From 37c0aead7902b1ddf1b668e1ab74c80b9a7fd183 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sat, 4 May 2019 16:48:54 -0700 Subject: [PATCH] net_sched: sch_fq: handle non connected flows FQ packet scheduler assumed that packets could be classified based on their owning socket. This means that if a UDP server uses one UDP socket to send packets to different destinations, packets all land in one FQ flow. This is unfair, since each TCP flow has a unique bucket, meaning that in case of pressure (fully utilised uplink), TCP flows have more share of the bandwidth. If we instead detect unconnected sockets, we can use a stochastic hash based on the 4-tuple hash. This also means a QUIC server using one UDP socket will properly spread the outgoing packets to different buckets, and in-kernel pacing based on EDT model will no longer risk having big rb-tree on one flow. Note that UDP application might provide the skb->hash in an ancillary message at sendmsg() time to avoid the cost of a dissection in fq packet scheduler. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/sched/sch_fq.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c index ee138365ec45..26a94e5cd5df 100644 --- a/net/sched/sch_fq.c +++ b/net/sched/sch_fq.c @@ -270,6 +270,17 @@ static struct fq_flow *fq_classify(struct sk_buff *skb, struct fq_sched_data *q) */ sk = (struct sock *)((hash << 1) | 1UL); skb_orphan(skb); + } else if (sk->sk_state == TCP_CLOSE) { + unsigned long hash = skb_get_hash(skb) & q->orphan_mask; + /* + * Sockets in TCP_CLOSE are non connected. + * Typical use case is UDP sockets, they can send packets + * with sendto() to many different destinations. + * We probably could use a generic bit advertising + * non connected sockets, instead of sk_state == TCP_CLOSE, + * if we care enough. + */ + sk = (struct sock *)((hash << 1) | 1UL); } root = &q->fq_root[hash_ptr(sk, q->fq_trees_log)]; @@ -290,7 +301,7 @@ static struct fq_flow *fq_classify(struct sk_buff *skb, struct fq_sched_data *q) * It not, we need to refill credit with * initial quantum */ - if (unlikely(skb->sk && + if (unlikely(skb->sk == sk && f->socket_hash != sk->sk_hash)) { f->credit = q->initial_quantum; f->socket_hash = sk->sk_hash; @@ -315,7 +326,7 @@ static struct fq_flow *fq_classify(struct sk_buff *skb, struct fq_sched_data *q) fq_flow_set_detached(f); f->sk = sk; - if (skb->sk) + if (skb->sk == sk) f->socket_hash = sk->sk_hash; f->credit = q->initial_quantum; -- 2.30.2