From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Wang Subject: Re: [PATCH v14 3/5] virtio-balloon: VIRTIO_BALLOON_F_SG Date: Fri, 18 Aug 2017 15:39:27 +0800 Message-ID: <599699AF.1090705@intel.com> References: <1502940416-42944-1-git-send-email-wei.w.wang@intel.com> <1502940416-42944-4-git-send-email-wei.w.wang@intel.com> <20170818051451-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-mm@kvack.org, mhocko@kernel.org, akpm@linux-foundation.org, mawilcox@microsoft.com, david@redhat.com, cornelia.huck@de.ibm.com, mgorman@techsingularity.net, aarcange@redhat.com, amit.shah@redhat.com, pbonzini@redhat.com, willy@infradead.org, liliang.opensource@gmail.com, yang.zhang.wz@gmail.com, quan.xu@aliyun.com To: "Michael S. Tsirkin" Return-path: Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: In-Reply-To: <20170818051451-mutt-send-email-mst@kernel.org> List-Id: kvm.vger.kernel.org On 08/18/2017 10:22 AM, Michael S. Tsirkin wrote: > +static void send_balloon_page_sg(struct virtio_balloon *vb, > + struct virtqueue *vq, > + void *addr, > + uint32_t size) > +{ > + unsigned int len; > + int ret; > + > + do { > + ret = add_one_sg(vq, addr, size); > + virtqueue_kick(vq); > + wait_event(vb->acked, virtqueue_get_buf(vq, &len)); > + /* > + * It is uncommon to see the vq is full, because the sg is sent > + * one by one and the device is able to handle it in time. But > + * if that happens, we go back to retry after an entry gets > + * released. > + */ > Why send one by one though? Why not batch some s/gs and wait for all > of them to be completed? If memory if fragmented, waiting every time is > worse than what we have now (VIRTIO_BALLOON_ARRAY_PFNS_MAX at a time). > OK, I'll do batching in some fashion. Best, Wei