linux-kernel - Re: [PATCH 1/2] trace/kprobe: Fix count of missed kretprobes in kprobe

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Message-Id: <20210615144737.087d11e9f901e68cadcb91c5@kernel.org>
Date:   Tue, 15 Jun 2021 14:47:37 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Cc:     <linux-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Anton Blanchard <anton@...abs.org>
Subject: Re: [PATCH 1/2] trace/kprobe: Fix count of missed kretprobes in
 kprobe_profile

On Mon, 14 Jun 2021 23:33:28 +0530
"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> wrote:

> For a kretprobe, the miss count includes the number of times the probe
> on function entry was missed, as well as the number of times we ran out
> of kretprobe_instance structures due to maxactive being too low.
> 
> Fixes: cd7e7bd5e44718 ("tracing: Add kprobes event profiling interface")
> Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>

Good catch!

> ---
>  kernel/trace/trace_kprobe.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index ea6178cb5e334d..0475e2a6d0825e 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -1192,7 +1192,8 @@ static int probes_profile_seq_show(struct seq_file *m, void *v)
>  	seq_printf(m, "  %-44s %15lu %15lu\n",
>  		   trace_probe_name(&tk->tp),
>  		   trace_kprobe_nhit(tk),
> -		   tk->rp.kp.nmissed);
> +		   trace_kprobe_is_return(tk) ? tk->rp.kp.nmissed + tk->rp.nmissed
> +					      : tk->rp.kp.nmissed);

Can you add a static trace_kprobe_nmissed(tk) for wrapping this ?

Thank you,

>  
>  	return 0;
>  }
> -- 
> 2.31.1
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>