Re: Accessing array in thread safe way
Re: Accessing array in thread safe way
- Subject: Re: Accessing array in thread safe way
- From: Charles Srstka <email@hidden>
- Date: Thu, 08 Mar 2012 15:20:42 -0600
On Mar 8, 2012, at 2:51 PM, Brian Lambert wrote:
> I should have said, "relatively". As in, good enough for many scenarios where it will be used infrequently and keeping the code simple makes sense.
>
> Of course, you're right, Charles.
>
> 1,000,000 integer increments synchronized by @synchronized, OSSpinLock, and NSLock:
> PerfTimer[95716:403] 1,000,000 @synchronized ++value: [118 ms] [117,813,038 ns]
> PerfTimer[95716:403] 1,000,000 OSSpinLock ++value: [8 ms] [8,444,567 ns]
> PerfTimer[95716:403] 1,000,000 NSLock ++value: [63 ms] [63,049,168 ns]
>
> A million operations in ~100 ms is fast. A million operations in ~10 ms is WICKED fast.
>
> Brian
Another interesting option is mentioned in Apple’s GCD man pages; dispatch_sync can actually be used as a locking mechanism, like so:
__block NSUInteger value = 0;
dispatch_sync(myLockQueue, ^{
value++;
});
This results in something almost as simple as @synchronized, and quite a lot faster. Here are the results I get when running it on my MBP. All my results do take about twice as long as yours; I suspect you have a rather nice machine. :-)
2012-03-08 15:14:56.408 Lock Benchmarks[57369:403] @synchronized value++: 259.156942 ms
2012-03-08 15:14:56.429 Lock Benchmarks[57369:403] OSSpinLock value++: 19.486010 ms
2012-03-08 15:14:56.517 Lock Benchmarks[57369:403] pthread_mutex_t value++: 86.329997 ms
2012-03-08 15:14:56.645 Lock Benchmarks[57369:403] NSLock value++: 127.897978 ms
2012-03-08 15:14:56.692 Lock Benchmarks[57369:403] dispatch_sync value++: 45.979023 ms
Not bad; OSSpinLock is the only thing that seems to be able to best it.
Charles
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