On Fri, 09/11 13:02, Paolo Bonzini wrote: > > > On 11/09/2015 13:01, Fam Zheng wrote: > > On Fri, 09/11 12:46, Paolo Bonzini wrote: > >> > >> > >> On 11/09/2015 12:40, Fam Zheng wrote: > >>> On Fri, 09/11 11:54, Paolo Bonzini wrote: > >>>> > >>>> > >>>> On 11/09/2015 11:44, Fam Zheng wrote: > >>>>>>>> That would be a step back. Using GSource is useful because it lets > >>>>>>>> you integrate libraries such as GTK+. > >>>>>>> > >>>>>>> Can we move GTK to a separate GSource thread? > >>>>>> > >>>>>> I think that GTK should always run in the main thread, or at least the > >>>>>> one running the default main loop / GMainContext. > >>>>> > >>>>> Yeah it's basically GMainContext staying in the main thread and > >>>>> block/net/chardev I/O put in a new AioContext thread. > >>>> > >>>> Why? The point of an event loop is that you can multiplex everything on > >>>> the same thread. Unless we have specific needs (e.g. scalability) one > >>>> thread is the way to go and keep things simple. > >>> > >>> The reason is scalability. :) > >> > >> Scalability of what? If virtio-net or virtio-serial needs to be more > >> scalable, putting all of them into a non-main-loop thread will not make > >> things more scalable, because you have a single thread anyway. You'd > >> need to go BQL-free and allow an arbitrary number. > >> > >>> Moving things to AIO isn't deviation, it's more about enabling of > >>> dataplane and > >>> epoll. That's why block was moved to AioContext, and I think we can do > >>> similar > >>> for net and serial, the difference is that as a start, they don't need to > >>> be > >>> fully BQL-free like virtio-blk and scsi. But by running in an aio_poll() > >>> loop, > >>> they can better performance because of epoll. > >> > >> Isn't that what your "iohandler.c with AioHandler" already does? True, > >> it would be epoll-within-poll, not pure poll. But if you need epoll, > >> you might as well go BQL-free. > > > > epoll-within-poll? Do you mean change the main event loop from: > > > > qemu_poll_ns([..., ioeventfd1, ioeventfd2, ..., ioeventfd99], ...) > > > > to > > > > qemu_poll_ns([epollfd], ...) > > > > where epollfd watches all the fds, and let the handler of epollfd do > > epoll_wait()? > > I mean that glib's main loop (or os_host_main_loop_wait in main-loop.c) > uses poll, and then the AioContext GSource uses epoll. Still, you have > a constant (and low) number of file descriptors in the outer poll. >
OK, I think I get your idea, and it sounds good to me, thank you very much! ;-) Fam
