linux-kernel - Re: [RFC][PATCH] tracepoint: Do not waste memory on mods with no tracepoints

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Date:	Wed, 26 Feb 2014 17:20:34 +0000 (UTC)
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC][PATCH] tracepoint: Do not waste memory on mods with no
 tracepoints

----- Original Message -----
> From: "Steven Rostedt" <rostedt@...dmis.org>
> To: "LKML" <linux-kernel@...r.kernel.org>
> Cc: "Ingo Molnar" <mingo@...nel.org>, "Rusty Russell" <rusty@...tcorp.com.au>, "Peter Zijlstra"
> <peterz@...radead.org>, "Mathieu Desnoyers" <mathieu.desnoyers@...icios.com>, "Andrew Morton"
> <akpm@...ux-foundation.org>
> Sent: Wednesday, February 26, 2014 11:03:13 AM
> Subject: [RFC][PATCH] tracepoint: Do not waste memory on mods with no tracepoints
> 
> 
> No reason to allocate tp_module structures for modules that have no
> tracepoints. This just wastes memory.

Good catch! Thanks!

Acked-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>

> 
> Fixes: b75ef8b44b1c "Tracepoint: Dissociate from module mutex"
> Cc: stable@...r.kernel.org # 3.2+
> Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> ---
>  kernel/tracepoint.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
> index 29f2654..0d4ef26 100644
> --- a/kernel/tracepoint.c
> +++ b/kernel/tracepoint.c
> @@ -636,6 +636,9 @@ static int tracepoint_module_coming(struct module *mod)
>  	struct tp_module *tp_mod, *iter;
>  	int ret = 0;
>  
> +	if (!mod->num_tracepoints)
> +		return 0;
> +
>  	/*
>  	 * We skip modules that taint the kernel, especially those with different
>  	 * module headers (for forced load), to make sure we don't cause a crash.
> @@ -679,6 +682,9 @@ static int tracepoint_module_going(struct module *mod)
>  {
>  	struct tp_module *pos;
>  
> +	if (!mod->num_tracepoints)
> +		return 0;
> +
>  	mutex_lock(&tracepoints_mutex);
>  	tracepoint_update_probe_range(mod->tracepoints_ptrs,
>  		mod->tracepoints_ptrs + mod->num_tracepoints);
> --
> 1.8.1.4
> 
> 

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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