From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [Qemu-devel] Re: [patch uq/master 1/2] virtio-pci: wake up iothread on VIRTIO_PCI_QUEUE_NOTIFY Date: Mon, 22 Feb 2010 17:55:46 +0200 Message-ID: <4B82A902.8090405@redhat.com> References: <20100222135906.347393434@amt.cnet> <20100222140209.878250600@amt.cnet> <4B8292C4.9070802@redhat.com> <20100222142920.GB18992@amt.cnet> <4B829A02.3040605@redhat.com> <20100222151602.GD18992@amt.cnet> <4B82A2CB.3090003@codemonkey.ws> <4B82A375.5000907@redhat.com> <4B82A5E7.2020706@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , qemu-devel@nongnu.org, kvm@vger.kernel.org To: Anthony Liguori Return-path: Received: from mx1.redhat.com ([209.132.183.28]:23218 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753554Ab0BVP4h (ORCPT ); Mon, 22 Feb 2010 10:56:37 -0500 In-Reply-To: <4B82A5E7.2020706@codemonkey.ws> Sender: kvm-owner@vger.kernel.org List-ID: On 02/22/2010 05:42 PM, Anthony Liguori wrote: >>> Spurious calls to qemu_notify_event() also make it difficult to tell >>> when it's actually necessary to call qemu_notify_event() vs. when >>> it's just something that doesn't hurt. >> >> One improvement in this area would be to add a context parameter >> (which eventually resolves to the underlying thread). Currently we'd >> ignore it since we have just one iothread, but it would serve to >> document what's being polled, and later direct the wakeup to the >> correct thread. > > > Ends up looking a lot like a condition. It's not necessarily a bad > thing to model. > But the implementation is very different - condition variables sleep in pthread_cond_wait, the iothread sleeps in poll(). qemu_notify_event() is really requesting iothread t to re-add file fd to its poll set. Maybe we should make this a CharDriverState method. -- error compiling committee.c: too many arguments to function