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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>
Date: Mon, 18 Mar 2024 20:09:11 +0200
In-Reply-To: <33d25f11-d54d-6161-383d-d3823d5f6d19@quicinc.com> (Karthikeyan
	Periyasamy's message of "Mon, 11 Mar 2024 19:25:10 +0530")
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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 used
>>> list to the free list. Then, the rxdma ring gets replenished, where the Rx
>>> descriptor again moves from the free list to the used list. At the end, 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 the
>>> common Rxdma ring and maintain as a local variable in the Rx ring handler
>>> itself, which avoid lock contention. Now, to find the used list descriptor
>>> 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. Otherwise
>> 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.

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