From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752370AbeAXFpT (ORCPT ); Wed, 24 Jan 2018 00:45:19 -0500 Received: from mga09.intel.com ([134.134.136.24]:55188 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750992AbeAXFpS (ORCPT ); Wed, 24 Jan 2018 00:45:18 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,405,1511856000"; d="scan'208";a="168676516" Message-ID: <5A681E03.1030007@intel.com> Date: Wed, 24 Jan 2018 13:47:47 +0800 From: Wei Wang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: "Michael S. Tsirkin" CC: virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-mm@kvack.org, mhocko@kernel.org, akpm@linux-foundation.org, pbonzini@redhat.com, liliang.opensource@gmail.com, yang.zhang.wz@gmail.com, quan.xu0@gmail.com, nilal@redhat.com, riel@redhat.com Subject: Re: [PATCH v23 2/2] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ References: <1516762227-36346-1-git-send-email-wei.w.wang@intel.com> <1516762227-36346-3-git-send-email-wei.w.wang@intel.com> <20180124064923-mutt-send-email-mst@kernel.org> In-Reply-To: <20180124064923-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/24/2018 01:01 PM, Michael S. Tsirkin wrote: > On Wed, Jan 24, 2018 at 10:50:27AM +0800, Wei Wang wrote: > This will not DTRT in all cases. It's quite possible > that host does not need the kick when ring is half full but > does need it later when ring is full. > You can kick at ring half full as optimization but you absolutely > still must kick on ring full. Something like: > > if (vq->num_free == virtqueue_get_vring_size(vq) / 2 || > vq->num_free <= 2) Right. Would "if (vq->num_free < virtqueue_get_vring_size(vq) / 2" be better? Best, Wei