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218 lines
6.8 KiB
Diff
218 lines
6.8 KiB
Diff
From 712639929912c5eefb09facccb48d55b3f72c9f8 Mon Sep 17 00:00:00 2001
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From: George Amanakis <gamanakis@gmail.com>
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Date: Fri, 1 Mar 2019 16:04:05 +0100
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Subject: [PATCH] sch_cake: Make the dual modes fairer
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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CAKE host fairness does not work well with TCP flows in dual-srchost and
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dual-dsthost setup. The reason is that ACKs generated by TCP flows are
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classified as sparse flows, and affect flow isolation from other hosts. Fix
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this by calculating host_load based only on the bulk flows a host
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generates. In a hash collision the host_bulk_flow_count values must be
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decremented on the old hosts and incremented on the new ones *if* the queue
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is in the bulk set.
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Reported-by: Pete Heist <peteheist@gmail.com>
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Signed-off-by: George Amanakis <gamanakis@gmail.com>
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Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
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---
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net/sched/sch_cake.c | 92 ++++++++++++++++++++++++++++++--------------
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1 file changed, 63 insertions(+), 29 deletions(-)
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--- a/net/sched/sch_cake.c
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+++ b/net/sched/sch_cake.c
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@@ -138,8 +138,8 @@ struct cake_flow {
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struct cake_host {
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u32 srchost_tag;
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u32 dsthost_tag;
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- u16 srchost_refcnt;
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- u16 dsthost_refcnt;
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+ u16 srchost_bulk_flow_count;
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+ u16 dsthost_bulk_flow_count;
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};
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struct cake_heap_entry {
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@@ -746,8 +746,10 @@ skip_hash:
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* queue, accept the collision, update the host tags.
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*/
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q->way_collisions++;
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- q->hosts[q->flows[reduced_hash].srchost].srchost_refcnt--;
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- q->hosts[q->flows[reduced_hash].dsthost].dsthost_refcnt--;
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+ if (q->flows[outer_hash + k].set == CAKE_SET_BULK) {
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+ q->hosts[q->flows[reduced_hash].srchost].srchost_bulk_flow_count--;
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+ q->hosts[q->flows[reduced_hash].dsthost].dsthost_bulk_flow_count--;
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+ }
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allocate_src = cake_dsrc(flow_mode);
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allocate_dst = cake_ddst(flow_mode);
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found:
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@@ -767,13 +769,14 @@ found:
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}
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for (i = 0; i < CAKE_SET_WAYS;
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i++, k = (k + 1) % CAKE_SET_WAYS) {
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- if (!q->hosts[outer_hash + k].srchost_refcnt)
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+ if (!q->hosts[outer_hash + k].srchost_bulk_flow_count)
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break;
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}
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q->hosts[outer_hash + k].srchost_tag = srchost_hash;
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found_src:
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srchost_idx = outer_hash + k;
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- q->hosts[srchost_idx].srchost_refcnt++;
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+ if (q->flows[reduced_hash].set == CAKE_SET_BULK)
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+ q->hosts[srchost_idx].srchost_bulk_flow_count++;
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q->flows[reduced_hash].srchost = srchost_idx;
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}
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@@ -789,13 +792,14 @@ found_src:
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}
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for (i = 0; i < CAKE_SET_WAYS;
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i++, k = (k + 1) % CAKE_SET_WAYS) {
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- if (!q->hosts[outer_hash + k].dsthost_refcnt)
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+ if (!q->hosts[outer_hash + k].dsthost_bulk_flow_count)
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break;
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}
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q->hosts[outer_hash + k].dsthost_tag = dsthost_hash;
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found_dst:
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dsthost_idx = outer_hash + k;
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- q->hosts[dsthost_idx].dsthost_refcnt++;
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+ if (q->flows[reduced_hash].set == CAKE_SET_BULK)
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+ q->hosts[dsthost_idx].dsthost_bulk_flow_count++;
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q->flows[reduced_hash].dsthost = dsthost_idx;
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}
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}
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@@ -1793,20 +1797,30 @@ static s32 cake_enqueue(struct sk_buff *
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b->sparse_flow_count++;
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if (cake_dsrc(q->flow_mode))
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- host_load = max(host_load, srchost->srchost_refcnt);
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+ host_load = max(host_load, srchost->srchost_bulk_flow_count);
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if (cake_ddst(q->flow_mode))
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- host_load = max(host_load, dsthost->dsthost_refcnt);
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+ host_load = max(host_load, dsthost->dsthost_bulk_flow_count);
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flow->deficit = (b->flow_quantum *
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quantum_div[host_load]) >> 16;
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} else if (flow->set == CAKE_SET_SPARSE_WAIT) {
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+ struct cake_host *srchost = &b->hosts[flow->srchost];
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+ struct cake_host *dsthost = &b->hosts[flow->dsthost];
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+
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/* this flow was empty, accounted as a sparse flow, but actually
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* in the bulk rotation.
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*/
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flow->set = CAKE_SET_BULK;
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b->sparse_flow_count--;
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b->bulk_flow_count++;
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+
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+ if (cake_dsrc(q->flow_mode))
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+ srchost->srchost_bulk_flow_count++;
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+
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+ if (cake_ddst(q->flow_mode))
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+ dsthost->dsthost_bulk_flow_count++;
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+
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}
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if (q->buffer_used > q->buffer_max_used)
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@@ -1974,23 +1988,8 @@ retry:
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dsthost = &b->hosts[flow->dsthost];
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host_load = 1;
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- if (cake_dsrc(q->flow_mode))
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- host_load = max(host_load, srchost->srchost_refcnt);
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-
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- if (cake_ddst(q->flow_mode))
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- host_load = max(host_load, dsthost->dsthost_refcnt);
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-
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- WARN_ON(host_load > CAKE_QUEUES);
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-
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/* flow isolation (DRR++) */
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if (flow->deficit <= 0) {
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- /* The shifted prandom_u32() is a way to apply dithering to
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- * avoid accumulating roundoff errors
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- */
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- flow->deficit += (b->flow_quantum * quantum_div[host_load] +
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- (prandom_u32() >> 16)) >> 16;
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- list_move_tail(&flow->flowchain, &b->old_flows);
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-
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/* Keep all flows with deficits out of the sparse and decaying
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* rotations. No non-empty flow can go into the decaying
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* rotation, so they can't get deficits
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@@ -1999,6 +1998,13 @@ retry:
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if (flow->head) {
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b->sparse_flow_count--;
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b->bulk_flow_count++;
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+
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+ if (cake_dsrc(q->flow_mode))
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+ srchost->srchost_bulk_flow_count++;
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+
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+ if (cake_ddst(q->flow_mode))
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+ dsthost->dsthost_bulk_flow_count++;
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+
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flow->set = CAKE_SET_BULK;
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} else {
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/* we've moved it to the bulk rotation for
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@@ -2008,6 +2014,22 @@ retry:
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flow->set = CAKE_SET_SPARSE_WAIT;
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}
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}
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+
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+ if (cake_dsrc(q->flow_mode))
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+ host_load = max(host_load, srchost->srchost_bulk_flow_count);
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+
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+ if (cake_ddst(q->flow_mode))
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+ host_load = max(host_load, dsthost->dsthost_bulk_flow_count);
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+
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+ WARN_ON(host_load > CAKE_QUEUES);
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+
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+ /* The shifted prandom_u32() is a way to apply dithering to
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+ * avoid accumulating roundoff errors
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+ */
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+ flow->deficit += (b->flow_quantum * quantum_div[host_load] +
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+ (prandom_u32() >> 16)) >> 16;
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+ list_move_tail(&flow->flowchain, &b->old_flows);
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+
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goto retry;
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}
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@@ -2028,6 +2050,13 @@ retry:
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&b->decaying_flows);
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if (flow->set == CAKE_SET_BULK) {
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b->bulk_flow_count--;
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+
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+ if (cake_dsrc(q->flow_mode))
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+ srchost->srchost_bulk_flow_count--;
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+
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+ if (cake_ddst(q->flow_mode))
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+ dsthost->dsthost_bulk_flow_count--;
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+
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b->decaying_flow_count++;
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} else if (flow->set == CAKE_SET_SPARSE ||
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flow->set == CAKE_SET_SPARSE_WAIT) {
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@@ -2041,14 +2070,19 @@ retry:
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if (flow->set == CAKE_SET_SPARSE ||
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flow->set == CAKE_SET_SPARSE_WAIT)
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b->sparse_flow_count--;
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- else if (flow->set == CAKE_SET_BULK)
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+ else if (flow->set == CAKE_SET_BULK) {
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b->bulk_flow_count--;
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- else
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+
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+ if (cake_dsrc(q->flow_mode))
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+ srchost->srchost_bulk_flow_count--;
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+
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+ if (cake_ddst(q->flow_mode))
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+ dsthost->dsthost_bulk_flow_count--;
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+
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+ } else
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b->decaying_flow_count--;
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flow->set = CAKE_SET_NONE;
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- srchost->srchost_refcnt--;
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- dsthost->dsthost_refcnt--;
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}
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goto begin;
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}
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