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Mina's SocketIoProcessor currently owns a Selector and employs a single Worker to run the NIO "selector loop".
I have been running tests where Im trying to maximise throughput and have found - that in certain multi-cpu environments - this worker thread can encounter a large amount of starvation even though CPU usage is fairly low.
By testing 2 selector-loops instead of 1, I managed to improve my overall test throughput by just under 30%.
The general idea is to do this:
- Each SocketIoProcessor.Worker encapsulates its own work queues associated Selector
- It should be possible to configure the number of Workers (and thus selectors) employed by SocketIoProcessor
- When a SocketSession is added to the SocketIoProcessor, a Worker is selected (round-robin) which will be associated with the SocketSession for its lifetime. This association is managed by SocketSession (get/setWorker)
- When someone asks SocketIoProcessor to do some work to a session, instead of doing it directly, the processor now asks the session for its Worker, and delegates to the worker (i.e, the same worker is always used for an individual session)
I've done some prototyping, and have also checked that the concept works with the latest build.
The prototype is very hacky - mainly because there are some refactoring issues i'd like feed-back on before I submit a "proper" patch for review. Namely:
- How do you want me to tell the SocketIoProcessor how many workers to use? One option is a system property - but thats pretty hacky. I dont think we need to support changing the number of workers after operation has begun (It'll probably be a function of the number of available CPUs) - and this makes the code simpler. However, as SocketIoProcessor is a (non lazy created) singleton, we need a way to get the param in. We could refactor, or maybe introduce a ProcessorOptions class or something. The SocketIoProcessor could interrigate this when initializing. Any direction on your desired approach would be appreciated
Cheers,
Dave
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Improvement
Closed
Minor
Multiple selector loops
