On Oct 28, 2008, at 8:30 AM, Jerry Krinock wrote:
Although the documentation on message forwarding [1] explains that
alot of stuff needs to happen, it does not say "Warning: Don't do
this in performance-critical applications". So I made a test tool
which forwarded a simple message with one integer argument to a
class which would add it to its 'sum', an instance variable.
Sending this message 10,000 times and comparing the difference in
elapsed time with a similar task that sends a similar message
directly, I found that the average overhead for forwarding one
message on my Intel Core 2 Duo Mac Mini was about 20 microseconds.
That would be unacceptably slow for an iterated operation in a my
application, and I decided to not use message forwarding in this
particular case.
Has anyone ever seen better performance for message forwarding?
Jerry Krinock
Hi Jerry,
I take it you are using forwardInvocation:? NSInvocation is
heavyweight compared to a message send, as it needs to collect enough
state to be able to reproduce the message and its arguments at any
future date (and on any architecture, with DO).
If you don't want to store or pick apart the message, but only route
it immediately to another object, you should use the
forwardingTargetForSelector: method, which will be faster than
forwardInvocation:.
forwardingTargetForSelector: is new to Leopard and is mentioned in the
release notes at http://developer.apple.com/ReleaseNotes/Cocoa/Foundation.html
-Peter
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