From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by dpdk.org (Postfix) with ESMTP id 068BD2B8E for ; Thu, 21 Jul 2016 02:23:58 +0200 (CEST) Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga103.jf.intel.com with ESMTP; 20 Jul 2016 17:23:56 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,396,1464678000"; d="scan'208";a="1020933373" Received: from dpdk06.sh.intel.com ([10.239.129.195]) by orsmga002.jf.intel.com with ESMTP; 20 Jul 2016 17:23:54 -0700 From: Jianfeng Tan To: dev@dpdk.org Cc: yuanhan.liu@linux.intel.com, zhihong.wang@intel.com, qian.q.xu@intel.com, Jianfeng Tan Date: Thu, 21 Jul 2016 00:23:37 +0000 Message-Id: <1469060617-50465-1-git-send-email-jianfeng.tan@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1468936391-138371-1-git-send-email-jianfeng.tan@intel.com> References: <1468936391-138371-1-git-send-email-jianfeng.tan@intel.com> Subject: [dpdk-dev] [PATCH v2] examples/vhost: fix perf regression 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: Thu, 21 Jul 2016 00:23:59 -0000 We find significant perfermance drop introduced by below commit, when vhost example is started with --mergeable 0 and inside vm, kernel virtio-net driver is used to do ip based forwarding. The root cause is that below commit adds support for VIRTIO_NET_F_GUEST_TSO4 and VIRTIO_NET_F_GUEST_TSO6, and when mergeable is disabled, it triggers big_packets path of virtio-net driver. In this path, virtio driver uses 19 desc with 18 4K-sized pages to receive each packet, so that it can receive a big packet with size of 64K. But QEMU only creates 256 desc entries for each vq, which results in that only 13 packets can be received. VM kernel can quickly handle those packets and go to sleep (HLT). As QEMU has no option to set the desc entries of a vq, so here, we disable VIRTIO_NET_F_GUEST_TSO4 and VIRTIO_NET_F_GUEST_TSO6 with VIRTIO_NET_F_HOST_TSO4 and VIRTIO_NET_F_HOST_TSO6 when we disable tso of vhost example, to avoid VM kernel virtio driver go into big_packets path. Fixes: 9fd72e3cbd29 ("examples/vhost: add virtio offload") Reported-by: Qian Xu Signed-off-by: Jianfeng Tan --- v2: change the Fixes line to point to proper commit to fix. examples/vhost/main.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/examples/vhost/main.c b/examples/vhost/main.c index 3b98f42..92a9823 100644 --- a/examples/vhost/main.c +++ b/examples/vhost/main.c @@ -327,6 +327,8 @@ port_init(uint8_t port) if (enable_tso == 0) { rte_vhost_feature_disable(1ULL << VIRTIO_NET_F_HOST_TSO4); rte_vhost_feature_disable(1ULL << VIRTIO_NET_F_HOST_TSO6); + rte_vhost_feature_disable(1ULL << VIRTIO_NET_F_GUEST_TSO4); + rte_vhost_feature_disable(1ULL << VIRTIO_NET_F_GUEST_TSO6); } rx_rings = (uint16_t)dev_info.max_rx_queues; -- 2.7.4