> 1) It has no facility for timer events Yup, it's on the todo list.
> 2) It's tied to file descriptors (only a problem for win32) The other way round: it's not tied to file descriptors for win32, which is already a problem for e.g. networked backends. main-loop.c has the code that is needed, but it's low on the todo list. Note that tap-win32 for example doesn't need this. > 3) The fd support is tied to read/write without an extensibility > mechanism for other fd events Yes. Though internally it uses g_poll, so it's "just" a matter of defining the right API. > 4) It's got no mechanism to interact with signals signalfd? (GSource doesn't have any such mechanism directly). > 5) It's not obvious how we would integrate with polling-based > callbacks like we have in the character layer and networking layer. Isn't io_flush one such mechanism? Right now it applies to both io_read and io_write, but really it is never used for io_write. Also, this and (3) might be the same problem. > So I agree it's simple but I don't think it can reasonably stay simple. > I think if we added all of the above, the best we would expect to end > up with is something that looked like glib. > > As it stands, the lack of (5) would make it extremely difficult to > convert the networking layer. Quite possible, I've never looked very much at the networking layer. Paolo > Regards, > > Anthony Liguori > > > > >>> and AioContext's code is vastly simpler than GMainLoop's. > >> > >> For now. > > > > Fair enough. :) > > > >>> AioContext is also documented and unit tested, with tests > >>> for both standalone and GSource operation. Unit tests for > >>> AioContext > >>> users are trivial to write, we have one in test-thread-pool. > >>> > >>>> Did you have a specific concern with using glib vs. AioContext? > >>>> Is it > >>>> about reusing code in the block layer where AioContext is > >>>> required? > >>> > >>> In the short term yes, code duplication is a concern. We already > >>> have > >>> two implementation of virtio. > >> > >> I share your concern but in the opposite direction. We have three > >> main > >> loops today. > > > > Yes, and two of them (main-loop.c/qemu-timer.c and async.c) can be > > merged. > > > >>> I would like the dataplane virtio code to > >>> grow everything else that needs to be in all dataplane-style > >>> devices > >>> (for example, things such as setting up the guest<->host > >>> notifiers), and > >>> the hw/virtio.c API implemented on top of it (or dead > >>> altogether). > >>> Usage of AioContext is pretty much forced by the block layer. > >> > >> I don't think that AioContext is the right answer because it makes > >> it > >> too easy to shoot yourself in the foot. > > > > See above, if nesting is the problem it's gone. > > > > Paolo >