linux-kernel - Re: [PATCH] wifi: brcmfmac: remove misleading log messages

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Message-ID: <CAF4oh-MufW98ooTQstJFRF1222hNyOdaCVUaLMpYsRzqo6FGZg@mail.gmail.com>
Date: Fri, 13 Dec 2024 11:35:53 +0300
From: Alex Shumsky <alexthreed@...il.com>
To: Arend van Spriel <arend.vanspriel@...adcom.com>
Cc: linux-wireless@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>, 
	Kalle Valo <kvalo@...nel.org>, brcm80211-dev-list.pdl@...adcom.com, 
	brcm80211@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] wifi: brcmfmac: remove misleading log messages

On Thu, Dec 12, 2024 at 12:30 PM Arend van Spriel
<arend.vanspriel@...adcom.com> wrote:
>
> On 12/9/2024 9:08 PM, Alex Shumsky wrote:
> > On Tue, Nov 26, 2024 at 2:02 PM Arend van Spriel
> > <arend.vanspriel@...adcom.com> wrote:
> >>
> >> On 11/22/2024 7:04 PM, Alex Shumsky wrote:
> >>> Currently when debug info enabled, dmesg spammed every few minutes with
> >>> misleading messages like:
> >>>     brcmf_netdev_start_xmit phy0-sta0: insufficient headroom (0)
> >>>
> >>> Do not log this when headroom is actually sufficient.
> >>
> >> Thanks for your patch. The message may be misleading, but it is actually
> >> information that we need to cow the packet. The zero value indicates
> >> that this is needed because skb_header_cloned(skb) is true. So it is
> >> still useful in my opinion. If you want to make the message less
> >> misleading for that case I would be happy to ack the patch.
> >>
> >> Regards,
> >> Arend
> >
> > Thanks for the review and sorry for the delayed response.
> > Do "%s: clone skb header\n" rephrase make sense to you?
>
> I would say:
>
> brcmf_dbg(INFO, "%s: %s headroom\n", brcmf_ifname(ifp),
>            head_delta ? "insufficient" : "unmodifiable");

Thanks.
Sent [PATCH v2] wifi: brcmfmac: clarify unmodifiable headroom log message.
I'm not sure whether I have to link new version with changed subject,
I haven't found a way

> > I have no deep knowledge of this code, and if you think the original message
> > is actually useful, I'm ok to leave a log message as it is.
> > Initially I had guessed it was an unintentional log message because it has
> > misleading text and logs spammed every few minutes - too rarely to consider
> > It as a real performance issue.
>
> If you enable debug prints you should expect performance impact. If you
> want to capture debug message with negligible performance loss you
> should use ftrace. Debug prints in brcmfmac are setup as trace events.

I expressed my thoughts poorly here.
By "performance issue" I meant the clone process itself, not the log messages.
I have read "insufficient headroom" message as "look, we need to copy headers,
if this happens too often, look into this issue and make it zero-copy"

> Regards,
> Arend