Messages in this thread | | | From | Zach Brown <> | Subject | Re: [patch] aio: add per task aio wait event condition | Date | Tue, 2 Jan 2007 18:06:25 -0800 |
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On Jan 2, 2007, at 5:50 PM, Chen, Kenneth W wrote:
> Zach Brown wrote on Tuesday, January 02, 2007 5:24 PM >>> That is not possible because when multiple tasks waiting for >>> events, they >>> enter the wait queue in FIFO order, prepare_to_wait_exclusive() does >>> __add_wait_queue_tail(). So first io_getevents() with min_nr of 2 >>> will be woken up when 2 ops completes. >> >> So switch the order of the two sleepers in the example? > > Not sure why that would be a problem though: whoever sleep first will > be woken up first.
Why would the min_nr = 3 sleeper be woken up in that case? Only 2 ios were issued.
Maybe the app was relying on the min_nr = 2 completion to issue 3 more ios for the min_nr = 3 sleeper, who knows.
> Before I challenge that semantics, I want to mention that in current > implementation, dribbling AIO events will be distributed in round > robin > fashion to all pending tasks waiting in io_getevents.
Yeah, don't misunderstand me -- we agree that the current situation is bad.
> In the example you > gave earlier, task with min_nr of 2 will be woken up after 4 completed > events.
I only gave 2 ios/events in that example.
Does that clear up the confusion?
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