ath10k: replenish HTT RX buffers in a tasklet
This starves FW RX ring buffer in case of
excessive RX. This prevents from CPU being
overwhelmed by RX indications/completions by
naturally forbiddin FW to submit more RX.
This fixes RX starvation on slow machines when
under heavy RX traffic.
kvalo: remove extra newline
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
diff --git a/drivers/net/wireless/ath/ath10k/htt_rx.c b/drivers/net/wireless/ath/ath10k/htt_rx.c
index c4637f1..90d4f74 100644
--- a/drivers/net/wireless/ath/ath10k/htt_rx.c
+++ b/drivers/net/wireless/ath/ath10k/htt_rx.c
@@ -182,10 +182,27 @@
static void ath10k_htt_rx_msdu_buff_replenish(struct ath10k_htt *htt)
{
- int ret, num_to_fill;
+ int ret, num_deficit, num_to_fill;
+ /* Refilling the whole RX ring buffer proves to be a bad idea. The
+ * reason is RX may take up significant amount of CPU cycles and starve
+ * other tasks, e.g. TX on an ethernet device while acting as a bridge
+ * with ath10k wlan interface. This ended up with very poor performance
+ * once CPU the host system was overwhelmed with RX on ath10k.
+ *
+ * By limiting the number of refills the replenishing occurs
+ * progressively. This in turns makes use of the fact tasklets are
+ * processed in FIFO order. This means actual RX processing can starve
+ * out refilling. If there's not enough buffers on RX ring FW will not
+ * report RX until it is refilled with enough buffers. This
+ * automatically balances load wrt to CPU power.
+ *
+ * This probably comes at a cost of lower maximum throughput but
+ * improves the avarage and stability. */
spin_lock_bh(&htt->rx_ring.lock);
- num_to_fill = htt->rx_ring.fill_level - htt->rx_ring.fill_cnt;
+ num_deficit = htt->rx_ring.fill_level - htt->rx_ring.fill_cnt;
+ num_to_fill = min(ATH10K_HTT_MAX_NUM_REFILL, num_deficit);
+ num_deficit -= num_to_fill;
ret = ath10k_htt_rx_ring_fill_n(htt, num_to_fill);
if (ret == -ENOMEM) {
/*
@@ -196,6 +213,8 @@
*/
mod_timer(&htt->rx_ring.refill_retry_timer, jiffies +
msecs_to_jiffies(HTT_RX_RING_REFILL_RETRY_MS));
+ } else if (num_deficit > 0) {
+ tasklet_schedule(&htt->rx_replenish_task);
}
spin_unlock_bh(&htt->rx_ring.lock);
}
@@ -217,6 +236,7 @@
int sw_rd_idx = htt->rx_ring.sw_rd_idx.msdu_payld;
del_timer_sync(&htt->rx_ring.refill_retry_timer);
+ tasklet_kill(&htt->rx_replenish_task);
while (sw_rd_idx != __le32_to_cpu(*(htt->rx_ring.alloc_idx.vaddr))) {
struct sk_buff *skb =
@@ -446,6 +466,12 @@
return msdu_chaining;
}
+static void ath10k_htt_rx_replenish_task(unsigned long ptr)
+{
+ struct ath10k_htt *htt = (struct ath10k_htt *)ptr;
+ ath10k_htt_rx_msdu_buff_replenish(htt);
+}
+
int ath10k_htt_rx_attach(struct ath10k_htt *htt)
{
dma_addr_t paddr;
@@ -506,6 +532,9 @@
if (__ath10k_htt_rx_ring_fill_n(htt, htt->rx_ring.fill_level))
goto err_fill_ring;
+ tasklet_init(&htt->rx_replenish_task, ath10k_htt_rx_replenish_task,
+ (unsigned long)htt);
+
ath10k_dbg(ATH10K_DBG_BOOT, "htt rx ring size %d fill_level %d\n",
htt->rx_ring.size, htt->rx_ring.fill_level);
return 0;
@@ -956,7 +985,7 @@
}
}
- ath10k_htt_rx_msdu_buff_replenish(htt);
+ tasklet_schedule(&htt->rx_replenish_task);
}
static void ath10k_htt_rx_frag_handler(struct ath10k_htt *htt,