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[52.52.7.82]) by smtp.gmail.com with ESMTPSA id y12-20020a05620a25cc00b006bb78d095c5sm9862563qko.79.2022.08.22.02.12.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Aug 2022 02:12:41 -0700 (PDT) From: Peilin Ye To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Jonathan Corbet , Hideaki YOSHIFUJI , David Ahern , Jamal Hadi Salim , Cong Wang , Jiri Pirko Cc: Peilin Ye , netdev@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Cong Wang , Stephen Hemminger , Dave Taht , Peilin Ye Subject: [PATCH RFC v2 net-next 3/5] net/sched: sch_tbf: Use Qdisc backpressure infrastructure Date: Mon, 22 Aug 2022 02:12:34 -0700 Message-Id: X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peilin Ye Recently we introduced a Qdisc backpressure infrastructure (currently supports UDP sockets). Use it in TBF Qdisc. Tested with 500 Mbits/sec rate limit and SFQ inner Qdisc using 16 iperf UDP 1 Gbit/sec clients. Before: [ 3] 0.0-15.0 sec 53.6 MBytes 30.0 Mbits/sec 0.208 ms 1190234/1228450 (97%) [ 3] 0.0-15.0 sec 54.7 MBytes 30.6 Mbits/sec 0.085 ms 955591/994593 (96%) [ 3] 0.0-15.0 sec 55.4 MBytes 31.0 Mbits/sec 0.170 ms 966364/1005868 (96%) [ 3] 0.0-15.0 sec 55.0 MBytes 30.8 Mbits/sec 0.167 ms 925083/964333 (96%) <...> ^^^^^^^^^^^^^^^^^^^ Total throughput is 480.2 Mbits/sec and average drop rate is 96.5%. Now enable Qdisc backpressure for UDP sockets, with udp_backpressure_interval default to 100 milliseconds: [ 3] 0.0-15.0 sec 54.4 MBytes 30.4 Mbits/sec 0.097 ms 450/39246 (1.1%) [ 3] 0.0-15.0 sec 54.4 MBytes 30.4 Mbits/sec 0.331 ms 435/39232 (1.1%) [ 3] 0.0-15.0 sec 54.4 MBytes 30.4 Mbits/sec 0.040 ms 435/39212 (1.1%) [ 3] 0.0-15.0 sec 54.4 MBytes 30.4 Mbits/sec 0.031 ms 426/39208 (1.1%) <...> ^^^^^^^^^^^^^^^^ Total throughput is 486.4 Mbits/sec (1.29% higher) and average drop rate is 1.1% (98.86% lower). However, enabling Qdisc backpressure affects fairness between flow if we use TBF Qdisc with default bfifo inner Qdisc: [ 3] 0.0-15.0 sec 46.1 MBytes 25.8 Mbits/sec 1.102 ms 142/33048 (0.43%) [ 3] 0.0-15.0 sec 72.8 MBytes 40.7 Mbits/sec 0.476 ms 145/52081 (0.28%) [ 3] 0.0-15.0 sec 53.2 MBytes 29.7 Mbits/sec 1.047 ms 141/38086 (0.37%) [ 3] 0.0-15.0 sec 45.5 MBytes 25.4 Mbits/sec 1.600 ms 141/32573 (0.43%) <...> ^^^^^^^^^^^^^^^^^ In the test, per-flow throughput ranged from 16.4 to 68.7 Mbits/sec. However, total throughput was still 486.4 Mbits/sec (0.87% higher than before), and average drop rate was 0.41% (99.58% lower than before). Signed-off-by: Peilin Ye --- net/sched/sch_tbf.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c index 72102277449e..cf9cc7dbf078 100644 --- a/net/sched/sch_tbf.c +++ b/net/sched/sch_tbf.c @@ -222,6 +222,7 @@ static int tbf_segment(struct sk_buff *skb, struct Qdisc *sch, len += segs->len; ret = qdisc_enqueue(segs, q->qdisc, to_free); if (ret != NET_XMIT_SUCCESS) { + qdisc_backpressure(skb); if (net_xmit_drop_count(ret)) qdisc_qstats_drop(sch); } else { @@ -250,6 +251,7 @@ static int tbf_enqueue(struct sk_buff *skb, struct Qdisc *sch, } ret = qdisc_enqueue(skb, q->qdisc, to_free); if (ret != NET_XMIT_SUCCESS) { + qdisc_backpressure(skb); if (net_xmit_drop_count(ret)) qdisc_qstats_drop(sch); return ret; -- 2.20.1