From: Kalle Valo <kvalo@codeaurora.org>
To: Erik Stromdahl <erik.stromdahl@gmail.com>
Cc: kvalo@qca.qualcomm.com, linux-wireless@vger.kernel.org,
ath10k@lists.infradead.org, yiboz@codeaurora.org,
Erik Stromdahl <erik.stromdahl@gmail.com>
Subject: Re: [PATCH] ath10k: remove iteration in wake_tx_queue
Date: Wed, 25 Sep 2019 05:41:07 +0000 (UTC) [thread overview]
Message-ID: <20190925054107.935786119D@smtp.codeaurora.org> (raw)
In-Reply-To: <20190327162906.6010-1-erik.stromdahl@gmail.com>
Erik Stromdahl <erik.stromdahl@gmail.com> wrote:
> Iterating the TX queue and thereby dequeuing all available packets in the
> queue could result in performance penalties on some SMP systems.
>
> The reason for this is most likely that the per-ac lock (active_txq_lock)
> in mac80211 will be held by the CPU iterating the current queue.
>
> This will lock up other CPUs trying to push new messages on the TX
> queue.
>
> Instead of iterating the queue we fetch just one packet at the time,
> resulting in minimal starvation of the other CPUs.
>
> Reported-by: Yibo Zhao <yiboz@codeaurora.org>
> Signed-off-by: Erik Stromdahl <erik.stromdahl@gmail.com>
Like others, I'm not convinced about this either. To me it looks like a quick
workaround instead of properly investigating, and fixing, the root cause. To my
understanding the throughput dip was caused by this commit:
e3148cc5fecf ath10k: fix return value check in wake_tx_q op
So to me it feels like the issue has been there all along, just hidden, and the
fix above just exposed it.
--
https://patchwork.kernel.org/patch/10873753/
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
next prev parent reply other threads:[~2019-09-25 5:41 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-27 16:29 [PATCH] ath10k: remove iteration in wake_tx_queue Erik Stromdahl
2019-03-27 16:29 ` Erik Stromdahl
2019-03-27 17:49 ` Peter Oh
2019-03-27 17:49 ` Peter Oh
2019-03-29 7:47 ` Erik Stromdahl
2019-03-29 7:47 ` Erik Stromdahl
2019-04-01 12:17 ` Yibo Zhao
2019-04-01 12:17 ` Yibo Zhao
2019-04-01 11:05 ` Toke Høiland-Jørgensen
2019-04-01 11:05 ` Toke Høiland-Jørgensen
2019-04-16 18:54 ` Erik Stromdahl
2019-04-16 18:54 ` Erik Stromdahl
2019-04-16 19:07 ` Toke Høiland-Jørgensen
2019-04-16 19:07 ` Toke Høiland-Jørgensen
2019-04-17 13:29 ` Erik Stromdahl
2019-04-17 13:29 ` Erik Stromdahl
2019-04-26 7:07 ` Kalle Valo
2019-04-26 7:07 ` Kalle Valo
2019-09-25 5:41 ` Kalle Valo [this message]
2019-09-25 5:41 ` Kalle Valo
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