Hi Jody, --- Jody Hagins <jody-boost-011304@atdesk.com> wrote: <snip>
I took a brief look at the epoll implementation. I don't see EPOLLET anywhere, so you are doing Level Triggered. Curious why not Edge Triggered? I imagine the reason is to prevent the implementation from having to either keep track of the FD still being ready (until EAGAIN) or keeping its own internal buffer to hold the "overflow" but I'm still curious. It seems a framework like this is good for ET since it can take care of the added complexities.
When I first added epoll support it was to meet the requirements of handling tens of thousands of connections. I used the level-triggered interface because it mapped easily from the existing select_reactor implementation. However, I have already been thinking about converting to use edge-triggered epoll to reduce the number of epoll_ctl calls. Some recent changes I have made post-review-version are steps in this direction. <snip>
However, of some concern is the fact that you call epoll_wait() from multiple threads using the same epoll fd.
Actually epoll_wait is only called from one thread at a time. This coordination is managed by the task_demuxer_service. <snip>
Also, it seems a waste to call epoll_ctl() after each I/O operation, regardless of whether it will change the events.
Yep, using edge-triggered epoll should take care of this.
Before I severely overstep, can you point me to a good example of async_read operations? I see this as a the primary use case, yet it does not appear in any of the tutorials.
Yeah, good point! I should add tutorials that demonstrate more complex interactions. Maybe have a look at the chat or serialization examples, since the message format used in these programs is a fixed length header followed by a body.
async_read() does not provide the buffer to the handler. It seems the only way to use it is with a function object that contains the buffer. Is that a correct understanding, or do I just need to go back to sleep?
Binding it into the function object is one way. But often this binding is indirect, in the sense that you bind a this pointer and the buffer is a data member of the class. Cheers, Chris