From 712639929912c5eefb09facccb48d55b3f72c9f8 Mon Sep 17 00:00:00 2001 From: George Amanakis Date: Fri, 1 Mar 2019 16:04:05 +0100 Subject: sch_cake: Make the dual modes fairer MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit CAKE host fairness does not work well with TCP flows in dual-srchost and dual-dsthost setup. The reason is that ACKs generated by TCP flows are classified as sparse flows, and affect flow isolation from other hosts. Fix this by calculating host_load based only on the bulk flows a host generates. In a hash collision the host_bulk_flow_count values must be decremented on the old hosts and incremented on the new ones *if* the queue is in the bulk set. Reported-by: Pete Heist Signed-off-by: George Amanakis Signed-off-by: Toke Høiland-Jørgensen Signed-off-by: David S. Miller --- net/sched/sch_cake.c | 92 +++++++++++++++++++++++++++++++++++----------------- 1 file changed, 63 insertions(+), 29 deletions(-) (limited to 'net/sched/sch_cake.c') diff --git a/net/sched/sch_cake.c b/net/sched/sch_cake.c index 73940293700d..4d688b3b471b 100644 --- a/net/sched/sch_cake.c +++ b/net/sched/sch_cake.c @@ -138,8 +138,8 @@ struct cake_flow { struct cake_host { u32 srchost_tag; u32 dsthost_tag; - u16 srchost_refcnt; - u16 dsthost_refcnt; + u16 srchost_bulk_flow_count; + u16 dsthost_bulk_flow_count; }; struct cake_heap_entry { @@ -746,8 +746,10 @@ skip_hash: * queue, accept the collision, update the host tags. */ q->way_collisions++; - q->hosts[q->flows[reduced_hash].srchost].srchost_refcnt--; - q->hosts[q->flows[reduced_hash].dsthost].dsthost_refcnt--; + if (q->flows[outer_hash + k].set == CAKE_SET_BULK) { + q->hosts[q->flows[reduced_hash].srchost].srchost_bulk_flow_count--; + q->hosts[q->flows[reduced_hash].dsthost].dsthost_bulk_flow_count--; + } allocate_src = cake_dsrc(flow_mode); allocate_dst = cake_ddst(flow_mode); found: @@ -767,13 +769,14 @@ found: } for (i = 0; i < CAKE_SET_WAYS; i++, k = (k + 1) % CAKE_SET_WAYS) { - if (!q->hosts[outer_hash + k].srchost_refcnt) + if (!q->hosts[outer_hash + k].srchost_bulk_flow_count) break; } q->hosts[outer_hash + k].srchost_tag = srchost_hash; found_src: srchost_idx = outer_hash + k; - q->hosts[srchost_idx].srchost_refcnt++; + if (q->flows[reduced_hash].set == CAKE_SET_BULK) + q->hosts[srchost_idx].srchost_bulk_flow_count++; q->flows[reduced_hash].srchost = srchost_idx; } @@ -789,13 +792,14 @@ found_src: } for (i = 0; i < CAKE_SET_WAYS; i++, k = (k + 1) % CAKE_SET_WAYS) { - if (!q->hosts[outer_hash + k].dsthost_refcnt) + if (!q->hosts[outer_hash + k].dsthost_bulk_flow_count) break; } q->hosts[outer_hash + k].dsthost_tag = dsthost_hash; found_dst: dsthost_idx = outer_hash + k; - q->hosts[dsthost_idx].dsthost_refcnt++; + if (q->flows[reduced_hash].set == CAKE_SET_BULK) + q->hosts[dsthost_idx].dsthost_bulk_flow_count++; q->flows[reduced_hash].dsthost = dsthost_idx; } } @@ -1794,20 +1798,30 @@ static s32 cake_enqueue(struct sk_buff *skb, struct Qdisc *sch, b->sparse_flow_count++; if (cake_dsrc(q->flow_mode)) - host_load = max(host_load, srchost->srchost_refcnt); + host_load = max(host_load, srchost->srchost_bulk_flow_count); if (cake_ddst(q->flow_mode)) - host_load = max(host_load, dsthost->dsthost_refcnt); + host_load = max(host_load, dsthost->dsthost_bulk_flow_count); flow->deficit = (b->flow_quantum * quantum_div[host_load]) >> 16; } else if (flow->set == CAKE_SET_SPARSE_WAIT) { + struct cake_host *srchost = &b->hosts[flow->srchost]; + struct cake_host *dsthost = &b->hosts[flow->dsthost]; + /* this flow was empty, accounted as a sparse flow, but actually * in the bulk rotation. */ flow->set = CAKE_SET_BULK; b->sparse_flow_count--; b->bulk_flow_count++; + + if (cake_dsrc(q->flow_mode)) + srchost->srchost_bulk_flow_count++; + + if (cake_ddst(q->flow_mode)) + dsthost->dsthost_bulk_flow_count++; + } if (q->buffer_used > q->buffer_max_used) @@ -1975,23 +1989,8 @@ retry: dsthost = &b->hosts[flow->dsthost]; host_load = 1; - if (cake_dsrc(q->flow_mode)) - host_load = max(host_load, srchost->srchost_refcnt); - - if (cake_ddst(q->flow_mode)) - host_load = max(host_load, dsthost->dsthost_refcnt); - - WARN_ON(host_load > CAKE_QUEUES); - /* flow isolation (DRR++) */ if (flow->deficit <= 0) { - /* The shifted prandom_u32() is a way to apply dithering to - * avoid accumulating roundoff errors - */ - flow->deficit += (b->flow_quantum * quantum_div[host_load] + - (prandom_u32() >> 16)) >> 16; - list_move_tail(&flow->flowchain, &b->old_flows); - /* Keep all flows with deficits out of the sparse and decaying * rotations. No non-empty flow can go into the decaying * rotation, so they can't get deficits @@ -2000,6 +1999,13 @@ retry: if (flow->head) { b->sparse_flow_count--; b->bulk_flow_count++; + + if (cake_dsrc(q->flow_mode)) + srchost->srchost_bulk_flow_count++; + + if (cake_ddst(q->flow_mode)) + dsthost->dsthost_bulk_flow_count++; + flow->set = CAKE_SET_BULK; } else { /* we've moved it to the bulk rotation for @@ -2009,6 +2015,22 @@ retry: flow->set = CAKE_SET_SPARSE_WAIT; } } + + if (cake_dsrc(q->flow_mode)) + host_load = max(host_load, srchost->srchost_bulk_flow_count); + + if (cake_ddst(q->flow_mode)) + host_load = max(host_load, dsthost->dsthost_bulk_flow_count); + + WARN_ON(host_load > CAKE_QUEUES); + + /* The shifted prandom_u32() is a way to apply dithering to + * avoid accumulating roundoff errors + */ + flow->deficit += (b->flow_quantum * quantum_div[host_load] + + (prandom_u32() >> 16)) >> 16; + list_move_tail(&flow->flowchain, &b->old_flows); + goto retry; } @@ -2029,6 +2051,13 @@ retry: &b->decaying_flows); if (flow->set == CAKE_SET_BULK) { b->bulk_flow_count--; + + if (cake_dsrc(q->flow_mode)) + srchost->srchost_bulk_flow_count--; + + if (cake_ddst(q->flow_mode)) + dsthost->dsthost_bulk_flow_count--; + b->decaying_flow_count++; } else if (flow->set == CAKE_SET_SPARSE || flow->set == CAKE_SET_SPARSE_WAIT) { @@ -2042,14 +2071,19 @@ retry: if (flow->set == CAKE_SET_SPARSE || flow->set == CAKE_SET_SPARSE_WAIT) b->sparse_flow_count--; - else if (flow->set == CAKE_SET_BULK) + else if (flow->set == CAKE_SET_BULK) { b->bulk_flow_count--; - else + + if (cake_dsrc(q->flow_mode)) + srchost->srchost_bulk_flow_count--; + + if (cake_ddst(q->flow_mode)) + dsthost->dsthost_bulk_flow_count--; + + } else b->decaying_flow_count--; flow->set = CAKE_SET_NONE; - srchost->srchost_refcnt--; - dsthost->dsthost_refcnt--; } goto begin; } -- cgit v1.2.3-59-g8ed1b