{"id":687,"date":"2021-12-06T23:22:28","date_gmt":"2021-12-06T15:22:28","guid":{"rendered":"https:\/\/blog.cauchyschwarz.com\/?p=687"},"modified":"2021-12-06T23:48:35","modified_gmt":"2021-12-06T15:48:35","slug":"linux%e5%86%85%e6%a0%b8bbr%e4%bb%a3%e7%a0%81%e7%ac%94%e8%ae%b0","status":"publish","type":"post","link":"https:\/\/blog.cauchyschwarz.com\/?p=687","title":{"rendered":"Linux\u5185\u6838BBR\u4ee3\u7801\u7b14\u8bb0"},"content":{"rendered":"\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_82_2 ez-toc-wrap-right counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<label for=\"ez-toc-cssicon-toggle-item-69e10325c9c1a\" class=\"ez-toc-cssicon-toggle-label\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/label><input type=\"checkbox\"  id=\"ez-toc-cssicon-toggle-item-69e10325c9c1a\" checked aria-label=\"Toggle\" \/><nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-1'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#%E6%BA%90%E7%A0%81\" >\u6e90\u7801<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-1'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#%E6%A0%B8%E5%BF%83%E7%AE%97%E6%B3%95\" >\u6838\u5fc3\u7b97\u6cd5<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-1'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#%E5%85%A8%E5%B1%80%E5%8F%82%E6%95%B0\" >\u5168\u5c40\u53c2\u6570<\/a><ul class='ez-toc-list-level-2' ><li class='ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#%E5%B8%A6%E5%AE%BD%E8%AE%A1%E7%AE%97\" >\u5e26\u5bbd\u8ba1\u7b97<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#%E5%AE%9A%E7%82%B9%E5%8C%96\" >\u5b9a\u70b9\u5316<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-1'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#%E5%85%A8%E5%B1%80%E5%8F%98%E9%87%8F\" >\u5168\u5c40\u53d8\u91cf<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-1'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#%E9%87%8D%E8%A6%81%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84\" >\u91cd\u8981\u6570\u636e\u7ed3\u6784<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-1'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#%E9%87%8D%E8%A6%81%E5%87%BD%E6%95%B0\" >\u91cd\u8981\u51fd\u6570<\/a><ul class='ez-toc-list-level-2' ><li class='ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_init\" >bbr_init<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_main\" >bbr_main<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_sndbuf_expand\" >bbr_sndbuf_expand<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_undo_cwnd\" >bbr_undo_cwnd<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_ssthresh\" >bbr_ssthresh<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_min_tso_segs\" >bbr_min_tso_segs<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_get_info\" >bbr_get_info<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-16\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_set_state\" >bbr_set_state<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-1'><a class=\"ez-toc-link ez-toc-heading-17\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#%E5%86%85%E9%83%A8%E5%87%BD%E6%95%B0\" >\u5185\u90e8\u51fd\u6570<\/a><ul class='ez-toc-list-level-2' ><li class='ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-18\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_save_cwnd\" >bbr_save_cwnd<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-19\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_update_model\" >bbr_update_model<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-20\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_update_bw\" >bbr_update_bw<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-21\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_update_ack_aggregation\" >bbr_update_ack_aggregation<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-22\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_update_cycle_phase\" >bbr_update_cycle_phase<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-23\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_check_full_bw_reached\" >bbr_check_full_bw_reached<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-24\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_check_drain\" >bbr_check_drain<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-25\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_update_min_rtt\" >bbr_update_min_rtt<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-26\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=687\/#bbr_update_gains\" >bbr_update_gains<\/a><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E6%BA%90%E7%A0%81\"><\/span><a href=\"https:\/\/elixir.bootlin.com\/linux\/v5.16-rc3\/source\/net\/ipv4\/tcp_bbr.c\">\u6e90\u7801<\/a><span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<p>\u7248\u672c5.16-rc3<\/p>\n\n\n\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E6%A0%B8%E5%BF%83%E7%AE%97%E6%B3%95\"><\/span>\u6838\u5fc3\u7b97\u6cd5<span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<p>&nbsp;&nbsp;&nbsp;On each ACK, update our model of the network path:<\/p>\n\n\n\n<p><strong>&nbsp;&nbsp;&nbsp;bottleneck_bandwidth = windowed_max(delivered \/ elapsed, 10 round trips)<\/strong><\/p>\n\n\n\n<p><strong>&nbsp;&nbsp;&nbsp;min_rtt = windowed_min(rtt, 10 seconds)<\/strong><\/p>\n\n\n\n<p><strong>&nbsp;&nbsp;&nbsp;pacing_rate = pacing_gain * bottleneck_bandwidth<\/strong><\/p>\n\n\n\n<p><strong>\u00a0\u00a0\u00a0cwnd = max(cwnd_gain * bottleneck_bandwidth * min_rtt, 4)<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\"> * Here is a state transition diagram for BBR:\n *\n *             |\n *             V\n *    +---> STARTUP  ----+\n *    |        |         |\n *    |        V         |\n *    |      DRAIN   ----+\n *    |        |         |\n *    |        V         |\n *    +---> PROBE_BW ----+\n *    |      ^    |      |\n *    |      |    |      |\n *    |      +----+      |\n *    |                  |\n *    +---- PROBE_RTT &lt;--+\n<\/code><\/pre>\n\n\n\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%85%A8%E5%B1%80%E5%8F%82%E6%95%B0\"><\/span>\u5168\u5c40\u53c2\u6570<span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%B8%A6%E5%AE%BD%E8%AE%A1%E7%AE%97\"><\/span>\u5e26\u5bbd\u8ba1\u7b97<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\">#define BW_SCALE 24\n#define BW_UNIT (1 &lt;&lt; BW_SCALE)<\/code><\/pre>\n\n\n\n<p>\u7528\u4e00\u4e2au32(\u4f4eBW_SCALE\u90e8\u5206\u4e3a\u5c0f\u6570\u90e8\u5206)\u6765\u8868\u793a\u6bcf1us\u53d1\u9001\u7684\u5305\u6570\uff0c\u6309\u7167\u6bcf\u4e2a\u5305\u5927\u5c0f1500byte\u7b97\uff0c\u8fd9\u4e2au32\u53ef\u4ee5\u8868\u793a\u7684\u5e26\u5bbd\u8303\u56f4\u4e3a0.06pps(715bps)\u5230256Mpps(3Tbps)\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%AE%9A%E7%82%B9%E5%8C%96\"><\/span>\u5b9a\u70b9\u5316<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\">#define BBR_SCALE 8\t\/* scaling factor for fractions in BBR (e.g. gains) *\/\n#define BBR_UNIT (1 &lt;&lt; BBR_SCALE)<\/code><\/pre>\n\n\n\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%85%A8%E5%B1%80%E5%8F%98%E9%87%8F\"><\/span>\u5168\u5c40\u53d8\u91cf<span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\">\/* Window length of bw filter (in rounds): *\/\nstatic const int bbr_bw_rtts = CYCLE_LEN + 2;\n\/* Window length of min_rtt filter (in sec): *\/\nstatic const u32 bbr_min_rtt_win_sec = 10;\n\/* Minimum time (in ms) spent at bbr_cwnd_min_target in BBR_PROBE_RTT mode: *\/\nstatic const u32 bbr_probe_rtt_mode_ms = 200;\n\/* Skip TSO below the following bandwidth (bits\/sec): *\/\nstatic const int bbr_min_tso_rate = 1200000; \/\/ \u5c0f\u4e8e1.2Mbps\u5c31\u522b\u7528tso\u4e86\nstatic const int bbr_pacing_margin_percent = 1; \/\/ \u4e0d\u8981\u7528\u6ee1\u5e26\u5bbd\uff0c\u75591%\nstatic const int bbr_high_gain  = BBR_UNIT * 2885 \/ 1000 + 1;\nstatic const int bbr_drain_gain = BBR_UNIT * 1000 \/ 2885;\nstatic const int bbr_cwnd_gain  = BBR_UNIT * 2;\nstatic const u32 bbr_cycle_rand = 7; \/\/ \u968f\u673a\u5316\nstatic const u32 bbr_cwnd_min_target = 4; \/\/ \u81f3\u5c11\u4fdd\u8bc14\u4e2a\u5305\u7684cwnd\nstatic const u32 bbr_full_bw_thresh = BBR_UNIT * 5 \/ 4;\nstatic const u32 bbr_full_bw_cnt = 3;\n<\/code><\/pre>\n\n\n\n<p><strong>long-term\u76f8\u5173\u7684\u4e1c\u897f<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\">\/* \"long-term\" (\"LT\") bandwidth estimator parameters... *\/\n\/* The minimum number of rounds in an LT bw sampling interval: *\/\nstatic const u32 bbr_lt_intvl_min_rtts = 4;\n\/* If lost\/delivered ratio > 20%, interval is \"lossy\" and we may be policed: *\/\nstatic const u32 bbr_lt_loss_thresh = 50;\n\/* If 2 intervals have a bw ratio &lt;= 1\/8, their bw is \"consistent\": *\/\nstatic const u32 bbr_lt_bw_ratio = BBR_UNIT \/ 8;\n\/* If 2 intervals have a bw diff &lt;= 4 Kbit\/sec their bw is \"consistent\": *\/\nstatic const u32 bbr_lt_bw_diff = 4000 \/ 8;\n\/* If we estimate we're policed, use lt_bw for this many round trips: *\/\nstatic const u32 bbr_lt_bw_max_rtts = 48;<\/code><\/pre>\n\n\n\n<p>bbr_lt_loss_thresh\uff1a\u4e22\u5305\u7387\u8fde\u7eed\u8d85\u8fc720%\uff0c\u5219\u8ba4\u4e3a\u6536\u5230\u4e86\u6d41\u91cf\u63a7\u5236\uff0c\u9700\u8981\u8fdb\u5165long-term\u6a21\u5f0f<\/p>\n\n\n\n<p><strong>ack\u805a\u79ef\u76f8\u5173\u7684\u4e1c\u897f<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\">\/* Gain factor for adding extra_acked to target cwnd: *\/\nstatic const int bbr_extra_acked_gain = BBR_UNIT;\n\/* Window length of extra_acked window. *\/\nstatic const u32 bbr_extra_acked_win_rtts = 5;\n\/* Max allowed val for ack_epoch_acked, after which sampling epoch is reset *\/\nstatic const u32 bbr_ack_epoch_acked_reset_thresh = 1U &lt;&lt; 20;\n\/* Time period for clamping cwnd increment due to ack aggregation *\/\nstatic const u32 bbr_extra_acked_max_us = 100 * 1000;\n<\/code><\/pre>\n\n\n\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E9%87%8D%E8%A6%81%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84\"><\/span>\u91cd\u8981\u6570\u636e\u7ed3\u6784<span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\">static struct tcp_congestion_ops tcp_bbr_cong_ops __read_mostly = {\n\t.flags\t\t= TCP_CONG_NON_RESTRICTED,\n\t.name\t\t= \"bbr\",\n\t.owner\t\t= THIS_MODULE,\n\t.init\t\t= bbr_init,\n\t.cong_control\t= bbr_main,\n\t.sndbuf_expand\t= bbr_sndbuf_expand,\n\t.undo_cwnd\t= bbr_undo_cwnd,\n\t.cwnd_event\t= bbr_cwnd_event,\n\t.ssthresh\t= bbr_ssthresh,\n\t.min_tso_segs\t= bbr_min_tso_segs,\n\t.get_info\t= bbr_get_info,\n\t.set_state\t= bbr_set_state,\n};\n<\/code><\/pre>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\">\/* BBR congestion control block *\/\nstruct bbr {\n\tu32\tmin_rtt_us;\t        \/* min RTT in min_rtt_win_sec window *\/\n\tu32\tmin_rtt_stamp;\t        \/* timestamp of min_rtt_us *\/\n\tu32\tprobe_rtt_done_stamp;   \/* end time for BBR_PROBE_RTT mode *\/\n\tstruct minmax bw;\t\/* Max recent delivery rate in pkts\/uS &lt;&lt; 24 *\/\n\tu32\trtt_cnt;\t    \/* count of packet-timed rounds elapsed *\/\n\tu32     next_rtt_delivered; \/* scb->tx.delivered at end of round *\/\n\tu64\tcycle_mstamp;\t     \/* time of this cycle phase start *\/\n\tu32     mode:3,\t\t     \/* current bbr_mode in state machine *\/\n\t\tprev_ca_state:3,     \/* CA state on previous ACK *\/\n\t\tpacket_conservation:1,  \/* use packet conservation? *\/\n\t\tround_start:1,\t     \/* start of packet-timed tx->ack round? *\/\n\t\tidle_restart:1,\t     \/* restarting after idle? *\/\n\t\tprobe_rtt_round_done:1,  \/* a BBR_PROBE_RTT round at 4 pkts? *\/\n\t\tunused:13,\n\t\tlt_is_sampling:1,    \/* taking long-term (\"LT\") samples now? *\/\n\t\tlt_rtt_cnt:7,\t     \/* round trips in long-term interval *\/\n\t\tlt_use_bw:1;\t     \/* use lt_bw as our bw estimate? *\/\n\tu32\tlt_bw;\t\t     \/* LT est delivery rate in pkts\/uS &lt;&lt; 24 *\/\n\tu32\tlt_last_delivered;   \/* LT intvl start: tp->delivered *\/\n\tu32\tlt_last_stamp;\t     \/* LT intvl start: tp->delivered_mstamp *\/\n\tu32\tlt_last_lost;\t     \/* LT intvl start: tp->lost *\/\n\tu32\tpacing_gain:10,\t\/* current gain for setting pacing rate *\/\n\t\tcwnd_gain:10,\t\/* current gain for setting cwnd *\/\n\t\tfull_bw_reached:1,   \/* reached full bw in Startup? *\/\n\t\tfull_bw_cnt:2,\t\/* number of rounds without large bw gains *\/\n\t\tcycle_idx:3,\t\/* current index in pacing_gain cycle array *\/\n\t\thas_seen_rtt:1, \/* have we seen an RTT sample yet? *\/\n\t\tunused_b:5;\n\tu32\tprior_cwnd;\t\/* prior cwnd upon entering loss recovery *\/\n\tu32\tfull_bw;\t\/* recent bw, to estimate if pipe is full *\/\n\n\t\/* For tracking ACK aggregation: *\/\n\tu64\tack_epoch_mstamp;\t\/* start of ACK sampling epoch *\/\n\tu16\textra_acked[2];\t\t\/* max excess data ACKed in epoch *\/\n\tu32\tack_epoch_acked:20,\t\/* packets (S)ACKed in sampling epoch *\/\n\t\textra_acked_win_rtts:5,\t\/* age of extra_acked, in round trips *\/\n\t\textra_acked_win_idx:1,\t\/* current index in extra_acked array *\/\n\t\tunused_c:6;\n};\n<\/code><\/pre>\n\n\n\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E9%87%8D%E8%A6%81%E5%87%BD%E6%95%B0\"><\/span>\u91cd\u8981\u51fd\u6570<span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_init\"><\/span>bbr_init<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>\u7c7b\u7684\u5404\u4e2a\u53d8\u91cf\u7684\u521d\u59cb\u5316\uff1b<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_main\"><\/span>bbr_main<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"c\" class=\"language-c\">static void bbr_main(struct sock *sk, const struct rate_sample *rs)\n{\n\tstruct bbr *bbr = inet_csk_ca(sk);\n\tu32 bw;\n\n\tbbr_update_model(sk, rs);\n\n\tbw = bbr_bw(sk);\n\tbbr_set_pacing_rate(sk, bw, bbr->pacing_gain);\n\tbbr_set_cwnd(sk, rs, rs->acked_sacked, bw, bbr->cwnd_gain);\n}\n<\/code><\/pre>\n\n\n\n<p>\u6bcf\u6b21\u6536\u5230ack\u540e\uff0c\u9700\u8981\u6267\u884c\u7684\u52a8\u4f5c\uff1a\u66f4\u65b0mode\uff0cbw\uff0cpacing_rate\uff0ccwnd<\/p>\n\n\n\n<p>\u5b9e\u73b0\u4e86cong_control\u65b9\u6cd5\uff0c\u8be5\u65b9\u6cd5\u5728\u5904\u7406\u597dca_state\u540e\u8c03\u7528\uff0c\u7528\u4e8e\u66f4\u65b0cwnd\u548cpacing_rate\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_sndbuf_expand\"><\/span>bbr_sndbuf_expand<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\">static u32 bbr_sndbuf_expand(struct sock *sk)\n{\n\t\/* Provision 3 * cwnd since BBR may slow-start even during recovery. *\/\n\treturn 3;\n}\n<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_undo_cwnd\"><\/span>bbr_undo_cwnd<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\">\/* In theory BBR does not need to undo the cwnd since it does not\n * always reduce cwnd on losses (see bbr_main()). Keep it for now.\n *\/\nstatic u32 bbr_undo_cwnd(struct sock *sk)\n{\n\tstruct bbr *bbr = inet_csk_ca(sk);\n\n\tbbr->full_bw = 0;   \/* spurious slow-down; reset full pipe detection *\/\n\tbbr->full_bw_cnt = 0;\n\tbbr_reset_lt_bw_sampling(sk);\n\treturn tcp_sk(sk)->snd_cwnd;\n}\n<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_ssthresh\"><\/span>bbr_ssthresh<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\">\/* Entering loss recovery, so save cwnd for when we exit or undo recovery. *\/\nstatic u32 bbr_ssthresh(struct sock *sk)\n{\n\tbbr_save_cwnd(sk);\n\treturn tcp_sk(sk)->snd_ssthresh;\n}\n<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_min_tso_segs\"><\/span>bbr_min_tso_segs<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\">\/* override sysctl_tcp_min_tso_segs *\/\nstatic u32 bbr_min_tso_segs(struct sock *sk)\n{\n\treturn sk->sk_pacing_rate &lt; (bbr_min_tso_rate >> 3) ? 1 : 2;\n}\n<\/code><\/pre>\n\n\n\n<p>tcp_min_tso_seg\uff1a\u6bcf\u4e2a TSO \u5e27\u5305\u542b\u7684\u62a5\u6587\u6bb5\u6570\u91cf\u6700\u5c0f\u503c\u3002<\/p>\n\n\n\n<p>\u5bf9\u4e8e\u4f4e\u5e26\u5bbd\u94fe\u8def\uff0ctso\u5728\u4e00\u4e2atso\u5e27\u4e2d\u5c06\u591a\u4e2a\u62a5\u6587\u6bb5\u9001\u7ed9\u7f51\u5361\uff0c\u8fd9\u6837\u53cd\u800c\u5bfc\u81f4\u4f4e\u5e26\u5bbd\u94fe\u8def\u4e0a\u7684burst\u4f20\u8f93\uff0c\u56e0\u6b64\u4f4e\u5e26\u5bbd\u94fe\u8def\u53cd\u800c\u5e94\u8be5\u9650\u5236tso\u7684\u4f7f\u7528\u3002<\/p>\n\n\n\n<p><a href=\"https:\/\/lotabout.me\/2021\/Linux-TCP-Options\/\">tcp_min_tso_segs\u53c2\u6570\u7684\u89e3\u91ca<\/a><\/p>\n\n\n\n<p><a href=\"https:\/\/lwn.net\/Articles\/564979\/\">\u5185\u6838\u4ee3\u7801\u76f8\u5173\u4fee\u6539<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_get_info\"><\/span>bbr_get_info<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>\u8fd4\u56debbr\u5185\u90e8\u72b6\u6001<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_set_state\"><\/span>bbr_set_state<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\">static void bbr_set_state(struct sock *sk, u8 new_state)\n{\n\tstruct bbr *bbr = inet_csk_ca(sk);\n\n\tif (new_state == TCP_CA_Loss) {\n\t\tstruct rate_sample rs = { .losses = 1 };\n\n\t\tbbr->prev_ca_state = TCP_CA_Loss;\n\t\tbbr->full_bw = 0;\n\t\tbbr->round_start = 1;\t\/* treat RTO like end of a round *\/\n\t\tbbr_lt_bw_sampling(sk, &amp;rs);\n\t}\n}\n<\/code><\/pre>\n\n\n\n<p>\u6539\u53d8ca_state\u65f6\u8c03\u7528\uff0cca_state\u7684\u53d6\u503c\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\">\/*\n * Sender's congestion state indicating normal or abnormal situations\n * in the last round of packets sent. The state is driven by the ACK\n * information and timer events.\n *\/\nenum tcp_ca_state {\n\t\/*\n\t * Nothing bad has been observed recently.\n\t * No apparent reordering, packet loss, or ECN marks.\n\t *\/\n\tTCP_CA_Open = 0,\n#define TCPF_CA_Open\t(1&lt;&lt;TCP_CA_Open)\n\t\/*\n\t * The sender enters disordered state when it has received DUPACKs or\n\t * SACKs in the last round of packets sent. This could be due to packet\n\t * loss or reordering but needs further information to confirm packets\n\t * have been lost.\n\t *\/\n\tTCP_CA_Disorder = 1,\n#define TCPF_CA_Disorder (1&lt;&lt;TCP_CA_Disorder)\n\t\/*\n\t * The sender enters Congestion Window Reduction (CWR) state when it\n\t * has received ACKs with ECN-ECE marks, or has experienced congestion\n\t * or packet discard on the sender host (e.g. qdisc).\n\t *\/\n\tTCP_CA_CWR = 2,\n#define TCPF_CA_CWR\t(1&lt;&lt;TCP_CA_CWR)\n\t\/*\n\t * The sender is in fast recovery and retransmitting lost packets,\n\t * typically triggered by ACK events.\n\t *\/\n\tTCP_CA_Recovery = 3,\n#define TCPF_CA_Recovery (1&lt;&lt;TCP_CA_Recovery)\n\t\/*\n\t * The sender is in loss recovery triggered by retransmission timeout.\n\t *\/\n\tTCP_CA_Loss = 4\n#define TCPF_CA_Loss\t(1&lt;&lt;TCP_CA_Loss)\n};\n<\/code><\/pre>\n\n\n\n<p>\u6240\u4ee5\u8fd9\u4e2abbr_set_state\u51fd\u6570\u7684\u4f5c\u7528\u5c31\u662f\u5728\u9047\u5230rto\u8d85\u65f6\u540e\u91cd\u65b0\u8fdb\u5165STARTUP\u3002<\/p>\n\n\n\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%86%85%E9%83%A8%E5%87%BD%E6%95%B0\"><\/span>\u5185\u90e8\u51fd\u6570<span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_save_cwnd\"><\/span>bbr_save_cwnd<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\">\/* Save \"last known good\" cwnd so we can restore it after losses or PROBE_RTT *\/\nstatic void bbr_save_cwnd(struct sock *sk)\n{\n\tstruct tcp_sock *tp = tcp_sk(sk);\n\tstruct bbr *bbr = inet_csk_ca(sk);\n\n\tif (bbr->prev_ca_state &lt; TCP_CA_Recovery &amp;&amp; bbr->mode != BBR_PROBE_RTT)\n\t\tbbr->prior_cwnd = tp->snd_cwnd;  \/* this cwnd is good enough *\/\n\telse  \/* loss recovery or BBR_PROBE_RTT have temporarily cut cwnd *\/\n\t\tbbr->prior_cwnd = max(bbr->prior_cwnd, tp->snd_cwnd);\n}\n<\/code><\/pre>\n\n\n\n<p>\u4fdd\u5b58cwnd\uff0c\u5728\u9000\u51faloss recovery\u6216\u8005probe_rtt\u7ed3\u675f\u540e\u53ef\u4ee5\u7ee7\u7eed\u4f7f\u7528\u8fd9\u4e2acwnd\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_update_model\"><\/span>bbr_update_model<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\">static void bbr_update_model(struct sock *sk, const struct rate_sample *rs)\n{\n\tbbr_update_bw(sk, rs);\n\tbbr_update_ack_aggregation(sk, rs);\n\tbbr_update_cycle_phase(sk, rs);\n\tbbr_check_full_bw_reached(sk, rs);\n\tbbr_check_drain(sk, rs);\n\tbbr_update_min_rtt(sk, rs);\n\tbbr_update_gains(sk);\n}\n<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_update_bw\"><\/span>bbr_update_bw<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>\u66f4\u65b0round\u6570\uff0c\u4ee5\u53ca\u5e26\u5bbd\u91c7\u6837\u503c(\u5305\u62eclong-term\u6a21\u5f0f\u7684\u5e26\u5bbd\u91c7\u6837)\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_update_ack_aggregation\"><\/span>bbr_update_ack_aggregation<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>\u7528extra_acked[0]\u548cextra_acked[1]\u8868\u793a\u6700\u8fd11-5\u8fd95\u4e2a\u5468\u671f\u548c\u6700\u8fd16-10\u8fd95\u4e2a\u5468\u671f\u5185\u7684\u6700\u5927ack\u805a\u79ef\uff0c\u53ea\u6709\u5728\u6bcf\u4e2around\u7ed3\u675f\u7684\u90a3\u4e00\u4e2aack\u624d\u9700\u8981\u66f4\u65b0ack\u805a\u79ef\u7a0b\u5ea6\u3002\u805a\u79ef\u7a0b\u5ea6\u53d6extra_acked[0]\u548cextra_acked[1]\u4e2d\u7684\u6700\u5927\u503c\u3002<\/p>\n\n\n\n<p>\u5982\u679c\u5b9e\u9645ack\u7684\u5b57\u8282\u6570\u5c0f\u4e8e\u7b49\u4e8eexpected_acked\u6216\u8005\u8fdc\u5927\u4e8eexpected_acked(\u8d85\u8fc72^20)\uff0c\u90a3\u4e48\u8981\u91cd\u7f6e\u8ddf\u8e2aextra_acked\u7684round\u3002<\/p>\n\n\n\n<p>extra_acked[0\/1]\u4e0d\u80fd\u8d85\u8fc7\u5f53\u524dsnd_cwnd\u3002<\/p>\n\n\n\n<p>\u6700\u540e\u5728\u8ba1\u7b97target_cwnd\u65f6\uff0cextra_acked\u4e0d\u80fd\u8d85\u8fc7bw * bbr_extra_acked_max_us(100ms)\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_update_cycle_phase\"><\/span>bbr_update_cycle_phase<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>\u5bf9\u4e8epacing_gain\u7b49\u4e8e1\u7684\u9636\u6bb5(PROBE_BW\u4e2d\u76846\u4e2a\u5e73\u7a33\u53d1\u9001\u9636\u6bb5)\uff0c\u9700\u8981\u53d1\u8db31\u4e2artt\u65f6\u95f4(\u6309wall clock time\u7b97)\u624d\u53ef\u4ee5\u8fdb\u5165\u4e0b\u4e00\u4e2a\u9636\u6bb5\u3002<\/p>\n\n\n\n<p>\u5bf9\u4e8epacing_gain\u5927\u4e8e1\u7684\u9636\u6bb5(STARTUP\u548cPROBE_BW\u4e2d\u7684\u4e0a\u5347\u63a2\u6d4b\u9636\u6bb5)\uff0c\u9700\u8981\u540c\u65f6\u6ee1\u8db32\u4e2a\u6761\u4ef6\u624d\u53ef\u4ee5\u8fdb\u5165\u4e0b\u4e00\u4e2a\u9636\u6bb5\uff1aa.\u6301\u7eed\u65f6\u95f4\u8fbe\u52301\u4e2artt(\u6309wall clock time\u7b97)\uff0cb.\u51fa\u73b0\u4e22\u5305\u6216\u8005bif\u8fbe\u5230pacing_gain * BDP(bw*min_rtt)\u3002\u6ce8\u610f\u7b2c2\u4e2a\u6761\u4ef6\u91cc\u5217\u7684\u662fpacing_gain\u800c\u4e0d\u662fcwnd_gain\u3002<\/p>\n\n\n\n<p>\u5bf9\u4e8epacing_gain\u5c0f\u4e8e1\u7684\u9636\u6bb5(DRAIN\u548cPROBE_BW\u4e2d\u7684\u4e0b\u964d\u9636\u6bb5)\uff0c\u53ea\u8981\u6ee1\u8db32\u4e2a\u6761\u4ef6\u4e2d\u4efb\u610f1\u4e2a\u5373\u53ef\u8fdb\u5165\u4e0b\u4e00\u4e2a\u9636\u6bb5\uff1aa.\u6301\u7eed\u65f6\u95f4\u8fbe\u52301\u4e2artt(\u6309wall clock time\u7b97)\uff0cb.bif\u5c0f\u4e8e\u7b49\u4e8eBDP(bw*min_rtt)\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_check_full_bw_reached\"><\/span>bbr_check_full_bw_reached<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>\u67093\u4e2anon-applimited round\u5e26\u5bbd\u589e\u957f\u90fd\u6ca1\u6709\u8fbe\u523025%\uff0c\u90a3\u4e48\u5c31\u4efb\u52a1startup\u5df2\u7ecf\u63a2\u6d4b\u5230\u6700\u5927\u5e26\u5bbd\u4e86\u3002<span class=\"has-inline-color has-luminous-vivid-amber-color\">\u4e3a\u4ec0\u4e48\u662f3\u4e2around\uff1f<\/span>\u8fd9\u4e2a\u51fd\u6570\u7684\u6ce8\u91ca\u662f\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"cpp\" class=\"language-cpp\">\/* Estimate when the pipe is full, using the change in delivery rate: BBR\n * estimates that STARTUP filled the pipe if the estimated bw hasn't changed by\n * at least bbr_full_bw_thresh (25%) after bbr_full_bw_cnt (3) non-app-limited\n * rounds. Why 3 rounds: 1: rwin autotuning grows the rwin, 2: we fill the\n * higher rwin, 3: we get higher delivery rate samples. Or transient\n * cross-traffic or radio noise can go away. CUBIC Hystart shares a similar\n * design goal, but uses delay and inter-ACK spacing instead of bandwidth.\n *\/\n<\/code><\/pre>\n\n\n\n<p>\u5148\u75281\u4e2around\u6765\u8ba9\u63a5\u6536\u7aef\u52a8\u6001\u8c03\u6574receive window\uff0c\u518d\u75281\u4e2around\u586b\u6ee1\u589e\u957f\u540e\u7684receive window\uff0c\u518d\u75281\u4e2around\u83b7\u53d6\u66f4\u9ad8\u7684delivery rate\u3002<\/p>\n\n\n\n<p>Linux\u4e2d\u63a7\u5236receive window\u7684auto tuning\u7684\u53c2\u6570\uff1a<\/p>\n\n\n\n<p>net.ipv4.tcp_moderate_rcvbuf<\/p>\n\n\n\n<p><span class=\"has-inline-color has-vivid-red-color\">\u90a3\u4e48\u5bf9\u4e8e\u6ca1\u6709\u5b9e\u73b0auto-tuning\u7684\u63a5\u6536\u7aef\u6765\u8bf4\uff0c\u5176\u5b9e\u4e0d\u9700\u8981\u7b49\u5f853\u4e2around\uff0c2\u4e2around\u5c31\u53ef\u4ee5\u4e86\uff1f<\/span><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_check_drain\"><\/span>bbr_check_drain<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>STARTUP\u4e4b\u540e\u7684\u6392\u7a7a\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_update_min_rtt\"><\/span>bbr_update_min_rtt<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>\u6536\u5230ack\u540e\u68c0\u67e5min_rtt\u662f\u5426\u8fc7\u671f(10s)\uff0c\u5982\u679c\u8fc7\u671f\u5219\u9700\u8981\u8fdb\u5165PROBE_RTT\u72b6\u6001\uff0c\u81f3\u5c11\u6301\u7eedmax(200ms,1RTT)\u65f6\u95f4\u3002\u5176\u4e2d1RTT\u662f\u901a\u8fc7\u6536\u5230\u8fdb\u5165PROBE_RTT\u53d1\u51fa\u7684\u90a3\u4e2a\u5305\u6765\u4fdd\u8bc1\u7684\u3002<\/p>\n\n\n\n<p>\u5185\u6838\u4ee3\u7801\u5b9e\u73b0\u4f3c\u4e4e\u6709\u70b9\u95ee\u9898\uff0c\u5373\u4f7f\u5f53\u524d\u7684rate_sample\u91cc\u5df2\u7ecf\u5305\u542b\u4e86\u4e00\u4e2a\u66f4\u5c0f\u7684rtt\uff0c\u4f46\u662f\u53ea\u8981filter_delivered\u4e3atrue\u5c31\u4f1a\u8fdb\u5165PROBE_RTT\uff0c\u66f4\u597d\u7684\u5b9e\u73b0\u5e94\u8be5\u662f\u68c0\u6d4b\u5230\u4e00\u4e2a\u66f4\u5c0f\u7684rtt\u540e\u5c31\u4e0d\u518d\u8fdb\u5165PROBE_RTT\uff1f<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"bbr_update_gains\"><\/span>bbr_update_gains<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>\u8ddf\u636ebbr\u6a21\u578b\u5f53\u524d\u9636\u6bb5\u8bbe\u7f6e\u53d1\u9001\u6570\u636e\u7684pacing_gain\u548ccwnd_gain\uff0c\u5bf9\u4e8elong-term\u6a21\u5f0f\uff0cPROBE_BW\u7684pacing_gain\u662f1\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u6e90\u7801 \u7248\u672c5.16-rc3 \u6838\u5fc3\u7b97\u6cd5 &nbsp;&nbsp;&nbsp;On each ACK, update our model of the network path: &nbsp;&nbsp;&#46;&#46;&#46;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10],"tags":[66,37,28],"class_list":["post-687","post","type-post","status-publish","format-standard","hentry","category-10","tag-bbr","tag-kernel","tag-28"],"_links":{"self":[{"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=\/wp\/v2\/posts\/687","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=687"}],"version-history":[{"count":6,"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=\/wp\/v2\/posts\/687\/revisions"}],"predecessor-version":[{"id":696,"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=\/wp\/v2\/posts\/687\/revisions\/696"}],"wp:attachment":[{"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=687"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=687"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=687"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}