From owner-svn-src-head@freebsd.org Tue Jun 9 21:07:59 2020
Return-Path: <owner-svn-src-head@freebsd.org>
Delivered-To: svn-src-head@mailman.nyi.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1])
by mailman.nyi.freebsd.org (Postfix) with ESMTP id 1BB3B33CFA4;
Tue, 9 Jun 2020 21:07:59 +0000 (UTC)
(envelope-from rscheff@FreeBSD.org)
Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org
[IPv6:2610:1c1:1:606c::19:3])
(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)
key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256
client-signature RSA-PSS (4096 bits) client-digest SHA256)
(Client CN "mxrelay.nyi.freebsd.org",
Issuer "Let's Encrypt Authority X3" (verified OK))
by mx1.freebsd.org (Postfix) with ESMTPS id 49hN4Z74dhz3S3Z;
Tue, 9 Jun 2020 21:07:58 +0000 (UTC)
(envelope-from rscheff@FreeBSD.org)
Received: from repo.freebsd.org (repo.freebsd.org
[IPv6:2610:1c1:1:6068::e6a:0])
(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
(Client did not present a certificate)
by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id E92CB1BD64;
Tue, 9 Jun 2020 21:07:58 +0000 (UTC)
(envelope-from rscheff@FreeBSD.org)
Received: from repo.freebsd.org ([127.0.1.37])
by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id 059L7wog070121;
Tue, 9 Jun 2020 21:07:58 GMT (envelope-from rscheff@FreeBSD.org)
Received: (from rscheff@localhost)
by repo.freebsd.org (8.15.2/8.15.2/Submit) id 059L7wmK070120;
Tue, 9 Jun 2020 21:07:58 GMT (envelope-from rscheff@FreeBSD.org)
Message-Id: <202006092107.059L7wmK070120@repo.freebsd.org>
X-Authentication-Warning: repo.freebsd.org: rscheff set sender to
rscheff@FreeBSD.org using -f
From: Richard Scheffenegger <rscheff@FreeBSD.org>
Date: Tue, 9 Jun 2020 21:07:58 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
svn-src-head@freebsd.org
Subject: svn commit: r361987 - head/sys/netinet/cc
X-SVN-Group: head
X-SVN-Commit-Author: rscheff
X-SVN-Commit-Paths: head/sys/netinet/cc
X-SVN-Commit-Revision: 361987
X-SVN-Commit-Repository: base
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
X-BeenThere: svn-src-head@freebsd.org
X-Mailman-Version: 2.1.33
Precedence: list
List-Id: SVN commit messages for the src tree for head/-current
<svn-src-head.freebsd.org>
List-Unsubscribe: <https://lists.freebsd.org/mailman/options/svn-src-head>,
<mailto:svn-src-head-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/svn-src-head/>
List-Post: <mailto:svn-src-head@freebsd.org>
List-Help: <mailto:svn-src-head-request@freebsd.org?subject=help>
List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/svn-src-head>,
<mailto:svn-src-head-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 09 Jun 2020 21:07:59 -0000
Author: rscheff
Date: Tue Jun 9 21:07:58 2020
New Revision: 361987
URL: https://svnweb.freebsd.org/changeset/base/361987
Log:
Prevent TCP Cubic to abruptly increase cwnd after slow-start
Introducing flags to track the initial Wmax dragging and exit
from slow-start in TCP Cubic. This prevents sudden jumps in the
caluclated cwnd by cubic, especially when the flow is application
limited during slow start (cwnd can not grow as fast as expected).
The downside is that cubic may remain slightly longer in the
concave region before starting the convex region beyond Wmax again.
Reviewed by: chengc_netapp.com, tuexen (mentor)
Approved by: tuexen (mentor), rgrimes (mentor, blanket)
MFC after: 3 weeks
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D23655
Modified:
head/sys/netinet/cc/cc_cubic.c
Modified: head/sys/netinet/cc/cc_cubic.c
==============================================================================
--- head/sys/netinet/cc/cc_cubic.c Tue Jun 9 20:52:35 2020 (r361986)
+++ head/sys/netinet/cc/cc_cubic.c Tue Jun 9 21:07:58 2020 (r361987)
@@ -90,8 +90,10 @@ struct cubic {
unsigned long max_cwnd;
/* cwnd at the previous congestion event. */
unsigned long prev_max_cwnd;
- /* Number of congestion events. */
- uint32_t num_cong_events;
+ /* various flags */
+ uint32_t flags;
+#define CUBICFLAG_CONG_EVENT 0x00000001 /* congestion experienced */
+#define CUBICFLAG_IN_SLOWSTART 0x00000002 /* in slow start */
/* Minimum observed rtt in ticks. */
int min_rtt_ticks;
/* Mean observed rtt between congestion epochs. */
@@ -138,9 +140,10 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type)
(V_tcp_do_rfc3465 && ccv->flags & CCF_ABC_SENTAWND))) {
/* Use the logic in NewReno ack_received() for slow start. */
if (CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh) ||
- cubic_data->min_rtt_ticks == TCPTV_SRTTBASE)
+ cubic_data->min_rtt_ticks == TCPTV_SRTTBASE) {
+ cubic_data->flags |= CUBICFLAG_IN_SLOWSTART;
newreno_cc_algo.ack_received(ccv, type);
- else {
+ } else {
if ((ticks_since_cong =
ticks - cubic_data->t_last_cong) < 0) {
/*
@@ -150,6 +153,11 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type)
cubic_data->t_last_cong = ticks - INT_MAX;
}
+ if (cubic_data->flags & CUBICFLAG_IN_SLOWSTART) {
+ cubic_data->flags &= ~CUBICFLAG_IN_SLOWSTART;
+ cubic_data->t_last_cong = ticks;
+ cubic_data->K = 0;
+ }
/*
* The mean RTT is used to best reflect the equations in
* the I-D. Using min_rtt in the tf_cwnd calculation
@@ -199,7 +207,7 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type)
* keep updating our current estimate of the
* max_cwnd.
*/
- if (cubic_data->num_cong_events == 0 &&
+ if (((cubic_data->flags & CUBICFLAG_CONG_EVENT) == 0) &&
cubic_data->max_cwnd < CCV(ccv, snd_cwnd)) {
cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
cubic_data->K = cubic_k(cubic_data->max_cwnd /
@@ -270,9 +278,10 @@ cubic_cong_signal(struct cc_var *ccv, uint32_t type)
if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) {
if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
cubic_ssthresh_update(ccv);
- cubic_data->num_cong_events++;
+ cubic_data->flags |= CUBICFLAG_CONG_EVENT;
cubic_data->prev_max_cwnd = cubic_data->max_cwnd;
cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
+ cubic_data->K = cubic_k(cubic_data->max_cwnd / CCV(ccv, t_maxseg));
}
ENTER_RECOVERY(CCV(ccv, t_flags));
}
@@ -281,10 +290,11 @@ cubic_cong_signal(struct cc_var *ccv, uint32_t type)
case CC_ECN:
if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
cubic_ssthresh_update(ccv);
- cubic_data->num_cong_events++;
+ cubic_data->flags |= CUBICFLAG_CONG_EVENT;
cubic_data->prev_max_cwnd = cubic_data->max_cwnd;
cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
cubic_data->t_last_cong = ticks;
+ cubic_data->K = cubic_k(cubic_data->max_cwnd / CCV(ccv, t_maxseg));
CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
ENTER_CONGRECOVERY(CCV(ccv, t_flags));
}
@@ -299,7 +309,7 @@ cubic_cong_signal(struct cc_var *ccv, uint32_t type)
* congestion.
*/
if (CCV(ccv, t_rxtshift) >= 2) {
- cubic_data->num_cong_events++;
+ cubic_data->flags |= CUBICFLAG_CONG_EVENT;
cubic_data->t_last_cong = ticks;
}
break;
@@ -442,7 +452,7 @@ cubic_ssthresh_update(struct cc_var *ccv)
* On the first congestion event, set ssthresh to cwnd * 0.5, on
* subsequent congestion events, set it to cwnd * beta.
*/
- if (cubic_data->num_cong_events == 0)
+ if ((cubic_data->flags & CUBICFLAG_CONG_EVENT) == 0)
ssthresh = CCV(ccv, snd_cwnd) >> 1;
else
ssthresh = ((uint64_t)CCV(ccv, snd_cwnd) *