netdev - Re: [RFC 0/7] Add support to process rx packets in thread

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Date:   Thu, 23 Jul 2020 12:02:40 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Rakesh Pillai <pillair@...eaurora.org>,
        'Andrew Lunn' <andrew@...n.ch>
Cc:     ath10k@...ts.infradead.org, linux-wireless@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvalo@...eaurora.org,
        johannes@...solutions.net, davem@...emloft.net, kuba@...nel.org,
        netdev@...r.kernel.org, dianders@...omium.org, evgreen@...omium.org
Subject: Re: [RFC 0/7] Add support to process rx packets in thread

On 7/23/20 11:21 AM, Rakesh Pillai wrote:
> 
> 
>> -----Original Message-----
>> From: Florian Fainelli <f.fainelli@...il.com>
>> Sent: Tuesday, July 21, 2020 11:35 PM
>> To: Andrew Lunn <andrew@...n.ch>; Rakesh Pillai <pillair@...eaurora.org>
>> Cc: ath10k@...ts.infradead.org; linux-wireless@...r.kernel.org; linux-
>> kernel@...r.kernel.org; kvalo@...eaurora.org; johannes@...solutions.net;
>> davem@...emloft.net; kuba@...nel.org; netdev@...r.kernel.org;
>> dianders@...omium.org; evgreen@...omium.org
>> Subject: Re: [RFC 0/7] Add support to process rx packets in thread
>>
>> On 7/21/20 10:25 AM, Andrew Lunn wrote:
>>> On Tue, Jul 21, 2020 at 10:44:19PM +0530, Rakesh Pillai wrote:
>>>> NAPI gets scheduled on the CPU core which got the
>>>> interrupt. The linux scheduler cannot move it to a
>>>> different core, even if the CPU on which NAPI is running
>>>> is heavily loaded. This can lead to degraded wifi
>>>> performance when running traffic at peak data rates.
>>>>
>>>> A thread on the other hand can be moved to different
>>>> CPU cores, if the one on which its running is heavily
>>>> loaded. During high incoming data traffic, this gives
>>>> better performance, since the thread can be moved to a
>>>> less loaded or sometimes even a more powerful CPU core
>>>> to account for the required CPU performance in order
>>>> to process the incoming packets.
>>>>
>>>> This patch series adds the support to use a high priority
>>>> thread to process the incoming packets, as opposed to
>>>> everything being done in NAPI context.
>>>
>>> I don't see why this problem is limited to the ath10k driver. I expect
>>> it applies to all drivers using NAPI. So shouldn't you be solving this
>>> in the NAPI core? Allow a driver to request the NAPI core uses a
>>> thread?
>>
>> What's more, you should be able to configure interrupt affinity to steer
>> RX processing onto a desired CPU core, is not that working for you
>> somehow?
> 
> Hi Florian,
> Yes, the affinity of IRQ does work for me.
> But the affinity of IRQ does not happen runtime based on load.

It can if you also run irqbalance.
-- 
Florian