CompositeSubscription with atomic field updater #1236
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RxJava-pull-requests #1137 SUCCESS |
| if (oldState.isUnsubscribed) { | ||
| return; | ||
| } | ||
| // intrinsics may make this a single instruction and may prevent concurrent add/remove faster |
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For my education can you explain what you mean by this comment?
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On x86 and with Java 8, getAndSet is compiled to LOCK XCHG instead of looping and trying to CAS in the new value. This may be true for other platforms. Since now the swap-in of the terminal state is fully atomic, concurrently running add or remove loops will stop faster. Previously, since everybody looped, it was more likely an add succeded before unsubscribe did. This might not be of concern just I wanted to explain the reason behind the use of getAndSet here.
benjchristensen
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May 21, 2014
CompositeSubscription with atomic field updater
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This PR is aimed at #1204 to reduce unnecessary memory overhead in frequently used classes. This change in
CompositeSubscriptionsaves about 24 bytes per instance.In addition, the field updaters may be faster by about 8-15% for small adds and removals. I've changed the implementation of unsubscribe to use getAndSet which leverages platform intrinsics and is usually compiled to a single instruction: this makes unsubscribing a tiny bit faster and thus reducing latency in benchmarks that only pass on single element around.