From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH v11 6/6] virtio-balloon: VIRTIO_BALLOON_F_CMD_VQ Date: Tue, 20 Jun 2017 19:18:46 +0300 Message-ID: <20170620190343-mutt-send-email-mst@kernel.org> References: <1497004901-30593-1-git-send-email-wei.w.wang@intel.com> <1497004901-30593-7-git-send-email-wei.w.wang@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii 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, david@redhat.com, dave.hansen@intel.com, cornelia.huck@de.ibm.com, akpm@linux-foundation.org, mgorman@techsingularity.net, aarcange@redhat.com, amit.shah@redhat.com, pbonzini@redhat.com, liliang.opensource@gmail.com To: Wei Wang Return-path: Content-Disposition: inline In-Reply-To: <1497004901-30593-7-git-send-email-wei.w.wang@intel.com> Sender: owner-linux-mm@kvack.org List-Id: kvm.vger.kernel.org On Fri, Jun 09, 2017 at 06:41:41PM +0800, Wei Wang wrote: > - if (!virtqueue_indirect_desc_table_add(vq, desc, num)) { > + if (!virtqueue_indirect_desc_table_add(vq, desc, *num)) { > virtqueue_kick(vq); > - wait_event(vb->acked, virtqueue_get_buf(vq, &len)); > - vb->balloon_page_chunk.chunk_num = 0; > + if (busy_wait) > + while (!virtqueue_get_buf(vq, &len) && > + !virtqueue_is_broken(vq)) > + cpu_relax(); > + else > + wait_event(vb->acked, virtqueue_get_buf(vq, &len)); This is something I didn't previously notice. As you always keep a single buffer in flight, you do not really need indirect at all. Just add all descriptors in the ring directly, then kick. E.g. virtqueue_add_first virtqueue_add_next virtqueue_add_last ? You also want a flag to avoid allocations but there's no need to do it per descriptor, set it on vq. -- MST -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org