Date: Fri, 1 Apr 2022 12:35:38 GMT From: Randall Stewart <rrs@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 653cf466f085 - main - hystart++ may not properly exit CSS back to slowstart. Message-ID: <202204011235.231CZcVL060594@gitrepo.freebsd.org>
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The branch main has been updated by rrs: URL: https://cgit.FreeBSD.org/src/commit/?id=653cf466f08584c0fd87bc336cdc1db08f0d4434 commit 653cf466f08584c0fd87bc336cdc1db08f0d4434 Author: Randall Stewart <rrs@FreeBSD.org> AuthorDate: 2022-04-01 12:33:44 +0000 Commit: Randall Stewart <rrs@FreeBSD.org> CommitDate: 2022-04-01 12:33:44 +0000 hystart++ may not properly exit CSS back to slowstart. In the changes to get hystart++ into cubic an inadvertent line was removed in the conditional to figure out if you need to exit hystart++ back to slowstart. The line of course is the most crucial one (the others are valid but not critical) i.e. is the new rtt less than the point where we entered hystart++. Without the line we end up bouncing in and out of CSS. Reported By: Reese Enghardt Sponsored By: Netflix Inc. --- sys/netinet/cc/cc_cubic.c | 1 + sys/netinet/cc/cc_newreno.c | 1 + 2 files changed, 2 insertions(+) diff --git a/sys/netinet/cc/cc_cubic.c b/sys/netinet/cc/cc_cubic.c index e7d86a25156a..0291776928d4 100644 --- a/sys/netinet/cc/cc_cubic.c +++ b/sys/netinet/cc/cc_cubic.c @@ -658,6 +658,7 @@ cubic_rttsample(struct cc_var *ccv, uint32_t usec_rtt, uint32_t rxtcnt, uint32_t } if ((cubicd->css_rttsample_count >= hystart_n_rttsamples) && (cubicd->css_current_round_minrtt != 0xffffffff) && + (cubicd->css_current_round_minrtt < nreno->css_baseline_minrtt) && (cubicd->css_lastround_minrtt != 0xffffffff)) { /* * We were in CSS and the RTT is now less, we diff --git a/sys/netinet/cc/cc_newreno.c b/sys/netinet/cc/cc_newreno.c index 06b53d76d8e9..90895e0f6988 100644 --- a/sys/netinet/cc/cc_newreno.c +++ b/sys/netinet/cc/cc_newreno.c @@ -571,6 +571,7 @@ newreno_rttsample(struct cc_var *ccv, uint32_t usec_rtt, uint32_t rxtcnt, uint32 } if ((nreno->css_rttsample_count >= hystart_n_rttsamples) && (nreno->css_current_round_minrtt != 0xffffffff) && + (nreno->css_current_round_minrtt < nreno->css_baseline_minrtt) && (nreno->css_lastround_minrtt != 0xffffffff)) { /* * We were in CSS and the RTT is now less, we
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