From 0a9fe5c375b57fab6d18ed0a6a7f935eefb09db3 Mon Sep 17 00:00:00 2001 From: Yousuk Seung Date: Wed, 27 Jun 2018 10:32:19 -0700 Subject: [PATCH] netem: slotting with non-uniform distribution Extend slotting with support for non-uniform distributions. This is similar to netem's non-uniform distribution delay feature. Commit f043efeae2f1 ("netem: support delivering packets in delayed time slots") added the slotting feature to approximate the behaviors of media with packet aggregation but only supported a uniform distribution for delays between transmission attempts. Tests with TCP BBR with emulated wifi links with non-uniform distributions produced more useful results. Syntax: slot dist DISTRIBUTION DELAY JITTER [packets MAX_PACKETS] \ [bytes MAX_BYTES] The syntax and use of the distribution table is the same as in the non-uniform distribution delay feature. A file DISTRIBUTION must be present in TC_LIB_DIR (e.g. /usr/lib/tc) containing numbers scaled by NETEM_DIST_SCALE. A random value x is selected from the table and it takes DELAY + ( x * JITTER ) as delay. Correlation between values is not supported. Examples: Normal distribution delay with mean = 800us and stdev = 100us. > tc qdisc add dev eth0 root netem slot dist normal 800us 100us Optionally set the max slot size in bytes and/or packets. > tc qdisc add dev eth0 root netem slot dist normal 800us 100us \ bytes 64k packets 42 Signed-off-by: Yousuk Seung Acked-by: Eric Dumazet Acked-by: Neal Cardwell Signed-off-by: David S. Miller --- include/uapi/linux/pkt_sched.h | 3 ++ net/sched/sch_netem.c | 73 ++++++++++++++++++++++++++++-------------- 2 files changed, 52 insertions(+), 24 deletions(-) diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h index 37b5096ae97b..bad3c03bcf43 100644 --- a/include/uapi/linux/pkt_sched.h +++ b/include/uapi/linux/pkt_sched.h @@ -539,6 +539,7 @@ enum { TCA_NETEM_LATENCY64, TCA_NETEM_JITTER64, TCA_NETEM_SLOT, + TCA_NETEM_SLOT_DIST, __TCA_NETEM_MAX, }; @@ -581,6 +582,8 @@ struct tc_netem_slot { __s64 max_delay; __s32 max_packets; __s32 max_bytes; + __s64 dist_delay; /* nsec */ + __s64 dist_jitter; /* nsec */ }; enum { diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index 7d6801fc5340..ad18a2052416 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -68,6 +68,11 @@ Fabio Ludovici */ +struct disttable { + u32 size; + s16 table[0]; +}; + struct netem_sched_data { /* internal t(ime)fifo qdisc uses t_root and sch->limit */ struct rb_root t_root; @@ -99,10 +104,7 @@ struct netem_sched_data { u32 rho; } delay_cor, loss_cor, dup_cor, reorder_cor, corrupt_cor; - struct disttable { - u32 size; - s16 table[0]; - } *delay_dist; + struct disttable *delay_dist; enum { CLG_RANDOM, @@ -142,6 +144,7 @@ struct netem_sched_data { s32 bytes_left; } slot; + struct disttable *slot_dist; }; /* Time stamp put into socket buffer control block @@ -180,7 +183,7 @@ static u32 get_crandom(struct crndstate *state) u64 value, rho; unsigned long answer; - if (state->rho == 0) /* no correlation */ + if (!state || state->rho == 0) /* no correlation */ return prandom_u32(); value = prandom_u32(); @@ -601,10 +604,19 @@ finish_segs: static void get_slot_next(struct netem_sched_data *q, u64 now) { - q->slot.slot_next = now + q->slot_config.min_delay + - (prandom_u32() * - (q->slot_config.max_delay - - q->slot_config.min_delay) >> 32); + s64 next_delay; + + if (!q->slot_dist) + next_delay = q->slot_config.min_delay + + (prandom_u32() * + (q->slot_config.max_delay - + q->slot_config.min_delay) >> 32); + else + next_delay = tabledist(q->slot_config.dist_delay, + (s32)(q->slot_config.dist_jitter), + NULL, q->slot_dist); + + q->slot.slot_next = now + next_delay; q->slot.packets_left = q->slot_config.max_packets; q->slot.bytes_left = q->slot_config.max_bytes; } @@ -721,9 +733,9 @@ static void dist_free(struct disttable *d) * signed 16 bit values. */ -static int get_dist_table(struct Qdisc *sch, const struct nlattr *attr) +static int get_dist_table(struct Qdisc *sch, struct disttable **tbl, + const struct nlattr *attr) { - struct netem_sched_data *q = qdisc_priv(sch); size_t n = nla_len(attr)/sizeof(__s16); const __s16 *data = nla_data(attr); spinlock_t *root_lock; @@ -744,7 +756,7 @@ static int get_dist_table(struct Qdisc *sch, const struct nlattr *attr) root_lock = qdisc_root_sleeping_lock(sch); spin_lock_bh(root_lock); - swap(q->delay_dist, d); + swap(*tbl, d); spin_unlock_bh(root_lock); dist_free(d); @@ -762,7 +774,8 @@ static void get_slot(struct netem_sched_data *q, const struct nlattr *attr) q->slot_config.max_bytes = INT_MAX; q->slot.packets_left = q->slot_config.max_packets; q->slot.bytes_left = q->slot_config.max_bytes; - if (q->slot_config.min_delay | q->slot_config.max_delay) + if (q->slot_config.min_delay | q->slot_config.max_delay | + q->slot_config.dist_jitter) q->slot.slot_next = ktime_get_ns(); else q->slot.slot_next = 0; @@ -926,16 +939,17 @@ static int netem_change(struct Qdisc *sch, struct nlattr *opt, } if (tb[TCA_NETEM_DELAY_DIST]) { - ret = get_dist_table(sch, tb[TCA_NETEM_DELAY_DIST]); - if (ret) { - /* recover clg and loss_model, in case of - * q->clg and q->loss_model were modified - * in get_loss_clg() - */ - q->clg = old_clg; - q->loss_model = old_loss_model; - return ret; - } + ret = get_dist_table(sch, &q->delay_dist, + tb[TCA_NETEM_DELAY_DIST]); + if (ret) + goto get_table_failure; + } + + if (tb[TCA_NETEM_SLOT_DIST]) { + ret = get_dist_table(sch, &q->slot_dist, + tb[TCA_NETEM_SLOT_DIST]); + if (ret) + goto get_table_failure; } sch->limit = qopt->limit; @@ -983,6 +997,15 @@ static int netem_change(struct Qdisc *sch, struct nlattr *opt, get_slot(q, tb[TCA_NETEM_SLOT]); return ret; + +get_table_failure: + /* recover clg and loss_model, in case of + * q->clg and q->loss_model were modified + * in get_loss_clg() + */ + q->clg = old_clg; + q->loss_model = old_loss_model; + return ret; } static int netem_init(struct Qdisc *sch, struct nlattr *opt, @@ -1011,6 +1034,7 @@ static void netem_destroy(struct Qdisc *sch) if (q->qdisc) qdisc_destroy(q->qdisc); dist_free(q->delay_dist); + dist_free(q->slot_dist); } static int dump_loss_model(const struct netem_sched_data *q, @@ -1127,7 +1151,8 @@ static int netem_dump(struct Qdisc *sch, struct sk_buff *skb) if (dump_loss_model(q, skb) != 0) goto nla_put_failure; - if (q->slot_config.min_delay | q->slot_config.max_delay) { + if (q->slot_config.min_delay | q->slot_config.max_delay | + q->slot_config.dist_jitter) { slot = q->slot_config; if (slot.max_packets == INT_MAX) slot.max_packets = 0; -- 2.11.0