On Fri, Mar 12, 2010 at 5:41 PM, Gwynne Raskind <gwy...@darkrainfall.org> wrote:
> On Mar 12, 2010, at 4:52 PM, Peter Ammon wrote:
>>> While profiling a project I'm working on, I found that while most of my
>>> time was being spent in glFlush() (which is completely expected for an
>>> OpenGL-based game), a non-trivial amount of time is being spent in dozens
>>> of KVO internal methods and functions. Most especially, I noticed that KVO
>>> (or possibly the KVC beneath it) makes heavy use of NSInvocation-based
>>> forwarding, which is known to be the slowest possible code path for message
>>> dispatch.
>> I think KVO only uses NSInvocation when setting or getting non-standard
>> aggregate types. So if your property is any primitive C type, any ObjC
>> object, or an NSPoint, NSRect, NSRange, or NSSize, then it will not use
>> NSInvocation. If it's a custom struct it will. Does that seem plausible
>> based on what your property types are?
>>
>> If not, it would be helpful to post a backtrace for the call to
>> +[NSInvocation invocationWithMethodSignature:], so we can figure out what's
>> happening.
>
>
> You're right; the specific call that's causing the worst speed issues is
> returning a property typed with this structure:
>
> typedef struct { int32_t x, y; } IntegerPoint;
>
> It's not necessarily feasible to switch this to an NSPoint; it means digging
> up every point in the code that relies on signed 32-bit integer math and
> doing manual typecasting (or calling lround()) away from CGFloat. If there's
> no way to cheat KVO into doing this sanely, I'll resign myself to it, but I
> kinda hope there's something a little less annoying.
>
> (It's even more annoying because it *was* an NSPoint in a much earlier
> iteration of the code and I changed it because it simplified the code in two
> dozen places, and because the property in question is integer and doesn't
> need the slower floating-point instructions to manipulate it.)
Implement +automaticallyNotifiesObserversForKey: to return NO for that
key, then call will/didChangeValueForKey: yourself in the setter. That
will avoid the expensive automatic KVO machinery, while allowing you
to leave everything else untouched.
Mike
_______________________________________________
Cocoa-dev mailing list (Cocoa-dev@lists.apple.com)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com
This email sent to arch...@mail-archive.com
