From 6b31b28a441c9ba33889f88ac1d9451ed9532ada Mon Sep 17 00:00:00 2001 From: Thomas Graf Date: Sat, 5 Nov 2005 21:14:05 +0100 Subject: [PATCH] [PKT_SCHED]: RED: Use new generic red interface Simplifies code a lot by separating the red algorithm and the queueing logic. We now differentiate between probability marks and forced marks but sum them together again to not break backwards compatibility. Signed-off-by: Thomas Graf Signed-off-by: Arnaldo Carvalho de Melo --- net/sched/sch_red.c | 321 ++++++++++---------------------------------- 1 file changed, 74 insertions(+), 247 deletions(-) diff --git a/net/sched/sch_red.c b/net/sched/sch_red.c index 7845d045ee..0dabcc9091 100644 --- a/net/sched/sch_red.c +++ b/net/sched/sch_red.c @@ -41,44 +41,10 @@ #include #include #include +#include -/* Random Early Detection (RED) algorithm. - ======================================= - - Source: Sally Floyd and Van Jacobson, "Random Early Detection Gateways - for Congestion Avoidance", 1993, IEEE/ACM Transactions on Networking. - - This file codes a "divisionless" version of RED algorithm - as written down in Fig.17 of the paper. - -Short description. ------------------- - - When a new packet arrives we calculate the average queue length: - - avg = (1-W)*avg + W*current_queue_len, - - W is the filter time constant (chosen as 2^(-Wlog)), it controls - the inertia of the algorithm. To allow larger bursts, W should be - decreased. - - if (avg > th_max) -> packet marked (dropped). - if (avg < th_min) -> packet passes. - if (th_min < avg < th_max) we calculate probability: - - Pb = max_P * (avg - th_min)/(th_max-th_min) - - and mark (drop) packet with this probability. - Pb changes from 0 (at avg==th_min) to max_P (avg==th_max). - max_P should be small (not 1), usually 0.01..0.02 is good value. - - max_P is chosen as a number, so that max_P/(th_max-th_min) - is a negative power of two in order arithmetics to contain - only shifts. - - - Parameters, settable by user: +/* Parameters, settable by user: ----------------------------- limit - bytes (must be > qth_max + burst) @@ -89,92 +55,19 @@ Short description. arbitrarily high (well, less than ram size) Really, this limit will never be reached if RED works correctly. - - qth_min - bytes (should be < qth_max/2) - qth_max - bytes (should be at least 2*qth_min and less limit) - Wlog - bits (<32) log(1/W). - Plog - bits (<32) - - Plog is related to max_P by formula: - - max_P = (qth_max-qth_min)/2^Plog; - - F.e. if qth_max=128K and qth_min=32K, then Plog=22 - corresponds to max_P=0.02 - - Scell_log - Stab - - Lookup table for log((1-W)^(t/t_ave). - - -NOTES: - -Upper bound on W. ------------------ - - If you want to allow bursts of L packets of size S, - you should choose W: - - L + 1 - th_min/S < (1-(1-W)^L)/W - - th_min/S = 32 th_min/S = 4 - - log(W) L - -1 33 - -2 35 - -3 39 - -4 46 - -5 57 - -6 75 - -7 101 - -8 135 - -9 190 - etc. */ struct red_sched_data { -/* Parameters */ - u32 limit; /* HARD maximal queue length */ - u32 qth_min; /* Min average length threshold: A scaled */ - u32 qth_max; /* Max average length threshold: A scaled */ - u32 Rmask; - u32 Scell_max; - unsigned char flags; - char Wlog; /* log(W) */ - char Plog; /* random number bits */ - char Scell_log; - u8 Stab[256]; - -/* Variables */ - unsigned long qave; /* Average queue length: A scaled */ - int qcount; /* Packets since last random number generation */ - u32 qR; /* Cached random number */ - - psched_time_t qidlestart; /* Start of idle period */ - struct tc_red_xstats st; + u32 limit; /* HARD maximal queue length */ + unsigned char flags; + struct red_parms parms; + struct red_stats stats; }; -static int red_ecn_mark(struct sk_buff *skb) +static inline int red_use_ecn(struct red_sched_data *q) { - if (skb->nh.raw + 20 > skb->tail) - return 0; - - switch (skb->protocol) { - case __constant_htons(ETH_P_IP): - if (INET_ECN_is_not_ect(skb->nh.iph->tos)) - return 0; - IP_ECN_set_ce(skb->nh.iph); - return 1; - case __constant_htons(ETH_P_IPV6): - if (INET_ECN_is_not_ect(ipv6_get_dsfield(skb->nh.ipv6h))) - return 0; - IP6_ECN_set_ce(skb->nh.ipv6h); - return 1; - default: - return 0; - } + return q->flags & TC_RED_ECN; } static int @@ -182,119 +75,50 @@ red_enqueue(struct sk_buff *skb, struct Qdisc* sch) { struct red_sched_data *q = qdisc_priv(sch); - psched_time_t now; + q->parms.qavg = red_calc_qavg(&q->parms, sch->qstats.backlog); - if (!PSCHED_IS_PASTPERFECT(q->qidlestart)) { - long us_idle; - int shift; + if (red_is_idling(&q->parms)) + red_end_of_idle_period(&q->parms); - PSCHED_GET_TIME(now); - us_idle = PSCHED_TDIFF_SAFE(now, q->qidlestart, q->Scell_max); - PSCHED_SET_PASTPERFECT(q->qidlestart); + switch (red_action(&q->parms, q->parms.qavg)) { + case RED_DONT_MARK: + break; -/* - The problem: ideally, average length queue recalcultion should - be done over constant clock intervals. This is too expensive, so that - the calculation is driven by outgoing packets. - When the queue is idle we have to model this clock by hand. - - SF+VJ proposed to "generate" m = idletime/(average_pkt_size/bandwidth) - dummy packets as a burst after idle time, i.e. - - q->qave *= (1-W)^m - - This is an apparently overcomplicated solution (f.e. we have to precompute - a table to make this calculation in reasonable time) - I believe that a simpler model may be used here, - but it is field for experiments. -*/ - shift = q->Stab[us_idle>>q->Scell_log]; - - if (shift) { - q->qave >>= shift; - } else { - /* Approximate initial part of exponent - with linear function: - (1-W)^m ~= 1-mW + ... - - Seems, it is the best solution to - problem of too coarce exponent tabulation. - */ - - us_idle = (q->qave * us_idle)>>q->Scell_log; - if (us_idle < q->qave/2) - q->qave -= us_idle; - else - q->qave >>= 1; - } - } else { - q->qave += sch->qstats.backlog - (q->qave >> q->Wlog); - /* NOTE: - q->qave is fixed point number with point at Wlog. - The formulae above is equvalent to floating point - version: - - qave = qave*(1-W) + sch->qstats.backlog*W; - --ANK (980924) - */ - } + case RED_PROB_MARK: + sch->qstats.overlimits++; + if (!red_use_ecn(q) || !INET_ECN_set_ce(skb)) { + q->stats.prob_drop++; + goto congestion_drop; + } - if (q->qave < q->qth_min) { - q->qcount = -1; -enqueue: - if (sch->qstats.backlog + skb->len <= q->limit) { - __skb_queue_tail(&sch->q, skb); - sch->qstats.backlog += skb->len; - sch->bstats.bytes += skb->len; - sch->bstats.packets++; - return NET_XMIT_SUCCESS; - } else { - q->st.pdrop++; - } - kfree_skb(skb); - sch->qstats.drops++; - return NET_XMIT_DROP; - } - if (q->qave >= q->qth_max) { - q->qcount = -1; - sch->qstats.overlimits++; -mark: - if (!(q->flags&TC_RED_ECN) || !red_ecn_mark(skb)) { - q->st.early++; - goto drop; - } - q->st.marked++; - goto enqueue; + q->stats.prob_mark++; + break; + + case RED_HARD_MARK: + sch->qstats.overlimits++; + if (!red_use_ecn(q) || !INET_ECN_set_ce(skb)) { + q->stats.forced_drop++; + goto congestion_drop; + } + + q->stats.forced_mark++; + break; } - if (++q->qcount) { - /* The formula used below causes questions. - - OK. qR is random number in the interval 0..Rmask - i.e. 0..(2^Plog). If we used floating point - arithmetics, it would be: (2^Plog)*rnd_num, - where rnd_num is less 1. - - Taking into account, that qave have fixed - point at Wlog, and Plog is related to max_P by - max_P = (qth_max-qth_min)/2^Plog; two lines - below have the following floating point equivalent: - - max_P*(qave - qth_min)/(qth_max-qth_min) < rnd/qcount - - Any questions? --ANK (980924) - */ - if (((q->qave - q->qth_min)>>q->Wlog)*q->qcount < q->qR) - goto enqueue; - q->qcount = 0; - q->qR = net_random()&q->Rmask; - sch->qstats.overlimits++; - goto mark; + if (sch->qstats.backlog + skb->len <= q->limit) { + __skb_queue_tail(&sch->q, skb); + sch->qstats.backlog += skb->len; + sch->bstats.bytes += skb->len; + sch->bstats.packets++; + return NET_XMIT_SUCCESS; } - q->qR = net_random()&q->Rmask; - goto enqueue; -drop: + q->stats.pdrop++; + kfree_skb(skb); + sch->qstats.drops++; + return NET_XMIT_DROP; + +congestion_drop: kfree_skb(skb); sch->qstats.drops++; return NET_XMIT_CN; @@ -305,7 +129,8 @@ red_requeue(struct sk_buff *skb, struct Qdisc* sch) { struct red_sched_data *q = qdisc_priv(sch); - PSCHED_SET_PASTPERFECT(q->qidlestart); + if (red_is_idling(&q->parms)) + red_end_of_idle_period(&q->parms); __skb_queue_head(&sch->q, skb); sch->qstats.backlog += skb->len; @@ -324,7 +149,8 @@ red_dequeue(struct Qdisc* sch) sch->qstats.backlog -= skb->len; return skb; } - PSCHED_GET_TIME(q->qidlestart); + + red_start_of_idle_period(&q->parms); return NULL; } @@ -338,11 +164,12 @@ static unsigned int red_drop(struct Qdisc* sch) unsigned int len = skb->len; sch->qstats.backlog -= len; sch->qstats.drops++; - q->st.other++; + q->stats.other++; kfree_skb(skb); return len; } - PSCHED_GET_TIME(q->qidlestart); + + red_start_of_idle_period(&q->parms); return 0; } @@ -352,9 +179,7 @@ static void red_reset(struct Qdisc* sch) __skb_queue_purge(&sch->q); sch->qstats.backlog = 0; - PSCHED_SET_PASTPERFECT(q->qidlestart); - q->qave = 0; - q->qcount = -1; + red_restart(&q->parms); } static int red_change(struct Qdisc *sch, struct rtattr *opt) @@ -374,19 +199,14 @@ static int red_change(struct Qdisc *sch, struct rtattr *opt) sch_tree_lock(sch); q->flags = ctl->flags; - q->Wlog = ctl->Wlog; - q->Plog = ctl->Plog; - q->Rmask = ctl->Plog < 32 ? ((1<Plog) - 1) : ~0UL; - q->Scell_log = ctl->Scell_log; - q->Scell_max = (255<Scell_log); - q->qth_min = ctl->qth_min<Wlog; - q->qth_max = ctl->qth_max<Wlog; q->limit = ctl->limit; - memcpy(q->Stab, RTA_DATA(tb[TCA_RED_STAB-1]), 256); - q->qcount = -1; + red_set_parms(&q->parms, ctl->qth_min, ctl->qth_max, ctl->Wlog, + ctl->Plog, ctl->Scell_log, + RTA_DATA(tb[TCA_RED_STAB-1])); + if (skb_queue_empty(&sch->q)) - PSCHED_SET_PASTPERFECT(q->qidlestart); + red_end_of_idle_period(&q->parms); sch_tree_unlock(sch); return 0; } @@ -401,17 +221,18 @@ static int red_dump(struct Qdisc *sch, struct sk_buff *skb) struct red_sched_data *q = qdisc_priv(sch); unsigned char *b = skb->tail; struct rtattr *rta; - struct tc_red_qopt opt; + struct tc_red_qopt opt = { + .limit = q->limit, + .flags = q->flags, + .qth_min = q->parms.qth_min >> q->parms.Wlog, + .qth_max = q->parms.qth_max >> q->parms.Wlog, + .Wlog = q->parms.Wlog, + .Plog = q->parms.Plog, + .Scell_log = q->parms.Scell_log, + }; rta = (struct rtattr*)b; RTA_PUT(skb, TCA_OPTIONS, 0, NULL); - opt.limit = q->limit; - opt.qth_min = q->qth_min>>q->Wlog; - opt.qth_max = q->qth_max>>q->Wlog; - opt.Wlog = q->Wlog; - opt.Plog = q->Plog; - opt.Scell_log = q->Scell_log; - opt.flags = q->flags; RTA_PUT(skb, TCA_RED_PARMS, sizeof(opt), &opt); rta->rta_len = skb->tail - b; @@ -425,8 +246,14 @@ rtattr_failure: static int red_dump_stats(struct Qdisc *sch, struct gnet_dump *d) { struct red_sched_data *q = qdisc_priv(sch); - - return gnet_stats_copy_app(d, &q->st, sizeof(q->st)); + struct tc_red_xstats st = { + .early = q->stats.prob_drop + q->stats.forced_drop, + .pdrop = q->stats.pdrop, + .other = q->stats.other, + .marked = q->stats.prob_mark + q->stats.forced_mark, + }; + + return gnet_stats_copy_app(d, &st, sizeof(st)); } static struct Qdisc_ops red_qdisc_ops = { -- 2.39.5