reason:userInfo:]
but they were not hit.
Cheers
Frank
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