netdev - Re: [PATCH net-next 0/2] net: snmp: tracepoint support for snmp

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Message-ID: <CADxym3YzMGG3gZ1X6gc=qF182Ow0iO+782Hjn3QvnFnRhfEbRA@mail.gmail.com>
Date:   Fri, 12 Nov 2021 14:42:23 +0800
From:   Menglong Dong <menglong8.dong@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     David Miller <davem@...emloft.net>,
        Steven Rostedt <rostedt@...dmis.org>, mingo@...hat.com,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        dsahern@...nel.org, Menglong Dong <imagedong@...cent.com>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 0/2] net: snmp: tracepoint support for snmp

Hello,

On Fri, Nov 12, 2021 at 9:50 AM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Fri, 12 Nov 2021 09:40:47 +0800 Menglong Dong wrote:
> > > I feel like I have seen this idea before. Is this your first posting?
> > >
> > > Would you mind including links to previous discussion if you're aware
> > > of any?
> >
> > This is the first time that I post this patch. Do you mean that someone
> > else has done this before? Sorry, I didn't find it~
>
> I see. Yes, I believe very similar changes were proposed in the past.
>
> I believe that concerns about the performance impact had prevented them
> from being merged.

I have found a similar post:
https://lore.kernel.org/netdev/20090303165747.GA1480@hmsreliant.think-freely.org/

And this is the tracepoint for kfree_skb().

I also concerns about the performance. However, with the tracepoints disabled,
they don't have any impact; with enabled, their impact is no more than the
tracepoint in kfree_skb() and consume_skb().

What's more, I have also realized another version: create tracepoint for every
statistics type, such as snmp_udp_incsumerrors, snmp_udp_rcvbuferrors, etc.
This can solve performance issue, as users can enable part of them, which
may be triggered not frequently. However, too many tracepoint are created, and
I think it may be not applicable.

Thanks!
Menglong Dong