The HTB qdisc has a compile time option, HTB_HYSTERESIS, that trades accuracy of traffic classification for CPU time. These patches change hysteresis to be a runtime option under the control of "tc".
The effects of HYSTERESIS on HTB's accuracy are significant (see chapter 7, section 7.3.1, pp 69-70 in Jesper Brouer's thesis: http://www.adsl-optimizer.dk/thesis/ ), whereas HTB's CPU usage on modern machines using broadband links is minimal. Currently HYSTERESIS is on by default, and requires a kernel re-compile to change. Altering it to be a runtime option will make life easier for the bulk of its users. Further documentation on the patch and its usage can be found here: http://www.stuart.id.au/russell/files/tc/tc-atm Signed-off-by: Russell Stuart <[EMAIL PROTECTED]> Signed-off-by: Jesper Dangaard Brouer <[EMAIL PROTECTED]> --- diff -Nurp iproute2.orig/include/linux/pkt_sched.h iproute2/include/linux/pkt_sched.h --- iproute2.orig/include/linux/pkt_sched.h 2006-06-13 11:53:27.000000000 +1000 +++ iproute2/include/linux/pkt_sched.h 2006-06-13 11:54:50.000000000 +1000 @@ -232,6 +232,10 @@ struct tc_gred_sopt #define TC_HTB_MAXDEPTH 8 #define TC_HTB_PROTOVER 3 /* the same as HTB and TC's major */ +struct tc_htb_hopt +{ + __u32 nohyst; +}; struct tc_htb_opt { struct tc_ratespec rate; @@ -259,6 +263,7 @@ enum TCA_HTB_INIT, TCA_HTB_CTAB, TCA_HTB_RTAB, + TCA_HTB_NOHYST, __TCA_HTB_MAX, }; diff -Nurp iproute2.orig/tc/q_htb.c iproute2/tc/q_htb.c --- iproute2.orig/tc/q_htb.c 2006-06-13 11:53:27.000000000 +1000 +++ iproute2/tc/q_htb.c 2006-06-13 11:54:50.000000000 +1000 @@ -35,7 +35,7 @@ static void explain(void) " r2q DRR quantums are computed as rate in Bps/r2q {10}\n" " debug string of 16 numbers each 0-3 {0}\n\n" "... class add ... htb rate R1 [burst B1] [mpu B] [overhead O] [atm]\n" - " [prio P] [slot S] [pslot PS]\n" + " [prio P] [slot S] [pslot PS] [nohyst]\n" " [ceil R2] [cburst B2] [mtu MTU] [quantum Q]\n" " rate rate allocated to this class (class can still borrow)\n" " burst max bytes burst which can be accumulated during idle period {computed}\n" @@ -46,6 +46,7 @@ static void explain(void) " cburst burst but for ceil {computed}\n" " mtu max packet size we create rate map for {1600}\n" " prio priority of leaf; lower are served first {0}\n" + " nohyst disable hysteresis (heavier on CPU but more accurate)\n" " quantum how much bytes to serve from leaf at once {use r2q}\n" "\nTC HTB version %d.%d\n",HTB_TC_VER>>16,HTB_TC_VER&0xffff ); @@ -104,6 +105,7 @@ static int htb_parse_class_opt(struct qd { int ok=0; struct tc_htb_opt opt; + struct tc_htb_hopt hopt; __u32 rtab[256],ctab[256]; unsigned buffer=0,cbuffer=0; int cell_log=-1,ccell_log = -1; @@ -114,6 +116,7 @@ static int htb_parse_class_opt(struct qd struct rtattr *tail; memset(&opt, 0, sizeof(opt)); mtu = 1600; /* eth packet len */ + memset(&hopt, 0, sizeof(hopt)); while (argc > 0) { if (matches(*argv, "prio") == 0) { @@ -132,6 +135,8 @@ static int htb_parse_class_opt(struct qd if (get_u8(&mpu8, *argv, 10)) { explain1("mpu"); return -1; } + } else if (matches(*argv, "nohyst") == 0) { + hopt.nohyst = 1; } else if (matches(*argv, "overhead") == 0) { NEXT_ARG(); if (get_s8(&overhead, *argv, 10)) { @@ -221,14 +226,16 @@ static int htb_parse_class_opt(struct qd addattr_l(n, 2024, TCA_HTB_PARMS, &opt, sizeof(opt)); addattr_l(n, 3024, TCA_HTB_RTAB, rtab, 1024); addattr_l(n, 4024, TCA_HTB_CTAB, ctab, 1024); + addattr_l(n, 5024, TCA_HTB_NOHYST, &hopt, sizeof(hopt)); tail->rta_len = (void *) NLMSG_TAIL(n) - (void *) tail; return 0; } static int htb_print_opt(struct qdisc_util *qu, FILE *f, struct rtattr *opt) { - struct rtattr *tb[TCA_HTB_RTAB+1]; + struct rtattr *tb[TCA_HTB_MAX+1]; struct tc_htb_opt *hopt; + struct tc_htb_hopt *uhopt; struct tc_htb_glob *gopt; double buffer,cbuffer; SPRINT_BUF(b1); @@ -238,7 +245,7 @@ static int htb_print_opt(struct qdisc_ut if (opt == NULL) return 0; - parse_rtattr_nested(tb, TCA_HTB_RTAB, opt); + parse_rtattr_nested(tb, TCA_HTB_MAX, opt); if (tb[TCA_HTB_PARMS]) { @@ -278,6 +285,13 @@ static int htb_print_opt(struct qdisc_ut fprintf(f, "buffer [%08x] cbuffer [%08x] ", hopt->buffer,hopt->cbuffer); } + if (tb[TCA_HTB_NOHYST]) { + uhopt = RTA_DATA(tb[TCA_HTB_NOHYST]); + if (RTA_PAYLOAD(tb[TCA_HTB_NOHYST]) < sizeof(*uhopt)) return -1; + + if (uhopt->nohyst) + fprintf(f, "nohyst "); + } if (tb[TCA_HTB_INIT]) { gopt = RTA_DATA(tb[TCA_HTB_INIT]); if (RTA_PAYLOAD(tb[TCA_HTB_INIT]) < sizeof(*gopt)) return -1;
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