Messages in this thread | | | Date | Fri, 14 Feb 2003 17:50:04 -0800 (PST) | From | Davide Libenzi <> | Subject | Re: Synchronous signal delivery.. |
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On Sat, 15 Feb 2003, Jamie Lokier wrote:
> 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.
POSIX timers might work, and events might be captured using the sigfd() descriptor.
> 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?
What's bad in epoll_wait() to get events from all pollable descriptors ?
- Davide
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