Re: performance problem with IORegistryEntryCreateCFProperties
Re: performance problem with IORegistryEntryCreateCFProperties
- Subject: Re: performance problem with IORegistryEntryCreateCFProperties
- From: "Herb Petschauer" <email@hidden>
- Date: Tue, 9 Dec 2008 09:01:41 -0800
Out of curiosity, why spawn a second thread to poll when you can use
IOServiceAddMatchingNotification() [and friends, search in
/Developer/Examples] to get you notifications of devices appearing and
disappearing? That is going to faster than walking the entire
IORegistry every time to find the matches which is effectively what
IOServiceGetMatchingServices() is going to be doing [do an "ioreg -l"
in Terminal window to get the full list]
Cheers,
-H.
2008/12/8 Brad Justice <email@hidden>:
> My application spawns a POSIX background thread that polls for certain
> hardware changes. I have found that according to Activity Monitor and BigTop
> it is consuming about 5% of the CPU, which seems inexplicable to me.
>
> The thread loop calls sleep(2) and then begins its checks. Setting Activity
> Monitor granularity to 0.5 seconds, I find that every 4 periods the thread
> consumes 20% of the CPU, and 0 % for the other three. By commenting out
> sections of code, I have isolated the CPU usage to one loop that executes 7
> times. I have confirmed the number of iterations by single stepping in the
> debugger.In particular, the execution of seven paired calls to
> IORegistryEntryCreateCFProperties and CFRelease result in 5% CPU usage on my
> MacBook Pro according to my tools.
>
> Am I misinterpreting my tools, is this an Activity Monitor bug, or are
> IORegistryEntryCreateCFProperties and CFRelease heavily CPU intensive for
> some reason? It seems to me seven calls every two seconds should not
> register activity at this level.
>
> Thanks for any advice that you can provide. Source for the offending loop
> below.
>
> classToMatch = IOServiceMatching (kIOHIDDeviceKey);
> if (classToMatch)
> { numberRef = NULL; mach_port_t mport =
> [myList getMasterport];
> result =
> IOServiceGetMatchingServices(mport,classToMatch,&iterator);
> if (KERN_SUCCESS == result) {
> if(iterator)
> {
> while( ( serviceObject = IOIteratorNext ( iterator ) ) )
> {
> CFMutableDictionaryRef hidProperties = 0;
> result = IORegistryEntryCreateCFProperties
> (serviceObject, &hidProperties, kCFAllocatorDefault, kNilOptions);
> if (result == KERN_SUCCESS)
> {
> serialNumberValue = (NSString *)
> CFDictionaryGetValue(hidProperties,CFSTR("SerialNumber"));
> if (serialNumberValue != NULL)
> {
> range = [serialNumberValue
> rangeOfString:matchingString];
> if (range.length != 0)
> {
> count++;
> }
> }
> }
> CFRelease(hidProperties);
> }
> IOObjectRelease(iterator);
> } } }
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