netdev - [PATCH 1/3] fq.h: Port memory limit mechanism from fq

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Date:   Fri, 23 Sep 2016 21:59:09 +0200
From:   Toke Høiland-Jørgensen <toke@...e.dk>
To:     make-wifi-fast@...ts.bufferbloat.net,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Cc:     Toke Høiland-Jørgensen <toke@...e.dk>
Subject: [PATCH 1/3] fq.h: Port memory limit mechanism from fq_codel

The reusable fairness queueing implementation (fq.h) lacks the memory
usage limit that the fq_codel qdisc has. This means that small
devices (e.g. WiFi routers) can run out of memory when flooded with a
large number of packets. This ports the memory limit feature from
fq_codel to fq.h.

Signed-off-by: Toke Høiland-Jørgensen <toke@...e.dk>
---
 include/net/fq.h      | 3 +++
 include/net/fq_impl.h | 7 ++++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/include/net/fq.h b/include/net/fq.h
index 268b490..6d8521a 100644
--- a/include/net/fq.h
+++ b/include/net/fq.h
@@ -72,9 +72,12 @@ struct fq {
 	u32 flows_cnt;
 	u32 perturbation;
 	u32 limit;
+	u32 memory_limit;
+	u32 memory_usage;
 	u32 quantum;
 	u32 backlog;
 	u32 overlimit;
+	u32 overmemory;
 	u32 collisions;
 };
 
diff --git a/include/net/fq_impl.h b/include/net/fq_impl.h
index 163f3ed..4e6131c 100644
--- a/include/net/fq_impl.h
+++ b/include/net/fq_impl.h
@@ -29,6 +29,7 @@ static struct sk_buff *fq_flow_dequeue(struct fq *fq,
 	tin->backlog_packets--;
 	flow->backlog -= skb->len;
 	fq->backlog--;
+	fq->memory_usage -= skb->truesize;
 
 	if (flow->backlog == 0) {
 		list_del_init(&flow->backlogchain);
@@ -154,6 +155,7 @@ static void fq_tin_enqueue(struct fq *fq,
 	flow->backlog += skb->len;
 	tin->backlog_bytes += skb->len;
 	tin->backlog_packets++;
+	fq->memory_usage += skb->truesize;
 	fq->backlog++;
 
 	fq_recalc_backlog(fq, tin, flow);
@@ -166,7 +168,7 @@ static void fq_tin_enqueue(struct fq *fq,
 
 	__skb_queue_tail(&flow->queue, skb);
 
-	if (fq->backlog > fq->limit) {
+	if (fq->backlog > fq->limit || fq->memory_usage > fq->memory_limit) {
 		flow = list_first_entry_or_null(&fq->backlogs,
 						struct fq_flow,
 						backlogchain);
@@ -181,6 +183,8 @@ static void fq_tin_enqueue(struct fq *fq,
 
 		flow->tin->overlimit++;
 		fq->overlimit++;
+		if (fq->memory_usage > fq->memory_limit)
+			fq->overmemory++;
 	}
 }
 
@@ -251,6 +255,7 @@ static int fq_init(struct fq *fq, int flows_cnt)
 	fq->perturbation = prandom_u32();
 	fq->quantum = 300;
 	fq->limit = 8192;
+	fq->memory_limit = 16 << 20; /* 16 MBytes */
 
 	fq->flows = kcalloc(fq->flows_cnt, sizeof(fq->flows[0]), GFP_KERNEL);
 	if (!fq->flows)
-- 
2.9.3