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djmarcus

djmarcus djmarcus

Niner since 2011

  • AppFabric.tv - Threading with Jeff Richter

    @JeffRichter:

    I thought I was familiar with the AsyncEnumerator class.. but apparently I am not.I will take a closer look.

    Being able to 'resume execution' at the point of I/O with the stack intact and the same as it was prior to the I/O is exactly what I was referring to.

    Thanks for your quick reply.

    -David

  • AppFabric.tv - Threading with Jeff Richter

    @JeffRichter:

    Hi

    Great video... I enjoyed it.

    Yet I think you glossed over the real reason people use threads. Unless an application has been designed from its inception to be asynchronous, threading does one thing that begin/end asynch does not: it preserves application state through the stack.

    In particular, imagine a legacy application that is deep down in its stack of A calling B calling C calling ... and somewhere deep in the stack it needs to do an I/O.

    If it can't proceed until the I/O is done there is little to do but block (which is why you need to be on a thread, otherwise the whole application freezes).

    If you spawned an asynch request at this point, what is the thread supposed to do until the I/O is done? It can't just return !!

    I wish you had addressed this point - in my opinion it is the key issue regarding threading.

    The answer, I believe, is to have the stack be independent of threading of execution (which is after all just a way of sharing the CPU across multiple logical work requests). A call stack represents the true application state (along with the heap, ...).

    In this model of an application thread, it is the stack that is important. When a 'stack' is blocked the underlying execution (managed by the system) can just jump to another 'stack'.

    I think this is what tasks are all about, no?

    -David