On Apr 24, 2014, at 8:42 PM, Ken Thomases <k...@codeweavers.com> wrote:
> You may be aware of this, but dispatch_sync() is not necessary or even > particularly relevant to thread-safety. The use of a serial queue or, > possibly, a reader/write mechanism using barriers, is what achieves thread > safety. Initial experimentation showed that dispatch_async was significantly slower than dispatch_sync. This makes sense because dispatch_async has to copy the block (thus allocating an object on the heap and retaining any captured object variables) while dispatch_sync can get away with running the block before the call returns, which avoids all that overhead. > Using a synchronous call is only necessary if your API has synchronous > semantics. For example, if a call provides immediate results to the caller. > Reading from a database would typically have to be synchronous, but writing > to it can often be asynchronous. Yeah, I was torn about making the write calls async. But in the underlying C API both the read and write calls return error codes, since there could be disk or memory errors, and I didn’t want to ignore the return codes on the write functions. (My mama didn’t raise no boys to skip proper error handling.) —Jens _______________________________________________ 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: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
