Re: [Make-wifi-fast] [PATCH v8 0/2] Implement Airtime-based Queue Limit (AQL)

From: Kalle Valo <kvalo@codeaurora.org>
To: Kan Yan <kyan@google.com>
Cc: "Dave Taht" <dave@taht.net>,
	"Toke Høiland-Jørgensen" <toke@redhat.com>,
	"Rajkumar Manoharan" <rmanohar@codeaurora.org>,
	"Kevin Hayes" <kevinhayes@google.com>,
	Make-Wifi-fast <make-wifi-fast@lists.bufferbloat.net>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	"Yibo Zhao" <yiboz@codeaurora.org>,
	"John Crispin" <john@phrozen.org>,
	"Johannes Berg" <johannes@sipsolutions.net>,
	"Lorenzo Bianconi" <lorenzo@kernel.org>,
	"Felix Fietkau" <nbd@nbd.name>
Subject: Re: [Make-wifi-fast] [PATCH v8 0/2] Implement Airtime-based Queue Limit (AQL)
Date: Wed, 4 Dec 2019 04:47:12 +0000	[thread overview]
Message-ID: <0101016ecf3bc9c2-fe85d3a0-29d8-4854-b227-42552a4f064f-000000@us-west-2.amazonses.com> (raw)
In-Reply-To: <CA+iem5vVGSJXeB8k2n32f=TvqncEj+bOjVbunWS0G8sm_MEosw@mail.gmail.com> (Kan Yan's message of "Tue, 3 Dec 2019 11:02:44 -0800")

Kan Yan <kyan@google.com> writes:

> Dave Taht <dave@taht.net> writes:
>
>> I hope to take a close look at the iwl ax200 chips soon. Unless
>> someone beats me to it. Can we get these sort of stats out of it?
>
> Here is a patch for the trace event I used to get the sojourn time:
> https://drive.google.com/open?id=1Mq8BO_kcneXBqf3m5Rz5xhEMj9jNbcJv
>
> Toke Høiland-Jørgensen <toke@redhat.com> writes:
>
>> While you're running tests, could you do one with the target changed to
>> 10ms, just to see what it looks like? Both sojourn time values and
>> throughput would be interesting here, of course.
>
> Apologize for the late reply. Here is the test results with target set to 10ms.
> The trace for the sojourn time:
> https://drive.google.com/open?id=1MEy_wbKKdl22yF17hZaGzpv3uOz6orTi
>
> Flent test for 20 ms target time vs 10 ms target time:
> https://drive.google.com/open?id=1leIWe0-L0XE78eFvlmRJlNmYgbpoH8xZ
>
> The sojourn time measured during throughput test with a relative good
> 5G connection has mean value around 11 ms, pretty close to the 10 ms
> target.
>
> A smaller CoDel "target" time could help reduce latency, but it may
> drop packets too aggressively for stations with low data rate and
> hurts throughput, as shown in one of the tests with 2.4 GHz client.
>
> Overall, I think AQL and fq_codel works well, at least with ath10k.
> The current target value of 20 ms is a reasonable default.  It is
> relatively conservative that helps stations with weak signal to
> maintain stable throughput. Although, a debugfs entry that allows
> runtime adjustment of target value could be useful.

Why not make it configurable via nl80211? We should use debugfs only for
testing and debugging, not in production builds, and to me the use case
for this value sounds like more than just testing.

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