From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [119.145.14.66]) by dpdk.org (Postfix) with ESMTP id B096F9A81 for ; Tue, 24 Mar 2015 02:00:10 +0100 (CET) Received: from 172.24.2.119 (EHLO szxeml431-hub.china.huawei.com) ([172.24.2.119]) by szxrg03-dlp.huawei.com (MOS 4.4.3-GA FastPath queued) with ESMTP id BDN47322; Tue, 24 Mar 2015 09:00:07 +0800 (CST) Received: from [127.0.0.1] (10.177.19.115) by szxeml431-hub.china.huawei.com (10.82.67.208) with Microsoft SMTP Server id 14.3.158.1; Tue, 24 Mar 2015 09:00:02 +0800 Message-ID: <5510B709.5030907@huawei.com> Date: Tue, 24 Mar 2015 08:59:53 +0800 From: Linhaifeng User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:31.0) Gecko/20100101 Thunderbird/31.1.0 MIME-Version: 1.0 To: "Xie, Huawei" References: <1426925237-8312-1-git-send-email-haifeng.lin@huawei.com> <551005DD.4060508@huawei.com> In-Reply-To: Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.19.115] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020203.5510B717.0125, ss=1, re=0.001, recu=0.000, reip=0.000, cl=1, cld=1, fgs=0, ip=0.0.0.0, so=2013-05-26 15:14:31, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: ec9c3ed1220b0e0fe86c9649e880ae88 Cc: "dev@dpdk.org" Subject: Re: [dpdk-dev] [PATCH] cast used->idx to volatile X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 24 Mar 2015 01:00:12 -0000 On 2015/3/23 20:54, Xie, Huawei wrote: > > >> -----Original Message----- >> From: Linhaifeng [mailto:haifeng.lin@huawei.com] >> Sent: Monday, March 23, 2015 8:24 PM >> To: dev@dpdk.org >> Cc: Ouyang, Changchun; Xie, Huawei >> Subject: Re: [dpdk-dev] [PATCH] cast used->idx to volatile >> >> >> >> On 2015/3/21 16:07, linhaifeng wrote: >>> From: Linhaifeng >>> >>> Same as rte_vhost_enqueue_burst we should cast used->idx >>> to volatile before notify guest. >>> >>> Signed-off-by: Linhaifeng >>> --- >>> lib/librte_vhost/vhost_rxtx.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c >>> index 535c7a1..8d674d1 100644 >>> --- a/lib/librte_vhost/vhost_rxtx.c >>> +++ b/lib/librte_vhost/vhost_rxtx.c >>> @@ -722,7 +722,7 @@ rte_vhost_dequeue_burst(struct virtio_net *dev, >> uint16_t queue_id, >>> } >>> >>> rte_compiler_barrier(); >>> - vq->used->idx += entry_success; >>> + *(volatile uint16_t *)&vq->used->idx += entry_success; > > > Haifeng: > We have compiler barrier before and an external function call behind, so we don't need volatile here. > Do you meet issue? > Tx_q is sometimes stopped when we use virtio_net. Because vhost thought there are no buffers in tx_q and virtio_net though vhost haven't handle all packets so we have to restart VM to restore work. The status in VM is: Mar 18 17:11:10 linux-b2ij kernel: [46337.246687] net eth7: virtnet_poll Mar 18 17:11:10 linux-b2ij kernel: [46337.246690] net eth7: receive_buf Mar 18 17:11:10 linux-b2ij kernel: [46337.246693] net eth7: vi->num=239 Mar 18 17:11:10 linux-b2ij kernel: [46337.246695] net eth7: svq:avail->idx=52939 used->idx=52939 num_free=18 num_added=0 svq->last_used_idx=52820 Mar 18 17:11:10 linux-b2ij kernel: [46337.246699] net eth7: rvq:avail->idx=36215 used->idx=35977 num_free=18 num_added=0 rvq->last_used_idx=35977 Mar 18 17:11:11 linux-b2ij kernel: [46337.901038] net eth7: dev_queue_xmit, qdisc->flags=4, qdisc->state deactiveed=0 Mar 18 17:11:12 linux-b2ij kernel: [46337.901042] net eth7: dev_queue_xmit, txq->state=1, stopped=1 Why compiler barrier not take effect in our case? Is compiler barrier depended on -O3 option? We use -O2 option. >>> /* Kick guest if required. */ >>> if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)) >>> eventfd_write((int)vq->callfd, 1); >>> >> >> -- >> Regards, >> Haifeng > > > -- Regards, Haifeng