From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57097) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZaM5E-0002Fx-Kk for qemu-devel@nongnu.org; Fri, 11 Sep 2015 07:01:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZaM5D-0005ko-L5 for qemu-devel@nongnu.org; Fri, 11 Sep 2015 07:01:32 -0400 Date: Fri, 11 Sep 2015 19:01:22 +0800 From: Fam Zheng Message-ID: <20150911110122.GC9241@ad.nay.redhat.com> References: <20150729115333.GA15022@ad.nay.redhat.com> <55B8C12D.2070105@redhat.com> <20150909032205.GA10922@ad.nay.redhat.com> <55F28D99.5060908@redhat.com> <20150911091433.GA6759@ad.nay.redhat.com> <20150911094425.GA9241@ad.nay.redhat.com> <55F2A4D6.6050009@redhat.com> <20150911104055.GB9241@ad.nay.redhat.com> <55F2B0EE.7030407@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55F2B0EE.7030407@redhat.com> Subject: Re: [Qemu-devel] [Qemu-block] [PATCH v2 11/11] block: Only poll block layer fds in bdrv_aio_poll List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: kwolf@redhat.com, qemu-block@nongnu.org, Alberto Garcia , qemu-devel@nongnu.org, stefanha@redhat.com 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()? Fam