{"id":817374,"url":"http://patchwork.ozlabs.org/api/patches/817374/?format=json","web_url":"http://patchwork.ozlabs.org/project/netdev/patch/1506067355-5771-3-git-send-email-jasowang@redhat.com/","project":{"id":7,"url":"http://patchwork.ozlabs.org/api/projects/7/?format=json","name":"Linux network development","link_name":"netdev","list_id":"netdev.vger.kernel.org","list_email":"netdev@vger.kernel.org","web_url":null,"scm_url":null,"webscm_url":null,"list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<1506067355-5771-3-git-send-email-jasowang@redhat.com>","list_archive_url":null,"date":"2017-09-22T08:02:32","name":"[net-next,RFC,2/5] vhost: introduce helper to prefetch desc index","commit_ref":null,"pull_url":null,"state":"rfc","archived":true,"hash":"6b8de41dd2c78474e5902f60d8c18a51894b9d16","submitter":{"id":5225,"url":"http://patchwork.ozlabs.org/api/people/5225/?format=json","name":"Jason Wang","email":"jasowang@redhat.com"},"delegate":{"id":34,"url":"http://patchwork.ozlabs.org/api/users/34/?format=json","username":"davem","first_name":"David","last_name":"Miller","email":"davem@davemloft.net"},"mbox":"http://patchwork.ozlabs.org/project/netdev/patch/1506067355-5771-3-git-send-email-jasowang@redhat.com/mbox/","series":[{"id":4565,"url":"http://patchwork.ozlabs.org/api/series/4565/?format=json","web_url":"http://patchwork.ozlabs.org/project/netdev/list/?series=4565","date":"2017-09-22T08:02:35","name":"batched tx processing in vhost_net","version":1,"mbox":"http://patchwork.ozlabs.org/series/4565/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/817374/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/817374/checks/","tags":{},"related":[],"headers":{"Return-Path":"","X-Original-To":"patchwork-incoming@ozlabs.org","Delivered-To":"patchwork-incoming@ozlabs.org","Authentication-Results":["ozlabs.org;\n\tspf=none (mailfrom) smtp.mailfrom=vger.kernel.org\n\t(client-ip=209.132.180.67; helo=vger.kernel.org;\n\tenvelope-from=netdev-owner@vger.kernel.org;\n\treceiver=)","ext-mx08.extmail.prod.ext.phx2.redhat.com;\n\tdmarc=none (p=none dis=none) header.from=redhat.com","ext-mx08.extmail.prod.ext.phx2.redhat.com;\n\tspf=fail smtp.mailfrom=jasowang@redhat.com"],"Received":["from vger.kernel.org (vger.kernel.org [209.132.180.67])\n\tby ozlabs.org (Postfix) with ESMTP id 3xz5bB6KJlz9sNc\n\tfor ;\n\tFri, 22 Sep 2017 18:03:50 +1000 (AEST)","(majordomo@vger.kernel.org) by vger.kernel.org via listexpand\n\tid S1752013AbdIVIC4 (ORCPT );\n\tFri, 22 Sep 2017 04:02:56 -0400","from mx1.redhat.com ([209.132.183.28]:55846 \"EHLO mx1.redhat.com\"\n\trhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP\n\tid S1751995AbdIVICv (ORCPT );\n\tFri, 22 Sep 2017 04:02:51 -0400","from smtp.corp.redhat.com\n\t(int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15])\n\t(using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))\n\t(No client certificate requested)\n\tby mx1.redhat.com (Postfix) with ESMTPS id 2DBA3C0546D1;\n\tFri, 22 Sep 2017 08:02:51 +0000 (UTC)","from jason-ThinkPad-T450s.redhat.com (ovpn-12-19.pek2.redhat.com\n\t[10.72.12.19])\n\tby smtp.corp.redhat.com (Postfix) with ESMTP id D7AA962679;\n\tFri, 22 Sep 2017 08:02:47 +0000 (UTC)"],"DMARC-Filter":"OpenDMARC Filter v1.3.2 mx1.redhat.com 2DBA3C0546D1","From":"Jason Wang ","To":"mst@redhat.com, jasowang@redhat.com,\n\tvirtualization@lists.linux-foundation.org, netdev@vger.kernel.org,\n\tlinux-kernel@vger.kernel.org","Cc":"kvm@vger.kernel.org","Subject":"[PATCH net-next RFC 2/5] vhost: introduce helper to prefetch desc\n\tindex","Date":"Fri, 22 Sep 2017 16:02:32 +0800","Message-Id":"<1506067355-5771-3-git-send-email-jasowang@redhat.com>","In-Reply-To":"<1506067355-5771-1-git-send-email-jasowang@redhat.com>","References":"<1506067355-5771-1-git-send-email-jasowang@redhat.com>","X-Scanned-By":"MIMEDefang 2.79 on 10.5.11.15","X-Greylist":"Sender IP whitelisted, not delayed by milter-greylist-4.5.16\n\t(mx1.redhat.com [10.5.110.32]);\n\tFri, 22 Sep 2017 08:02:51 +0000 (UTC)","Sender":"netdev-owner@vger.kernel.org","Precedence":"bulk","List-ID":"","X-Mailing-List":"netdev@vger.kernel.org"},"content":"This patch introduces vhost_prefetch_desc_indices() which could batch\ndescriptor indices fetching and used ring updating. This intends to\nreduce the cache misses of indices fetching and updating and reduce\ncache line bounce when virtqueue is almost full. copy_to_user() was\nused in order to benefit from modern cpus that support fast string\ncopy. Batched virtqueue processing will be the first user.\n\nSigned-off-by: Jason Wang \n---\n drivers/vhost/vhost.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++\n drivers/vhost/vhost.h | 3 +++\n 2 files changed, 58 insertions(+)","diff":"diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c\nindex f87ec75..8424166d 100644\n--- a/drivers/vhost/vhost.c\n+++ b/drivers/vhost/vhost.c\n@@ -2437,6 +2437,61 @@ struct vhost_msg_node *vhost_dequeue_msg(struct vhost_dev *dev,\n }\n EXPORT_SYMBOL_GPL(vhost_dequeue_msg);\n \n+int vhost_prefetch_desc_indices(struct vhost_virtqueue *vq,\n+\t\t\t\tstruct vring_used_elem *heads,\n+\t\t\t\tu16 num, bool used_update)\n+{\n+\tint ret, ret2;\n+\tu16 last_avail_idx, last_used_idx, total, copied;\n+\t__virtio16 avail_idx;\n+\tstruct vring_used_elem __user *used;\n+\tint i;\n+\n+\tif (unlikely(vhost_get_avail(vq, avail_idx, &vq->avail->idx))) {\n+\t\tvq_err(vq, \"Failed to access avail idx at %p\\n\",\n+\t\t &vq->avail->idx);\n+\t\treturn -EFAULT;\n+\t}\n+\tlast_avail_idx = vq->last_avail_idx & (vq->num - 1);\n+\tvq->avail_idx = vhost16_to_cpu(vq, avail_idx);\n+\ttotal = vq->avail_idx - vq->last_avail_idx;\n+\tret = total = min(total, num);\n+\n+\tfor (i = 0; i < ret; i++) {\n+\t\tret2 = vhost_get_avail(vq, heads[i].id,\n+\t\t\t\t &vq->avail->ring[last_avail_idx]);\n+\t\tif (unlikely(ret2)) {\n+\t\t\tvq_err(vq, \"Failed to get descriptors\\n\");\n+\t\t\treturn -EFAULT;\n+\t\t}\n+\t\tlast_avail_idx = (last_avail_idx + 1) & (vq->num - 1);\n+\t}\n+\n+\tif (!used_update)\n+\t\treturn ret;\n+\n+\tlast_used_idx = vq->last_used_idx & (vq->num - 1);\n+\twhile (total) {\n+\t\tcopied = min((u16)(vq->num - last_used_idx), total);\n+\t\tret2 = vhost_copy_to_user(vq,\n+\t\t\t\t\t &vq->used->ring[last_used_idx],\n+\t\t\t\t\t &heads[ret - total],\n+\t\t\t\t\t copied * sizeof(*used));\n+\n+\t\tif (unlikely(ret2)) {\n+\t\t\tvq_err(vq, \"Failed to update used ring!\\n\");\n+\t\t\treturn -EFAULT;\n+\t\t}\n+\n+\t\tlast_used_idx = 0;\n+\t\ttotal -= copied;\n+\t}\n+\n+\t/* Only get avail ring entries after they have been exposed by guest. */\n+\tsmp_rmb();\n+\treturn ret;\n+}\n+EXPORT_SYMBOL(vhost_prefetch_desc_indices);\n \n static int __init vhost_init(void)\n {\ndiff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h\nindex 39ff897..16c2cb6 100644\n--- a/drivers/vhost/vhost.h\n+++ b/drivers/vhost/vhost.h\n@@ -228,6 +228,9 @@ ssize_t vhost_chr_read_iter(struct vhost_dev *dev, struct iov_iter *to,\n ssize_t vhost_chr_write_iter(struct vhost_dev *dev,\n \t\t\t struct iov_iter *from);\n int vhost_init_device_iotlb(struct vhost_dev *d, bool enabled);\n+int vhost_prefetch_desc_indices(struct vhost_virtqueue *vq,\n+\t\t\t\tstruct vring_used_elem *heads,\n+\t\t\t\tu16 num, bool used_update);\n \n #define vq_err(vq, fmt, ...) do { \\\n \t\tpr_debug(pr_fmt(fmt), ##__VA_ARGS__); \\\n","prefixes":["net-next","RFC","2/5"]}