Messages in this thread | | | Date | Sat, 15 Feb 2003 01:01:53 +0000 | From | Jamie Lokier <> | Subject | Re: Synchronous signal delivery.. |
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Davide Libenzi wrote: > > And when that's done you have some nice bonuses: > > > > - All event types are reported equally fast, and in a single > > system call (read()). > > > > - The order in which events occurred is preserved. > > (This is lost when you have to scan multiple queues). > > > > - Hierarchies of event sets of any kind are possible. > > (epoll has solved the logical problems of this already). > > > > - Less code duplicated. > > > > - Adding new kinds of kernel events becomes _very_ simple. > > Hmm ... using read() you'll lose the timeout capability, that IMHO is > pretty nice.
Very good point.
Timeouts could be events too - probably a good idea as they can then be absolute, relative, attached to different system clocks (monotonic vs. timeofday). I think the POSIX timer work is like that.
It seems like a good idea to be able to attach one timeout event in the same system call as the event_read call itself - because it is _so_ common to vary the expiry time every time.
Then again, it is also extremely common to write this:
gettimeofday(...) // calculate time until next application timer expires. // Note also race condition here, if we're preempted. read_events(..., next_app_time - timeofday) // we need to know the current time. gettimeofday(...)
So perhaps the current select/poll/epoll timeout method is not particularly optimal as it is?
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