netdev - Re: Stacks leading into skb:kfree

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Date: Tue, 18 Jul 2023 15:33:06 -0700
From: Ivan Babrou <ivan@...udflare.com>
To: David Ahern <dsahern@...nel.org>
Cc: Linux Kernel Network Developers <netdev@...r.kernel.org>, kernel-team <kernel-team@...udflare.com>, 
	Eric Dumazet <edumazet@...gle.com>, "David S. Miller" <davem@...emloft.net>, 
	Paolo Abeni <pabeni@...hat.com>, Steven Rostedt <rostedt@...dmis.org>, 
	Masami Hiramatsu <mhiramat@...nel.org>, Jakub Kicinski <kuba@...nel.org>
Subject: Re: Stacks leading into skb:kfree_skb

On Fri, Jul 14, 2023 at 5:54 PM David Ahern <dsahern@...nel.org> wrote:
>
> On 7/14/23 4:13 PM, Ivan Babrou wrote:
> > As requested by Jakub Kicinski and David Ahern here:
> >
> > * https://lore.kernel.org/netdev/20230713201427.2c50fc7b@kernel.org/
> >
> > I made some aggregations for the stacks we see leading into
> > skb:kfree_skb endpoint. There's a lot of data that is not easily
> > digestible, so I lightly massaged the data and added flamegraphs in
> > addition to raw stack counts. Here's the gist link:
> >
> > * https://gist.github.com/bobrik/0e57671c732d9b13ac49fed85a2b2290
>
> I see a lot of packet_rcv as the tip before kfree_skb. How many packet
> sockets do you have running on that box? Can you accumulate the total
> packet_rcv -> kfree_skb_reasons into 1 count -- regardless of remaining
> stacktrace?

Yan will respond regarding the packet sockets later in the day, he
knows this stuff better than I do.

In the meantime, here are the aggregations you requested:

* Normal: https://gist.githubusercontent.com/bobrik/0e57671c732d9b13ac49fed85a2b2290/raw/ae8aa1bc3b22fad6cf541afeb51aa8049d122d02/flamegraph.normal.packet_rcv.aggregated.svg
* Spike: https://gist.githubusercontent.com/bobrik/0e57671c732d9b13ac49fed85a2b2290/raw/ae8aa1bc3b22fad6cf541afeb51aa8049d122d02/flamegraph.spike.packet_rcv.aggregated.svg

I just realized that Github links make flamegraphs non-interactive. If
you download them and open a local copy, they should work better:

* Expand to your screen width
* Working search with highlights
* Tooltips with counts and percentages
* Working zoom