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: Bill Bumgarner <email@hidden>
- Date: Thu, 11 Sep 2008 09:15:49 -0700
On Sep 11, 2008, at 8:47 AM, Frank Illenberger wrote:
As I understand it, try/catch blocks should be very fast (zero cost)
in the 64 bit evironment. As I can't observe the generation of any
exceptions, there has to be some other reason for the slow
performance. I can't find any documentation about
objc_addExceptionHandler, so I don't know if it is only called when
there are exceptions. Telling from the Shark trace, I guess the time
is spent generating backtraces. But for what purpose?
A little more information.
C++ exceptions and, under the modern ABI, Objective-C exceptions are
extremely cheap to set up (@try), but expensive to @throw and @catch.
When the @throw happens, there is a heavy cost to generating the bits
necessary to properly unwind the stack.
Unfortunately, the AppKit has an issue where it causes the unwind info
to be generated as a normal part of its operation (without throwing an
exception).
Thus, certain AppKit operations in 64 bit can be quite slow at this
time.
b.bum
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