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=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 8439DC10F11 for ; Wed, 10 Apr 2019 12:02:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3C7A120818 for ; Wed, 10 Apr 2019 12:02:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="QUFqBIUz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731641AbfDJMCC (ORCPT ); Wed, 10 Apr 2019 08:02:02 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:53128 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727515AbfDJMCC (ORCPT ); Wed, 10 Apr 2019 08:02:02 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Mime-Version:Content-Type:Date:To: From:Subject:Message-ID:Sender:Reply-To:Cc:Content-Transfer-Encoding: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=EDQw+5DVLQbDf/hon4gXGp2vq9Fbjz+x8IdrzDLCpvw=; b=QUFqBIUzlZxZvQto00XAAFm2e DxV8SLOCjBvWe4XiT8ep16IEjU8OS4z0jESEckcEEN+IewOCXdDfkGsyOxz7ySgdwHybbyQOzueHo MtjHBUNnJi09ZsWX5M3DmP2Juze8iDB7L9PuxIDG8w0jCkWM8XGjZlJpuOR24KFkWPDN4EBjpH30U 5rctZ1dQZk+OvTDqc35oNLBx/TimgIW9KqXRp9VqcRqTGFzUmCcKqPelU4NdnrXAoBzrGOxM2YFHP e+E4gBHA2oxNIPxuUdXTiIUaMpIXhJJhqAKvHt8UaIpRAyBQokM7GkSxqEAH1/drMf/so8JK7ekrK VRKFIp4aQ==; Received: from 54-240-197-235.amazon.com ([54.240.197.235] helo=u3832b3a9db3152.ant.amazon.com) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hEBvV-0003q5-7G for netdev@vger.kernel.org; Wed, 10 Apr 2019 12:02:01 +0000 Message-ID: <2e310fc6ee847d20dd23692fd1db733e607602f5.camel@infradead.org> Subject: Tun congestion/BQL From: David Woodhouse To: netdev@vger.kernel.org Date: Wed, 10 Apr 2019 15:01:58 +0300 Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-GWY+jgV9YXJWB3ltRfMB" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.1 Mime-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org --=-GWY+jgV9YXJWB3ltRfMB Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable I've been working on OpenConnect VPN performance. After fixing some local stupidities I am basically crypto-bound as I suck packets out of the tun device and feed them out over the public network as fast as the crypto library can encrypt them. However, the tun device is dropping packets. I'm testing with an ESP setup that the kernel happens to support. If I do netperf UDP_STREAM testing with the kernel doing ESP, I get this: Socket Message Elapsed Messages =20 Size Size Time Okay Errors Throughput bytes bytes secs # # 10^6bits/sec 212992 1400 10.00 1198093 0 1341.86 212992 10.00 1198044 1341.80 Change to doing it in userspace through the tun device, though, and it looks more like this: Socket Message Elapsed Messages =20 Size Size Time Okay Errors Throughput bytes bytes secs # # 10^6bits/sec 212992 1400 10.00 8194693 0 9178.04 212992 10.00 1536155 1720.49 The discrepancy between sent and received packets is all seen as packet loss on the tun0 interface, where userspace is not reading the packets out fast enough: $ netstat -i Kernel Interface table Iface MTU RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP = TX-OVR Flg eth0 9001 56790193 0 1718127 0 129849068 0 = 0 0 BMRU lo 65536 42 0 0 0 42 0 0 = 0 LRU tun0 1500 9 0 0 0 1546968 0 6647739= 0 MOPRU So... I threw together something to stop the queue when the tx_ring was full (which I know is incomplete but was enough for my test) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index e9ca1c088d0b..a15fca23ef45 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1125,7 +1128,9 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, = struct net_device *dev) if (tfile->flags & TUN_FASYNC) kill_fasync(&tfile->fasync, SIGIO, POLL_IN); tfile->socket.sk->sk_data_ready(tfile->socket.sk); =20 + if (!ptr_ring_empty(&tfile->tx_ring)) + netif_stop_queue(tun->dev); rcu_read_unlock(); return NETDEV_TX_OK; =20 @@ -2237,7 +2239,7 @@ static ssize_t tun_do_read(struct tun_struct *tun, st= ruct tun_file *tfile, else consume_skb(skb); } - + netif_wake_queue(tun->dev); return ret; } =20 So now netperf doesn't send lots of packets that get dropped by the tun device. But it doesn't send anywhere near as many packets successfully, either... Socket Message Elapsed Messages =20 Size Size Time Okay Errors Throughput bytes bytes secs # # 10^6bits/sec 212992 1400 10.00 1250223 0 1400.25 212992 10.00 1245458 1394.91 That's actually dropped me back to the performance I was getting with the kernel's ESP implementation. Is that something we should expect? I don't think it's purely the overhead I've added in the driver. If I leave the netif_wake_queue() and add '&& 0' to the condition for the netif_stop_queue(), which should still leave the locking in the ptr_ring_empty() to happen, the performance goes back up. What's going on? Am I actually better off letting it drop packets silently? --=-GWY+jgV9YXJWB3ltRfMB Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCECow ggUcMIIEBKADAgECAhEA4rtJSHkq7AnpxKUY8ZlYZjANBgkqhkiG9w0BAQsFADCBlzELMAkGA1UE BhMCR0IxGzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UEBxMHU2FsZm9yZDEaMBgG A1UEChMRQ09NT0RPIENBIExpbWl0ZWQxPTA7BgNVBAMTNENPTU9ETyBSU0EgQ2xpZW50IEF1dGhl bnRpY2F0aW9uIGFuZCBTZWN1cmUgRW1haWwgQ0EwHhcNMTkwMTAyMDAwMDAwWhcNMjIwMTAxMjM1 OTU5WjAkMSIwIAYJKoZIhvcNAQkBFhNkd213MkBpbmZyYWRlYWQub3JnMIIBIjANBgkqhkiG9w0B AQEFAAOCAQ8AMIIBCgKCAQEAsv3wObLTCbUA7GJqKj9vHGf+Fa+tpkO+ZRVve9EpNsMsfXhvFpb8 RgL8vD+L133wK6csYoDU7zKiAo92FMUWaY1Hy6HqvVr9oevfTV3xhB5rQO1RHJoAfkvhy+wpjo7Q cXuzkOpibq2YurVStHAiGqAOMGMXhcVGqPuGhcVcVzVUjsvEzAV9Po9K2rpZ52FE4rDkpDK1pBK+ 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