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-rw-r--r--target/linux/generic/backport-4.19/392-v5.1-sch_cake-Make-the-dual-modes-fairer.patch217
1 files changed, 217 insertions, 0 deletions
diff --git a/target/linux/generic/backport-4.19/392-v5.1-sch_cake-Make-the-dual-modes-fairer.patch b/target/linux/generic/backport-4.19/392-v5.1-sch_cake-Make-the-dual-modes-fairer.patch
new file mode 100644
index 0000000000..cd94600152
--- /dev/null
+++ b/target/linux/generic/backport-4.19/392-v5.1-sch_cake-Make-the-dual-modes-fairer.patch
@@ -0,0 +1,217 @@
+From 712639929912c5eefb09facccb48d55b3f72c9f8 Mon Sep 17 00:00:00 2001
+From: George Amanakis <gamanakis@gmail.com>
+Date: Fri, 1 Mar 2019 16:04:05 +0100
+Subject: [PATCH] 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 <peteheist@gmail.com>
+Signed-off-by: George Amanakis <gamanakis@gmail.com>
+Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
+---
+ net/sched/sch_cake.c | 92 ++++++++++++++++++++++++++++++--------------
+ 1 file changed, 63 insertions(+), 29 deletions(-)
+
+--- 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;
+ }
+ }
+@@ -1793,20 +1797,30 @@ static s32 cake_enqueue(struct sk_buff *
+ 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)
+@@ -1974,23 +1988,8 @@ 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
+@@ -1999,6 +1998,13 @@ 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
+@@ -2008,6 +2014,22 @@ 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;
+ }
+
+@@ -2028,6 +2050,13 @@ 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) {
+@@ -2041,14 +2070,19 @@ 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;
+ }