diff options
author | Eric Dumazet <edumazet@google.com> | 2023-10-02 16:17:37 +0300 |
---|---|---|
committer | Paolo Abeni <pabeni@redhat.com> | 2023-10-05 14:27:39 +0300 |
commit | 29f834aa326e659ed354c406056e94ea3d29706a (patch) | |
tree | 406f106492820dd48661924dfb5e3aea69a2f887 /net/sched/sch_fq.c | |
parent | 5579ee462dfe768297563a6083e21df52c3ad856 (diff) | |
download | linux-29f834aa326e659ed354c406056e94ea3d29706a.tar.xz |
net_sched: sch_fq: add 3 bands and WRR scheduling
Before Google adopted FQ for its production servers,
we had to ensure AF4 packets would get a higher share
than BE1 ones.
As discussed this week in Netconf 2023 in Paris, it is time
to upstream this for public use.
After this patch FQ can replace pfifo_fast, with the following
differences :
- FQ uses WRR instead of strict prio, to avoid starvation of
low priority packets.
- We make sure each band/prio tracks its own usage against sch->limit.
This was done to make sure flood of low priority packets would not
prevent AF4 packets to be queued. Contributed by Willem.
- priomap can be changed, if needed (default value are the ones
coming from pfifo_fast).
In this patch, we set default band weights so that :
- high prio (band=0) packets get 90% of the bandwidth
if they compete with low prio (band=2) packets.
- high prio packets get 75% of the bandwidth
if they compete with medium prio (band=1) packets.
Following patch in this series adds the possibility to tune
the per-band weights.
As we added many fields in 'struct fq_sched_data', we had
to make sure to have the first cache line read-mostly, and
avoid wasting precious cache lines.
More optimizations are possible but will be sent separately.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Dave Taht <dave.taht@gmail.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Diffstat (limited to 'net/sched/sch_fq.c')
-rw-r--r-- | net/sched/sch_fq.c | 204 |
1 files changed, 162 insertions, 42 deletions
diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c index 818ac786379d..081105801fa6 100644 --- a/net/sched/sch_fq.c +++ b/net/sched/sch_fq.c @@ -51,7 +51,8 @@ #include <net/tcp.h> struct fq_skb_cb { - u64 time_to_send; + u64 time_to_send; + u8 band; }; static inline struct fq_skb_cb *fq_skb_cb(struct sk_buff *skb) @@ -84,32 +85,28 @@ struct fq_flow { u32 socket_hash; /* sk_hash */ int qlen; /* number of packets in flow queue */ -/* Second cache line, used in fq_dequeue() */ +/* Second cache line */ int credit; - /* 32bit hole on 64bit arches */ - + int band; struct fq_flow *next; /* next pointer in RR lists */ struct rb_node rate_node; /* anchor in q->delayed tree */ u64 time_next_packet; -} ____cacheline_aligned_in_smp; +}; struct fq_flow_head { struct fq_flow *first; struct fq_flow *last; }; -struct fq_sched_data { +struct fq_perband_flows { struct fq_flow_head new_flows; - struct fq_flow_head old_flows; + int credit; + int quantum; /* based on band nr : 576KB, 192KB, 64KB */ +}; - struct rb_root delayed; /* for rate limited flows */ - u64 time_next_delayed_flow; - unsigned long unthrottle_latency_ns; - - struct fq_flow internal; /* for non classified or high prio packets */ - +struct fq_sched_data { /* Read mostly cache line */ u32 quantum; @@ -125,10 +122,21 @@ struct fq_sched_data { u8 rate_enable; u8 fq_trees_log; u8 horizon_drop; + u8 prio2band[(TC_PRIO_MAX + 1) >> 2]; u32 timer_slack; /* hrtimer slack in ns */ /* Read/Write fields. */ + unsigned int band_nr; /* band being serviced in fq_dequeue() */ + + struct fq_perband_flows band_flows[FQ_BANDS]; + + struct fq_flow internal; /* fastpath queue. */ + struct rb_root delayed; /* for rate limited flows */ + u64 time_next_delayed_flow; + unsigned long unthrottle_latency_ns; + + u32 band_pkt_count[FQ_BANDS]; u32 flows; u32 inactive_flows; /* Flows with no packet to send. */ u32 throttled_flows; @@ -139,7 +147,7 @@ struct fq_sched_data { /* Seldom used fields. */ - u64 stat_internal_packets; /* aka highprio */ + u64 stat_band_drops[FQ_BANDS]; u64 stat_ce_mark; u64 stat_horizon_drops; u64 stat_horizon_caps; @@ -148,6 +156,12 @@ struct fq_sched_data { u64 stat_allocation_errors; }; +/* return the i-th 2-bit value ("crumb") */ +static u8 fq_prio2band(const u8 *prio2band, unsigned int prio) +{ + return (prio2band[prio / 4] >> (2 * (prio & 0x3))) & 0x3; +} + /* * f->tail and f->age share the same location. * We can use the low order bit to differentiate if this location points @@ -172,8 +186,19 @@ static bool fq_flow_is_throttled(const struct fq_flow *f) return f->next == &throttled; } -static void fq_flow_add_tail(struct fq_flow_head *head, struct fq_flow *flow) +enum new_flow { + NEW_FLOW, + OLD_FLOW +}; + +static void fq_flow_add_tail(struct fq_sched_data *q, struct fq_flow *flow, + enum new_flow list_sel) { + struct fq_perband_flows *pband = &q->band_flows[flow->band]; + struct fq_flow_head *head = (list_sel == NEW_FLOW) ? + &pband->new_flows : + &pband->old_flows; + if (head->first) head->last->next = flow; else @@ -186,7 +211,7 @@ static void fq_flow_unset_throttled(struct fq_sched_data *q, struct fq_flow *f) { rb_erase(&f->rate_node, &q->delayed); q->throttled_flows--; - fq_flow_add_tail(&q->old_flows, f); + fq_flow_add_tail(q, f, OLD_FLOW); } static void fq_flow_set_throttled(struct fq_sched_data *q, struct fq_flow *f) @@ -326,11 +351,6 @@ static struct fq_flow *fq_classify(struct Qdisc *sch, struct sk_buff *skb, struct rb_root *root; struct fq_flow *f; - /* warning: no starvation prevention... */ - if (unlikely((skb->priority & TC_PRIO_MAX) == TC_PRIO_CONTROL)) { - q->stat_internal_packets++; /* highprio packet */ - return &q->internal; - } /* SYNACK messages are attached to a TCP_NEW_SYN_RECV request socket * or a listener (SYNCOOKIE mode) * 1) request sockets are not full blown, @@ -509,9 +529,13 @@ static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct fq_sched_data *q = qdisc_priv(sch); struct fq_flow *f; u64 now; + u8 band; - if (unlikely(sch->q.qlen >= sch->limit)) + band = fq_prio2band(q->prio2band, skb->priority & TC_PRIO_MAX); + if (unlikely(q->band_pkt_count[band] >= sch->limit)) { + q->stat_band_drops[band]++; return qdisc_drop(skb, sch, to_free); + } now = ktime_get_ns(); if (!skb->tstamp) { @@ -538,11 +562,14 @@ static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch, } if (fq_flow_is_detached(f)) { - fq_flow_add_tail(&q->new_flows, f); + fq_flow_add_tail(q, f, NEW_FLOW); if (time_after(jiffies, f->age + q->flow_refill_delay)) f->credit = max_t(u32, f->credit, q->quantum); } + f->band = band; + q->band_pkt_count[band]++; + fq_skb_cb(skb)->band = band; if (f->qlen == 0) q->inactive_flows--; } @@ -584,13 +611,26 @@ static void fq_check_throttled(struct fq_sched_data *q, u64 now) } } +static struct fq_flow_head *fq_pband_head_select(struct fq_perband_flows *pband) +{ + if (pband->credit <= 0) + return NULL; + + if (pband->new_flows.first) + return &pband->new_flows; + + return pband->old_flows.first ? &pband->old_flows : NULL; +} + static struct sk_buff *fq_dequeue(struct Qdisc *sch) { struct fq_sched_data *q = qdisc_priv(sch); + struct fq_perband_flows *pband; struct fq_flow_head *head; struct sk_buff *skb; struct fq_flow *f; unsigned long rate; + int retry; u32 plen; u64 now; @@ -606,24 +646,31 @@ static struct sk_buff *fq_dequeue(struct Qdisc *sch) now = ktime_get_ns(); fq_check_throttled(q, now); + retry = 0; + pband = &q->band_flows[q->band_nr]; begin: - head = &q->new_flows; - if (!head->first) { - head = &q->old_flows; - if (!head->first) { - if (q->time_next_delayed_flow != ~0ULL) - qdisc_watchdog_schedule_range_ns(&q->watchdog, + head = fq_pband_head_select(pband); + if (!head) { + while (++retry < FQ_BANDS) { + if (++q->band_nr == FQ_BANDS) + q->band_nr = 0; + pband = &q->band_flows[q->band_nr]; + pband->credit = min(pband->credit + pband->quantum, + pband->quantum); + goto begin; + } + if (q->time_next_delayed_flow != ~0ULL) + qdisc_watchdog_schedule_range_ns(&q->watchdog, q->time_next_delayed_flow, q->timer_slack); - return NULL; - } + return NULL; } f = head->first; - + retry = 0; if (f->credit <= 0) { f->credit += q->quantum; head->first = f->next; - fq_flow_add_tail(&q->old_flows, f); + fq_flow_add_tail(q, f, OLD_FLOW); goto begin; } @@ -645,12 +692,13 @@ begin: } if (--f->qlen == 0) q->inactive_flows++; + q->band_pkt_count[fq_skb_cb(skb)->band]--; fq_dequeue_skb(sch, f, skb); } else { head->first = f->next; /* force a pass through old_flows to prevent starvation */ - if ((head == &q->new_flows) && q->old_flows.first) { - fq_flow_add_tail(&q->old_flows, f); + if (head == &pband->new_flows) { + fq_flow_add_tail(q, f, OLD_FLOW); } else { fq_flow_set_detached(f); } @@ -658,6 +706,7 @@ begin: } plen = qdisc_pkt_len(skb); f->credit -= plen; + pband->credit -= plen; if (!q->rate_enable) goto out; @@ -749,8 +798,10 @@ static void fq_reset(struct Qdisc *sch) kmem_cache_free(fq_flow_cachep, f); } } - q->new_flows.first = NULL; - q->old_flows.first = NULL; + for (idx = 0; idx < FQ_BANDS; idx++) { + q->band_flows[idx].new_flows.first = NULL; + q->band_flows[idx].old_flows.first = NULL; + } q->delayed = RB_ROOT; q->flows = 0; q->inactive_flows = 0; @@ -864,8 +915,54 @@ static const struct nla_policy fq_policy[TCA_FQ_MAX + 1] = { [TCA_FQ_TIMER_SLACK] = { .type = NLA_U32 }, [TCA_FQ_HORIZON] = { .type = NLA_U32 }, [TCA_FQ_HORIZON_DROP] = { .type = NLA_U8 }, + [TCA_FQ_PRIOMAP] = { + .type = NLA_BINARY, + .len = sizeof(struct tc_prio_qopt), + }, }; +/* compress a u8 array with all elems <= 3 to an array of 2-bit fields */ +static void fq_prio2band_compress_crumb(const u8 *in, u8 *out) +{ + const int num_elems = TC_PRIO_MAX + 1; + int i; + + memset(out, 0, num_elems / 4); + for (i = 0; i < num_elems; i++) + out[i / 4] |= in[i] << (2 * (i & 0x3)); +} + +static void fq_prio2band_decompress_crumb(const u8 *in, u8 *out) +{ + const int num_elems = TC_PRIO_MAX + 1; + int i; + + for (i = 0; i < num_elems; i++) + out[i] = fq_prio2band(in, i); +} + +static int fq_load_priomap(struct fq_sched_data *q, + const struct nlattr *attr, + struct netlink_ext_ack *extack) +{ + const struct tc_prio_qopt *map = nla_data(attr); + int i; + + if (map->bands != FQ_BANDS) { + NL_SET_ERR_MSG_MOD(extack, "FQ only supports 3 bands"); + return -EINVAL; + } + for (i = 0; i < TC_PRIO_MAX + 1; i++) { + if (map->priomap[i] >= FQ_BANDS) { + NL_SET_ERR_MSG_FMT_MOD(extack, "FQ priomap field %d maps to a too high band %d", + i, map->priomap[i]); + return -EINVAL; + } + } + fq_prio2band_compress_crumb(map->priomap, q->prio2band); + return 0; +} + static int fq_change(struct Qdisc *sch, struct nlattr *opt, struct netlink_ext_ack *extack) { @@ -940,6 +1037,9 @@ static int fq_change(struct Qdisc *sch, struct nlattr *opt, q->flow_refill_delay = usecs_to_jiffies(usecs_delay); } + if (!err && tb[TCA_FQ_PRIOMAP]) + err = fq_load_priomap(q, tb[TCA_FQ_PRIOMAP], extack); + if (tb[TCA_FQ_ORPHAN_MASK]) q->orphan_mask = nla_get_u32(tb[TCA_FQ_ORPHAN_MASK]); @@ -991,7 +1091,7 @@ static int fq_init(struct Qdisc *sch, struct nlattr *opt, struct netlink_ext_ack *extack) { struct fq_sched_data *q = qdisc_priv(sch); - int err; + int i, err; sch->limit = 10000; q->flow_plimit = 100; @@ -1001,8 +1101,13 @@ static int fq_init(struct Qdisc *sch, struct nlattr *opt, q->flow_max_rate = ~0UL; q->time_next_delayed_flow = ~0ULL; q->rate_enable = 1; - q->new_flows.first = NULL; - q->old_flows.first = NULL; + for (i = 0; i < FQ_BANDS; i++) { + q->band_flows[i].new_flows.first = NULL; + q->band_flows[i].old_flows.first = NULL; + } + q->band_flows[0].quantum = 9 << 16; + q->band_flows[1].quantum = 3 << 16; + q->band_flows[2].quantum = 1 << 16; q->delayed = RB_ROOT; q->fq_root = NULL; q->fq_trees_log = ilog2(1024); @@ -1017,6 +1122,7 @@ static int fq_init(struct Qdisc *sch, struct nlattr *opt, /* Default ce_threshold of 4294 seconds */ q->ce_threshold = (u64)NSEC_PER_USEC * ~0U; + fq_prio2band_compress_crumb(sch_default_prio2band, q->prio2band); qdisc_watchdog_init_clockid(&q->watchdog, sch, CLOCK_MONOTONIC); if (opt) @@ -1031,6 +1137,9 @@ static int fq_dump(struct Qdisc *sch, struct sk_buff *skb) { struct fq_sched_data *q = qdisc_priv(sch); u64 ce_threshold = q->ce_threshold; + struct tc_prio_qopt prio = { + .bands = FQ_BANDS, + }; u64 horizon = q->horizon; struct nlattr *opts; @@ -1062,6 +1171,10 @@ static int fq_dump(struct Qdisc *sch, struct sk_buff *skb) nla_put_u8(skb, TCA_FQ_HORIZON_DROP, q->horizon_drop)) goto nla_put_failure; + fq_prio2band_decompress_crumb(q->prio2band, prio.priomap); + if (nla_put(skb, TCA_FQ_PRIOMAP, sizeof(prio), &prio)) + goto nla_put_failure; + return nla_nest_end(skb, opts); nla_put_failure: @@ -1072,11 +1185,14 @@ static int fq_dump_stats(struct Qdisc *sch, struct gnet_dump *d) { struct fq_sched_data *q = qdisc_priv(sch); struct tc_fq_qd_stats st; + int i; + + st.pad = 0; sch_tree_lock(sch); st.gc_flows = q->stat_gc_flows; - st.highprio_packets = q->stat_internal_packets; + st.highprio_packets = 0; st.fastpath_packets = q->internal.stat_fastpath_packets; st.tcp_retrans = 0; st.throttled = q->stat_throttled; @@ -1093,6 +1209,10 @@ static int fq_dump_stats(struct Qdisc *sch, struct gnet_dump *d) st.ce_mark = q->stat_ce_mark; st.horizon_drops = q->stat_horizon_drops; st.horizon_caps = q->stat_horizon_caps; + for (i = 0; i < FQ_BANDS; i++) { + st.band_drops[i] = q->stat_band_drops[i]; + st.band_pkt_count[i] = q->band_pkt_count[i]; + } sch_tree_unlock(sch); return gnet_stats_copy_app(d, &st, sizeof(st)); @@ -1120,7 +1240,7 @@ static int __init fq_module_init(void) fq_flow_cachep = kmem_cache_create("fq_flow_cache", sizeof(struct fq_flow), - 0, 0, NULL); + 0, SLAB_HWCACHE_ALIGN, NULL); if (!fq_flow_cachep) return -ENOMEM; |