[erlang-questions] driver asyncronous notifications
Fri Jun 1 13:08:41 CEST 2007
Serge Aleynikov wrote:
> Oscar Hellström wrote:
>> Could you use a pipe here to notify the emulator of the event?
> Indeed I described that solution in the previous email as well:
> >> One possibility is to create a pipe and
> >> register a read-end of the pipe with Erlang's select loop by calling
> >> driver_select() function, and use write() call on the other end of
> >> the pine from another thread to communicate some activity, so that if
> >> would trigger the ready_input() driver's callback in the context of
> >> emulator's thread. However this is a very expensive solution which I
> >> wouldn't want to use.
I should really learn to think before I speak as well as read before I
> The problem here is that pipe is a very expensive way of doing
> inter-thread communications. I implemented this approach and wasn't
> happy with performance (that involved two context switches and an
> expensive select() call for messages communicated to the emulator's
> thread). I wish that there was something much more light-weight to
> notify emulator's thread of an external non I/O related event.
Have you compared the performance loss to that of a port driver? A port
driver would also have to communicate through a pipe, but the
synchronisation issues should be gone. Also, the emulator should be able
to use kernel polling the fd:s I guess.
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