Bruce M. Simpson wrote:
Hi,
I looked at ACE years and years ago (~1997) when Doug Schmidt was first
promoting the ideas behind it. The whole Reactor/Proactor split pretty
much hangs on the event dispatch which your particular OS supports.
The key observation is whether your target OS implements events in an
edge-triggered or level-triggered way; I am borrowing definitions from
electronic engineering here.
You could do a straight port with Proactor, but performance will
probably suck, because both FreeBSD (and Linux, I believe) need to
emulate POSIX asynchronous I/O operations.
Reactor will generally "fare better" on UNIX derived systems such as
FreeBSD and Linux, because its event handling primitives are geared
towards the level-triggered facilities provided by select().
A true FreeBSD port would use kevent with AIO.
At Cisco/ironport we use AIO with the build in kevent trigering to
great effect. Certainly for sockets it works VERY well.
In Windows, Winsock events use asynchronous notifications which may be
tied to Win32 EVENT objects, and the usual Kernel32.DLL thread
primitives are used around this. This makes Proactor more appropriate in
that environment.
XORP does some similar stuff to ACE under the hood to support the native
socket facilities of both Windows and FreeBSD/Linux. It's hybridized but
it behaves more like Reactor because we run in a single thread, and you
have to force Winsock's helper thread to run, by preempting you, using
some file handle and socket tricks.
I don't currently know about stability of ACE on FreeBSD.
cheers
BMS
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