linux-kernel - Re: [PATCH net-next] udp: Add tracepoints to monitor skbs going in and out of a UDP socket

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Message-ID: <9724.1538722010@warthog.procyon.org.uk>
Date:   Fri, 05 Oct 2018 07:46:50 +0100
From:   David Howells <dhowells@...hat.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     dhowells@...hat.com, David Ahern <dsahern@...il.com>,
        netdev@...r.kernel.org, linux-afs@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] udp: Add tracepoints to monitor skbs going in and out of a UDP socket

Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:

> - kprobes at the top of the function don't use traps and they've been
> optimized over the years to have very low overhead

To quote kprobes.txt:

	How Does a Kprobe Work?
	-----------------------

	When a kprobe is registered, Kprobes makes a copy of the probed
	instruction and replaces the first byte(s) of the probed instruction
	with a breakpoint instruction (e.g., int3 on i386 and x86_64).

Perhaps the docs need updating.

However, for my purposes, tracepoints are easier.

Anyway, as I said, I don't feel that strongly about the patch.  It was useful
for me, and I thought it might be useful for other people.

David