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Message-ID: <1423084303.31870.15.camel@edumazet-glaptop2.roam.corp.google.com>
Date: Wed, 04 Feb 2015 13:11:43 -0800
From: Eric Dumazet <eric.dumazet@...il.com>
To: Michal Kazior <michal.kazior@...to.com>
Cc: Neal Cardwell <ncardwell@...gle.com>,
linux-wireless <linux-wireless@...r.kernel.org>,
Network Development <netdev@...r.kernel.org>,
eyalpe@....mellanox.co.il
Subject: Re: Throughput regression with `tcp: refine TSO autosizing`
I do not see how a TSO patch could hurt a flow not using TSO/GSO.
This makes no sense.
ath10k tx completions being batched/deferred to a tasklet might increase
probability to hit this condition in tcp_wfree() :
/* If this softirq is serviced by ksoftirqd, we are likely under stress.
* Wait until our queues (qdisc + devices) are drained.
* This gives :
* - less callbacks to tcp_write_xmit(), reducing stress (batches)
* - chance for incoming ACK (processed by another cpu maybe)
* to migrate this flow (skb->ooo_okay will be eventually set)
*/
if (wmem >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
goto out;
Meaning tcp stack waits all skbs left qdisc/NIC queues before queuing
additional packets.
I would try to call skb_orphan() in ath10k if you really want to keep
these batches.
I have hard time to understand why tx completed packets go through
ath10k_htc_rx_completion_handler().. anyway...
Most conservative patch would be :
diff --git a/drivers/net/wireless/ath/ath10k/htt_rx.c b/drivers/net/wireless/ath/ath10k/htt_rx.c
index 9c782a42665e1aaf43bfbca441631ee58da50c09..6a36317d6bb0447202dee15528130bd5e21248c4 100644
--- a/drivers/net/wireless/ath/ath10k/htt_rx.c
+++ b/drivers/net/wireless/ath/ath10k/htt_rx.c
@@ -1642,6 +1642,7 @@ void ath10k_htt_t2h_msg_handler(struct ath10k *ar, struct sk_buff *skb)
break;
}
case HTT_T2H_MSG_TYPE_TX_COMPL_IND:
+ skb_orphan(skb);
spin_lock_bh(&htt->tx_lock);
__skb_queue_tail(&htt->tx_compl_q, skb);
spin_unlock_bh(&htt->tx_lock);
--
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