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

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Date:   Thu, 23 Jul 2020 23:51:08 +0530
From:   "Rakesh Pillai" <pillair@...eaurora.org>
To:     "'Florian Fainelli'" <f.fainelli@...il.com>,
        "'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



> -----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.


> --
> Florian