Re: dispatch_async Performance Issues
Re: dispatch_async Performance Issues
- Subject: Re: dispatch_async Performance Issues
- From: Jonathan Taylor <email@hidden>
- Date: Tue, 28 Jun 2011 15:07:43 +0100
... and more importantly I do not believe your code makes correct use of dispatch_group_async. Your first call adds a producer block to the global concurrent queue, which may start executing immediately. At some time soon afterwards you add a consumer block to the global concurrent queue, which again may start executing immediately - while the producer block is still in the process of "producing". As far as I can see the code appears to have a number of major issues:
1. Theoretically your producer block may not have produced anything by the time your consumer block executes
2. What happens if your consumer block has processed all the currently-added blocks before the producer block has added the eof marker?
3. You have only one single consumer block, which means you will only have a single consumer "thread" running under Grand Central Dispatch, which rather defeats the purpose of using it at all! I think you may not have fully understood how GCD is intended to be used...
4. Are you sure that your mysterious and rather complicated-seeming CFDataConstBuffers class is sufficiently threadsafe for your producer to be adding to it at the same time as your consumer block is iterating through it? I am 99% sure that the "explicit" consumer code you wrote in ConcurrentProduceConsume is not threadsafe.
Jonny._______________________________________________
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