From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E04F4C433FF for ; Sat, 10 Aug 2019 20:48:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B56DE208C3 for ; Sat, 10 Aug 2019 20:48:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726992AbfHJUsU (ORCPT ); Sat, 10 Aug 2019 16:48:20 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:54850 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726800AbfHJUoB (ORCPT ); Sat, 10 Aug 2019 16:44:01 -0400 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hwYDV-00053W-KH; Sat, 10 Aug 2019 21:43:57 +0100 Received: from ben by deadeye with local (Exim 4.92) (envelope-from ) id 1hwYDO-0003j2-3v; Sat, 10 Aug 2019 21:43:50 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Yunfang Tai" , "David S. Miller" , "Lidong Chen" , "Michael S. Tsirkin" , "=?UTF-8?q?haibinzhang=28=E5=BC=A0=E6=B5=B7=E6=96=8C=29?=" Date: Sat, 10 Aug 2019 21:40:07 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 129/157] vhost-net: set packet weight of tx polling to 2 * vq size In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 3.16.72-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: haibinzhang(张海斌) commit a2ac99905f1ea8b15997a6ec39af69aa28a3653b upstream. handle_tx will delay rx for tens or even hundreds of milliseconds when tx busy polling udp packets with small length(e.g. 1byte udp payload), because setting VHOST_NET_WEIGHT takes into account only sent-bytes but no single packet length. Ping-Latencies shown below were tested between two Virtual Machines using netperf (UDP_STREAM, len=1), and then another machine pinged the client: vq size=256 Packet-Weight Ping-Latencies(millisecond) min avg max Origin 3.319 18.489 57.303 64 1.643 2.021 2.552 128 1.825 2.600 3.224 256 1.997 2.710 4.295 512 1.860 3.171 4.631 1024 2.002 4.173 9.056 2048 2.257 5.650 9.688 4096 2.093 8.508 15.943 vq size=512 Packet-Weight Ping-Latencies(millisecond) min avg max Origin 6.537 29.177 66.245 64 2.798 3.614 4.403 128 2.861 3.820 4.775 256 3.008 4.018 4.807 512 3.254 4.523 5.824 1024 3.079 5.335 7.747 2048 3.944 8.201 12.762 4096 4.158 11.057 19.985 Seems pretty consistent, a small dip at 2 VQ sizes. Ring size is a hint from device about a burst size it can tolerate. Based on benchmarks, set the weight to 2 * vq size. To evaluate this change, another tests were done using netperf(RR, TX) between two machines with Intel(R) Xeon(R) Gold 6133 CPU @ 2.50GHz, and vq size was tweaked through qemu. Results shown below does not show obvious changes. vq size=256 TCP_RR vq size=512 TCP_RR size/sessions/+thu%/+normalize% size/sessions/+thu%/+normalize% 1/ 1/ -7%/ -2% 1/ 1/ 0%/ -2% 1/ 4/ +1%/ 0% 1/ 4/ +1%/ 0% 1/ 8/ +1%/ -2% 1/ 8/ 0%/ +1% 64/ 1/ -6%/ 0% 64/ 1/ +7%/ +3% 64/ 4/ 0%/ +2% 64/ 4/ -1%/ +1% 64/ 8/ 0%/ 0% 64/ 8/ -1%/ -2% 256/ 1/ -3%/ -4% 256/ 1/ -4%/ -2% 256/ 4/ +3%/ +4% 256/ 4/ +1%/ +2% 256/ 8/ +2%/ 0% 256/ 8/ +1%/ -1% vq size=256 UDP_RR vq size=512 UDP_RR size/sessions/+thu%/+normalize% size/sessions/+thu%/+normalize% 1/ 1/ -5%/ +1% 1/ 1/ -3%/ -2% 1/ 4/ +4%/ +1% 1/ 4/ -2%/ +2% 1/ 8/ -1%/ -1% 1/ 8/ -1%/ 0% 64/ 1/ -2%/ -3% 64/ 1/ +1%/ +1% 64/ 4/ -5%/ -1% 64/ 4/ +2%/ 0% 64/ 8/ 0%/ -1% 64/ 8/ -2%/ +1% 256/ 1/ +7%/ +1% 256/ 1/ -7%/ 0% 256/ 4/ +1%/ +1% 256/ 4/ -3%/ -4% 256/ 8/ +2%/ +2% 256/ 8/ +1%/ +1% vq size=256 TCP_STREAM vq size=512 TCP_STREAM size/sessions/+thu%/+normalize% size/sessions/+thu%/+normalize% 64/ 1/ 0%/ -3% 64/ 1/ 0%/ 0% 64/ 4/ +3%/ -1% 64/ 4/ -2%/ +4% 64/ 8/ +9%/ -4% 64/ 8/ -1%/ +2% 256/ 1/ +1%/ -4% 256/ 1/ +1%/ +1% 256/ 4/ -1%/ -1% 256/ 4/ -3%/ 0% 256/ 8/ +7%/ +5% 256/ 8/ -3%/ 0% 512/ 1/ +1%/ 0% 512/ 1/ -1%/ -1% 512/ 4/ +1%/ -1% 512/ 4/ 0%/ 0% 512/ 8/ +7%/ -5% 512/ 8/ +6%/ -1% 1024/ 1/ 0%/ -1% 1024/ 1/ 0%/ +1% 1024/ 4/ +3%/ 0% 1024/ 4/ +1%/ 0% 1024/ 8/ +8%/ +5% 1024/ 8/ -1%/ 0% 2048/ 1/ +2%/ +2% 2048/ 1/ -1%/ 0% 2048/ 4/ +1%/ 0% 2048/ 4/ 0%/ -1% 2048/ 8/ -2%/ 0% 2048/ 8/ 5%/ -1% 4096/ 1/ -2%/ 0% 4096/ 1/ -2%/ 0% 4096/ 4/ +2%/ 0% 4096/ 4/ 0%/ 0% 4096/ 8/ +9%/ -2% 4096/ 8/ -5%/ -1% Acked-by: Michael S. Tsirkin Signed-off-by: Haibin Zhang Signed-off-by: Yunfang Tai Signed-off-by: Lidong Chen Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- drivers/vhost/net.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -39,6 +39,10 @@ MODULE_PARM_DESC(experimental_zcopytx, " * Using this limit prevents one virtqueue from starving others. */ #define VHOST_NET_WEIGHT 0x80000 +/* Max number of packets transferred before requeueing the job. + * Using this limit prevents one virtqueue from starving rx. */ +#define VHOST_NET_PKT_WEIGHT(vq) ((vq)->num * 2) + /* MAX number of TX used buffers for outstanding zerocopy */ #define VHOST_MAX_PEND 128 #define VHOST_GOODCOPY_LEN 256 @@ -351,6 +355,7 @@ static void handle_tx(struct vhost_net * struct socket *sock; struct vhost_net_ubuf_ref *uninitialized_var(ubufs); bool zcopy, zcopy_used; + int sent_pkts = 0; mutex_lock(&vq->mutex); sock = vq->private_data; @@ -450,7 +455,8 @@ static void handle_tx(struct vhost_net * vhost_zerocopy_signal_used(net, vq); total_len += len; vhost_net_tx_packet(net); - if (unlikely(total_len >= VHOST_NET_WEIGHT)) { + if (unlikely(total_len >= VHOST_NET_WEIGHT) || + unlikely(++sent_pkts >= VHOST_NET_PKT_WEIGHT(vq))) { vhost_poll_queue(&vq->poll); break; }