From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41603) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZKQ5g-0004Gk-Np for qemu-devel@nongnu.org; Wed, 29 Jul 2015 08:04:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZKQ5f-0001pb-UI for qemu-devel@nongnu.org; Wed, 29 Jul 2015 08:04:08 -0400 References: <1438144934-23619-1-git-send-email-famz@redhat.com> <1438144934-23619-12-git-send-email-famz@redhat.com> <55B882C1.8070500@redhat.com> <20150729105725.GA10376@ad.nay.redhat.com> <55B8B2C3.9050307@redhat.com> <20150729115333.GA15022@ad.nay.redhat.com> From: Paolo Bonzini Message-ID: <55B8C12D.2070105@redhat.com> Date: Wed, 29 Jul 2015 14:03:57 +0200 MIME-Version: 1.0 In-Reply-To: <20150729115333.GA15022@ad.nay.redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [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: Fam Zheng Cc: kwolf@redhat.com, stefanha@redhat.com, qemu-devel@nongnu.org, qemu-block@nongnu.org On 29/07/2015 13:53, Fam Zheng wrote: >> > Yes, though I think you'd end up reverting patches 10 and 11 in the end. > We will add outer disable/enable pairs to prevent another threads's aio_poll > from sneaking in between bdrv_aio_poll calls, but we needn't obsolete > bdrv_aio_poll() because of that - it can be useful by itself. For example > bdrv_aio_cancel shouldn't look at ioeventfd, otherwise it could spin for too > long on high load. Does that make sense? Did you mean bdrv_drain() (when it is not already surrounded by disable/enable pairs in the caller)? But yes, that makes sense. I'm not sure that it makes sense to disable/enable in places such as bdrv_pread. The caller's block, if any, should suffice. In this sense you'd end up reverting large parts of patch 10. Then you would have to see how many calls to bdrv_aio_poll are still there, and how many can be converted with no semantic change to aio_poll (e.g. there's no difference in qemu-img.c), and you'd end up reverting patches 9 and 11 too. But we can look at that later. Paolo