From patchwork Tue Aug 30 03:36:04 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhihong Wang X-Patchwork-Id: 15546 X-Patchwork-Delegate: yuanhan.liu@linux.intel.com Return-Path: X-Original-To: patchwork@dpdk.org Delivered-To: patchwork@dpdk.org Received: from [92.243.14.124] (localhost [IPv6:::1]) by dpdk.org (Postfix) with ESMTP id AE0BC5584; Tue, 30 Aug 2016 12:44:18 +0200 (CEST) Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by dpdk.org (Postfix) with ESMTP id 9214B4A65 for ; Tue, 30 Aug 2016 12:44:05 +0200 (CEST) Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga103.fm.intel.com with ESMTP; 30 Aug 2016 03:44:04 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.30,255,1470726000"; d="scan'208";a="2723022" Received: from unknown (HELO dpdk5.sh.intel.com) ([10.239.129.118]) by orsmga004.jf.intel.com with ESMTP; 30 Aug 2016 03:44:03 -0700 From: Zhihong Wang To: dev@dpdk.org Cc: maxime.coquelin@redhat.com, yuanhan.liu@linux.intel.com, thomas.monjalon@6wind.com, Zhihong Wang Date: Mon, 29 Aug 2016 23:36:04 -0400 Message-Id: <1472528164-54296-7-git-send-email-zhihong.wang@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1472528164-54296-1-git-send-email-zhihong.wang@intel.com> References: <1471319402-112998-1-git-send-email-zhihong.wang@intel.com> <1472528164-54296-1-git-send-email-zhihong.wang@intel.com> Subject: [dpdk-dev] [PATCH v4 6/6] vhost: optimize cache access 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: , Errors-To: dev-bounces@dpdk.org Sender: "dev" This patch reorders the code to delay virtio header write to optimize cache access efficiency for cases where the mrg_rxbuf feature is turned on. It reduces CPU pipeline stall cycles significantly. --- Changes in v3: 1. Remove unnecessary memset which causes frontend stall on SNB & IVB. 2. Rename variables to follow naming convention. Signed-off-by: Zhihong Wang --- lib/librte_vhost/vhost_rxtx.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c index ddc7b21..fc5dc4a 100644 --- a/lib/librte_vhost/vhost_rxtx.c +++ b/lib/librte_vhost/vhost_rxtx.c @@ -196,6 +196,7 @@ enqueue_packet(struct virtio_net *dev, struct vhost_virtqueue *vq, uint32_t mbuf_len; uint32_t mbuf_avail; uint32_t copy_len; + uint32_t copy_virtio_hdr; uint32_t extra_buffers = 0; /* start with the first mbuf of the packet */ @@ -210,12 +211,12 @@ enqueue_packet(struct virtio_net *dev, struct vhost_virtqueue *vq, if (unlikely(!desc_addr)) goto error; - /* handle virtio header */ + /* + * handle virtio header, the actual write operation is delayed + * for cache optimization, to reduce CPU pipeline stall cycles. + */ virtio_hdr = (struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)desc_addr; - virtio_enqueue_offload(mbuf, &(virtio_hdr->hdr)); - if (is_mrg_rxbuf) - virtio_hdr->num_buffers = extra_buffers + 1; - + copy_virtio_hdr = 1; vhost_log_write(dev, desc->addr, dev->vhost_hlen); PRINT_PACKET(dev, (uintptr_t)desc_addr, dev->vhost_hlen, 0); desc_offset = dev->vhost_hlen; @@ -266,8 +267,15 @@ enqueue_packet(struct virtio_net *dev, struct vhost_virtqueue *vq, goto error; } - /* copy mbuf data */ + /* copy virtio header and mbuf data */ copy_len = RTE_MIN(desc->len - desc_offset, mbuf_avail); + if (copy_virtio_hdr) { + copy_virtio_hdr = 0; + virtio_enqueue_offload(mbuf, &(virtio_hdr->hdr)); + if (is_mrg_rxbuf) + virtio_hdr->num_buffers = extra_buffers + 1; + } + rte_memcpy((void *)(uintptr_t)desc_addr, rte_pktmbuf_mtod_offset(mbuf, void *, mbuf_len - mbuf_avail),