diff options
Diffstat (limited to 'target/linux/generic/pending-4.4/032-fq_codel-add-batch-ability-to-fq_codel_drop.patch')
| -rw-r--r-- | target/linux/generic/pending-4.4/032-fq_codel-add-batch-ability-to-fq_codel_drop.patch | 189 |
1 files changed, 0 insertions, 189 deletions
diff --git a/target/linux/generic/pending-4.4/032-fq_codel-add-batch-ability-to-fq_codel_drop.patch b/target/linux/generic/pending-4.4/032-fq_codel-add-batch-ability-to-fq_codel_drop.patch deleted file mode 100644 index d1390348cb..0000000000 --- a/target/linux/generic/pending-4.4/032-fq_codel-add-batch-ability-to-fq_codel_drop.patch +++ /dev/null @@ -1,189 +0,0 @@ -From: Eric Dumazet <edumazet@google.com> -Date: Sun, 1 May 2016 16:47:26 -0700 -Subject: [PATCH] fq_codel: add batch ability to fq_codel_drop() - -In presence of inelastic flows and stress, we can call -fq_codel_drop() for every packet entering fq_codel qdisc. - -fq_codel_drop() is quite expensive, as it does a linear scan -of 4 KB of memory to find a fat flow. -Once found, it drops the oldest packet of this flow. - -Instead of dropping a single packet, try to drop 50% of the backlog -of this fat flow, with a configurable limit of 64 packets per round. - -TCA_FQ_CODEL_DROP_BATCH_SIZE is the new attribute to make this -limit configurable. - -With this strategy the 4 KB search is amortized to a single cache line -per drop [1], so fq_codel_drop() no longer appears at the top of kernel -profile in presence of few inelastic flows. - -[1] Assuming a 64byte cache line, and 1024 buckets - -Signed-off-by: Eric Dumazet <edumazet@google.com> -Reported-by: Dave Taht <dave.taht@gmail.com> -Cc: Jonathan Morton <chromatix99@gmail.com> -Acked-by: Jesper Dangaard Brouer <brouer@redhat.com> -Acked-by: Dave Taht -Signed-off-by: David S. Miller <davem@davemloft.net> ---- - ---- a/include/uapi/linux/pkt_sched.h -+++ b/include/uapi/linux/pkt_sched.h -@@ -711,6 +711,7 @@ enum { - TCA_FQ_CODEL_FLOWS, - TCA_FQ_CODEL_QUANTUM, - TCA_FQ_CODEL_CE_THRESHOLD, -+ TCA_FQ_CODEL_DROP_BATCH_SIZE, - __TCA_FQ_CODEL_MAX - }; - ---- a/net/sched/sch_fq_codel.c -+++ b/net/sched/sch_fq_codel.c -@@ -57,6 +57,7 @@ struct fq_codel_sched_data { - u32 flows_cnt; /* number of flows */ - u32 perturbation; /* hash perturbation */ - u32 quantum; /* psched_mtu(qdisc_dev(sch)); */ -+ u32 drop_batch_size; - struct codel_params cparams; - struct codel_stats cstats; - u32 drop_overlimit; -@@ -133,17 +134,20 @@ static inline void flow_queue_add(struct - skb->next = NULL; - } - --static unsigned int fq_codel_drop(struct Qdisc *sch) -+static unsigned int fq_codel_drop(struct Qdisc *sch, unsigned int max_packets) - { - struct fq_codel_sched_data *q = qdisc_priv(sch); - struct sk_buff *skb; - unsigned int maxbacklog = 0, idx = 0, i, len; - struct fq_codel_flow *flow; -+ unsigned int threshold; - -- /* Queue is full! Find the fat flow and drop packet from it. -+ /* Queue is full! Find the fat flow and drop packet(s) from it. - * This might sound expensive, but with 1024 flows, we scan - * 4KB of memory, and we dont need to handle a complex tree - * in fast path (packet queue/enqueue) with many cache misses. -+ * In stress mode, we'll try to drop 64 packets from the flow, -+ * amortizing this linear lookup to one cache line per drop. - */ - for (i = 0; i < q->flows_cnt; i++) { - if (q->backlogs[i] > maxbacklog) { -@@ -151,15 +155,24 @@ static unsigned int fq_codel_drop(struct - idx = i; - } - } -+ -+ /* Our goal is to drop half of this fat flow backlog */ -+ threshold = maxbacklog >> 1; -+ - flow = &q->flows[idx]; -- skb = dequeue_head(flow); -- len = qdisc_pkt_len(skb); -+ len = 0; -+ i = 0; -+ do { -+ skb = dequeue_head(flow); -+ len += qdisc_pkt_len(skb); -+ kfree_skb(skb); -+ } while (++i < max_packets && len < threshold); -+ -+ flow->dropped += i; - q->backlogs[idx] -= len; -- sch->q.qlen--; -- qdisc_qstats_drop(sch); -- qdisc_qstats_backlog_dec(sch, skb); -- kfree_skb(skb); -- flow->dropped++; -+ sch->qstats.drops += i; -+ sch->qstats.backlog -= len; -+ sch->q.qlen -= i; - return idx; - } - -@@ -168,14 +181,14 @@ static unsigned int fq_codel_qdisc_drop( - unsigned int prev_backlog; - - prev_backlog = sch->qstats.backlog; -- fq_codel_drop(sch); -+ fq_codel_drop(sch, 1U); - return prev_backlog - sch->qstats.backlog; - } - - static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch) - { - struct fq_codel_sched_data *q = qdisc_priv(sch); -- unsigned int idx, prev_backlog; -+ unsigned int idx, prev_backlog, prev_qlen; - struct fq_codel_flow *flow; - int uninitialized_var(ret); - -@@ -204,16 +217,22 @@ static int fq_codel_enqueue(struct sk_bu - return NET_XMIT_SUCCESS; - - prev_backlog = sch->qstats.backlog; -- q->drop_overlimit++; -- /* Return Congestion Notification only if we dropped a packet -- * from this flow. -+ prev_qlen = sch->q.qlen; -+ -+ /* fq_codel_drop() is quite expensive, as it performs a linear search -+ * in q->backlogs[] to find a fat flow. -+ * So instead of dropping a single packet, drop half of its backlog -+ * with a 64 packets limit to not add a too big cpu spike here. - */ -- if (fq_codel_drop(sch) == idx) -- return NET_XMIT_CN; -+ ret = fq_codel_drop(sch, q->drop_batch_size); -+ -+ q->drop_overlimit += prev_qlen - sch->q.qlen; - -- /* As we dropped a packet, better let upper stack know this */ -- qdisc_tree_reduce_backlog(sch, 1, prev_backlog - sch->qstats.backlog); -- return NET_XMIT_SUCCESS; -+ /* As we dropped packet(s), better let upper stack know this */ -+ qdisc_tree_reduce_backlog(sch, prev_qlen - sch->q.qlen, -+ prev_backlog - sch->qstats.backlog); -+ -+ return ret == idx ? NET_XMIT_CN : NET_XMIT_SUCCESS; - } - - /* This is the specific function called from codel_dequeue() -@@ -323,6 +342,7 @@ static const struct nla_policy fq_codel_ - [TCA_FQ_CODEL_FLOWS] = { .type = NLA_U32 }, - [TCA_FQ_CODEL_QUANTUM] = { .type = NLA_U32 }, - [TCA_FQ_CODEL_CE_THRESHOLD] = { .type = NLA_U32 }, -+ [TCA_FQ_CODEL_DROP_BATCH_SIZE] = { .type = NLA_U32 }, - }; - - static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt) -@@ -374,6 +394,9 @@ static int fq_codel_change(struct Qdisc - if (tb[TCA_FQ_CODEL_QUANTUM]) - q->quantum = max(256U, nla_get_u32(tb[TCA_FQ_CODEL_QUANTUM])); - -+ if (tb[TCA_FQ_CODEL_DROP_BATCH_SIZE]) -+ q->drop_batch_size = min(1U, nla_get_u32(tb[TCA_FQ_CODEL_DROP_BATCH_SIZE])); -+ - while (sch->q.qlen > sch->limit) { - struct sk_buff *skb = fq_codel_dequeue(sch); - -@@ -419,6 +442,7 @@ static int fq_codel_init(struct Qdisc *s - - sch->limit = 10*1024; - q->flows_cnt = 1024; -+ q->drop_batch_size = 64; - q->quantum = psched_mtu(qdisc_dev(sch)); - q->perturbation = prandom_u32(); - INIT_LIST_HEAD(&q->new_flows); -@@ -476,6 +500,8 @@ static int fq_codel_dump(struct Qdisc *s - q->cparams.ecn) || - nla_put_u32(skb, TCA_FQ_CODEL_QUANTUM, - q->quantum) || -+ nla_put_u32(skb, TCA_FQ_CODEL_DROP_BATCH_SIZE, -+ q->drop_batch_size) || - nla_put_u32(skb, TCA_FQ_CODEL_FLOWS, - q->flows_cnt)) - goto nla_put_failure; |