make scheduler support batch process for certain task

[wsky]

some kind of task is lightweight and has many,

process one task per thread will course large cost at thread switch, threadpool size will alwasy not enough.

so, we need batch them, process more than one task per thread

[wsky]

39

[wsky]

endpoint should support schedule certain type of task by msg.messageType

https://github.com/wsky/top-link/blob/c6fdce2b16aa9c3a715b9669ea0331c6d2ca891e/java/src/main/java/com/taobao/top/link/endpoint/EndpointChannelHandler.java#L143

// dispatch
        this.scheduler.schedule(msgFrom, new Runnable() {
            @Override
            public void run() {
                try {
                    internalOnMessage(context, msg, msgFrom);
                } catch (LinkException e) {
                    logger.error(e);
                }
            }
        });

[wsky]

scheduler's job looks like actor does. :)

[wsky]

TODO: test perf on batched lightweight task

[wsky]

37

[wsky]

in EndpointPerf test, using BatchedScheduler, server will have low cpu cost, but if batchSize is so large, 1000, client got execution timeout

[wsky]

in some case, it's about balance problem, that server have fixed biz threadpool, 400 e.g.

lightweight request maybe fill them at moment, then other request maybe hold or reject, batch maybe make it more balanced,

or, maybe we need add different thread pool for differentr request, make it easy.

[wsky]

if we provided async io operation to task, like nix_lua coroutine does,