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From: Taeung Song <treeze.taeung@gmail.com>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: linux-trace-users@vger.kernel.org,
	"David S. Miller" <davem@davemloft.net>
Subject: Re: How to recheck 'maxactive' ?
Date: Mon, 23 Mar 2020 21:54:24 +0900	[thread overview]
Message-ID: <0dbeb5a0-2834-0f74-66cb-839d5cbf64f9@gmail.com> (raw)
In-Reply-To: <20200323154741.0643126b3684c950bb37bf7e@kernel.org>

Hi Masami,

Thank you for the reply!
And your patch looks great.

Thanks,
Taeung

On 3/23/20 3:47 PM, Masami Hiramatsu wrote:
> Hi Taeung,
> 
> On Sun, 22 Mar 2020 23:06:20 +0900
> Taeung Song <treeze.taeung@gmail.com> wrote:
> 
>> Hi,
>>
>> After setting 'maxactive' for kretprobe,
>> how can I recheck the value of 'maxactive' ?
>> For example, in order to distinguish the difference
>> between two kretprobe events
>> (kmem_cache_alloc_node and kmem_cache_alloc_node10)
>>
>>     $ cd /sys/kernel/debug/tracing
>>     $ echo 'r:kmem_cache_alloc_node kmem_cache_alloc_node' >> kprobe_events
>>     $ echo 'r10:kmem_cache_alloc_node10 kmem_cache_alloc_node' >>
>> kprobe_events
>>
>>     $ cat kprobe_events
>>     r:kprobes/kmem_cache_alloc_node kmem_cache_alloc_node
>>     r:kprobes/kmem_cache_alloc_node10 kmem_cache_alloc_node
> 
> Oops! good catch. That must be a bug, since the kprobe_events design policy
> is to support following operation.
> 
> $ cat kprobe_events > /etc/event_setting
> (reboot)
> $ cat /etc/event_setting > kprobe_events
> 
> What about below patch?
> 
>  From 935ed56819f2bfb7ac977f5c63273c9a6e3dfb42 Mon Sep 17 00:00:00 2001
> From: Masami Hiramatsu <mhiramat@kernel.org>
> Date: Mon, 23 Mar 2020 10:57:48 +0900
> Subject: [PATCH] ftrace/kprobe: Show the maxactive number on kprobe_events
> 
> Show maxactive parameter on kprobe_events.
> This allows user to save the current configuration and
> restore it without losing maxactive parameter.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
>   kernel/trace/trace_kprobe.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 362cca52f5de..d0568af4a0ef 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -1078,6 +1078,8 @@ static int trace_kprobe_show(struct seq_file *m, struct dyn_event *ev)
>   	int i;
>   
>   	seq_putc(m, trace_kprobe_is_return(tk) ? 'r' : 'p');
> +	if (trace_kprobe_is_return(tk) && tk->rp.maxactive)
> +		seq_printf(m, "%d", tk->rp.maxactive);
>   	seq_printf(m, ":%s/%s", trace_probe_group_name(&tk->tp),
>   				trace_probe_name(&tk->tp));
>   
> 

  reply	other threads:[~2020-03-23 12:54 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-22 14:06 How to recheck 'maxactive' ? Taeung Song
2020-03-23  6:47 ` Masami Hiramatsu
2020-03-23 12:54   ` Taeung Song [this message]
2020-03-23 13:04   ` Steven Rostedt
2020-03-24  6:40     ` Masami Hiramatsu

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