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From: Kalle Valo <kvalo@kernel.org>
To: Karthikeyan Periyasamy <quic_periyasa@quicinc.com>
Cc: <ath12k@lists.infradead.org>,  <linux-wireless@vger.kernel.org>
Subject: Re: [PATCH 2/3] wifi: ath12k: Optimize the lock contention of used
 list in Rx data path
References: <20240226162310.629162-1-quic_periyasa@quicinc.com>
	<20240226162310.629162-3-quic_periyasa@quicinc.com>
	<87msr4gbps.fsf@kernel.org>
	<33d25f11-d54d-6161-383d-d3823d5f6d19@quicinc.com>
	<874jd3cszc.fsf@kernel.org>
	<1e9c36d9-0a2a-e458-a727-9630746b24e7@quicinc.com>
Date: Tue, 19 Mar 2024 18:44:11 +0200
In-Reply-To: <1e9c36d9-0a2a-e458-a727-9630746b24e7@quicinc.com> (Karthikeyan
	Periyasamy's message of "Tue, 19 Mar 2024 15:07:50 +0530")
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Karthikeyan Periyasamy <quic_periyasa@quicinc.com> writes:

> On 3/18/2024 11:39 PM, Kalle Valo wrote:
>
>> Karthikeyan Periyasamy <quic_periyasa@quicinc.com> writes:
>>
>>> On 3/11/2024 6:35 PM, Kalle Valo wrote:
>>>> Karthikeyan Periyasamy <quic_periyasa@quicinc.com> writes:
>>>>
>>>>> When a packet arrives in Rx rings, the RX descriptor moves from the u=
sed
>>>>> list to the free list. Then, the rxdma ring gets replenished, where t=
he Rx
>>>>> descriptor again moves from the free list to the used list. At the en=
d, the
>>>>> descriptor came to the used list with unnecessary list movement. The
>>>>> descriptor used list is maintained in the Rxdma ring structure, which
>>>>> creates lock contention for the list operations (add, delete) in the =
Rx
>>>>> data path. Optimize the Rx data path by removing the used list from t=
he
>>>>> common Rxdma ring and maintain as a local variable in the Rx ring han=
dler
>>>>> itself, which avoid lock contention. Now, to find the used list descr=
iptor
>>>>> during descriptor cleanup, we need to check the in_use flag for each =
Rx
>>>>> descriptor.
>>>>>
>>>>> Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.0.1-00029-QCAHKSWPL_SILICONZ-1
>>>>>
>>>>> Signed-off-by: Karthikeyan Periyasamy <quic_periyasa@quicinc.com>
>>>> Before looking at this in detail: When optimising something it would be
>>>> good to have before and after numbers showing the improvement. Otherwi=
se
>>>> it's just wishful thinking.
>>> I don't have numbers. Like you said, Its just a wishful think.
>> So do you still want us to take this?
>>
>> In the future please do provide numbers to show that the optimisation
>> really helps as intended. Otherwise we might even go backwards.
>
> This is a simple UDP UL throughput test case results on x86+NUC device
> with QCN9274 card
>
> Before:
> Average:=C2=A0=C2=A0=C2=A0=C2=A0 CPU=C2=A0=C2=A0=C2=A0 %usr=C2=A0=C2=A0 %=
nice=C2=A0=C2=A0=C2=A0 %sys %iowait=C2=A0=C2=A0=C2=A0 %irq=C2=A0=C2=A0 %soft
> %steal=C2=A0 %guest=C2=A0 %gnice=C2=A0=C2=A0 %idle
> Average:=C2=A0=C2=A0=C2=A0=C2=A0 all=C2=A0=C2=A0=C2=A0 0.24=C2=A0=C2=A0=
=C2=A0 0.00=C2=A0=C2=A0 12.54=C2=A0=C2=A0=C2=A0 0.08=C2=A0=C2=A0=C2=A0 0.00=
 23.33=C2=A0=C2=A0=C2=A0
> 0.00=C2=A0=C2=A0=C2=A0 0.00=C2=A0=C2=A0=C2=A0 0.00=C2=A0=C2=A0 63.81
>
> After:
> Average:=C2=A0=C2=A0=C2=A0=C2=A0 CPU=C2=A0=C2=A0=C2=A0 %usr=C2=A0=C2=A0 %=
nice=C2=A0=C2=A0=C2=A0 %sys %iowait=C2=A0=C2=A0=C2=A0 %irq=C2=A0=C2=A0 %soft
> %steal=C2=A0 %guest=C2=A0 %gnice=C2=A0=C2=A0 %idle
> Average:=C2=A0=C2=A0=C2=A0=C2=A0 all=C2=A0=C2=A0=C2=A0 0.34=C2=A0=C2=A0=
=C2=A0 0.00=C2=A0=C2=A0=C2=A0 4.60=C2=A0=C2=A0=C2=A0 0.00=C2=A0=C2=A0=C2=A0=
 0.00 19.59=C2=A0=C2=A0=C2=A0
> 0.00=C2=A0=C2=A0=C2=A0 0.00=C2=A0=C2=A0=C2=A0 0.00=C2=A0=C2=A0 75.47
>
> is it fine to capture in the commit log ?

Thanks, exactly something like that helps to show that the optimisation
is helping. Please also include your analysis of the results in the
commit message.

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