netdev - [PATCH 3/3] mac80211: Set lower memory limit for non-VHT devices

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Message-Id: <20160923195911.4572-4-toke@toke.dk>
Date:   Fri, 23 Sep 2016 21:59:11 +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 3/3] mac80211: Set lower memory limit for non-VHT devices

Small devices can run out of memory from queueing too many packets. If
VHT is not supported by the PHY, having more than 4 MBytes of total
queue in the TXQ intermediate queues is not needed, and so we can safely
limit the memory usage in these cases and avoid OOM.

Signed-off-by: Toke Høiland-Jørgensen <toke@...e.dk>
---
 net/mac80211/tx.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 1ff08be..82f41fc 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1434,6 +1434,8 @@ int ieee80211_txq_setup_flows(struct ieee80211_local *local)
 	struct fq *fq = &local->fq;
 	int ret;
 	int i;
+	bool supp_vht = false;
+	enum nl80211_band band;
 
 	if (!local->ops->wake_tx_queue)
 		return 0;
@@ -1442,6 +1444,22 @@ int ieee80211_txq_setup_flows(struct ieee80211_local *local)
 	if (ret)
 		return ret;
 
+	/*
+	 * If the hardware doesn't support VHT, it is safe to limit the maximum
+	 * queue size. 4 Mbytes is 64 max-size aggregates in 802.11n.
+	 */
+	for (band = 0; band < NUM_NL80211_BANDS; band++) {
+		struct ieee80211_supported_band *sband;
+
+		sband = local->hw.wiphy->bands[band];
+		if (!sband)
+			continue;
+
+		supp_vht = supp_vht || sband->vht_cap.vht_supported;
+	}
+	if (!supp_vht)
+		fq->memory_limit = 4 << 20; /* 4 Mbytes */
+
 	codel_params_init(&local->cparams);
 	local->cparams.interval = MS2TIME(100);
 	local->cparams.target = MS2TIME(20);
-- 
2.9.3