From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by dpdk.org (Postfix) with ESMTP id 058C9379B for ; Tue, 19 Jul 2016 15:53:32 +0200 (CEST) Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga102.fm.intel.com with ESMTP; 19 Jul 2016 06:53:30 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,389,1464678000"; d="scan'208";a="1024793361" Received: from dpdk06.sh.intel.com ([10.239.129.195]) by fmsmga002.fm.intel.com with ESMTP; 19 Jul 2016 06:53:28 -0700 From: Jianfeng Tan To: dev@dpdk.org Cc: yuanhan.liu@linux.intel.com, zhihong.wang@intel.com, Jianfeng Tan Date: Tue, 19 Jul 2016 13:53:11 +0000 Message-Id: <1468936391-138371-1-git-send-email-jianfeng.tan@intel.com> X-Mailer: git-send-email 2.7.4 Subject: [dpdk-dev] [PATCH] 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: Tue, 19 Jul 2016 13:53:33 -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: 859b480d5afd ("vhost: add guest offload setting") Reported-by: Qian Xu Signed-off-by: Jianfeng Tan --- 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