Re: [PATCH 2/2] tracing, perf : add cpu hotplug trace events

[Frederic Weisbecker <fweisbec@gmail.com>]

On Tue, Jan 25, 2011 at 09:54:59AM +0100, Vincent Guittot wrote:
> Please find below a new proposal for adding trace events for cpu hotplug.
> The goal is to measure the latency of each part (kernel, architecture)
> and also to trace the cpu hotplug activity with other power events. I
> have tested these traces events on an arm platform.
> 
> Subject: [PATCH 1/2] add cpu hotplug tracepoints
> 
> this patch adds new events for cpu hotplug tracing
>  * plug/unplug sequence
>  * core and architecture latency measurements
> 
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
> ---
>  kernel/cpu.c |   17 +++++++++++++++++
>  1 files changed, 17 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index 156cc55..f04e9cf 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -16,6 +16,9 @@
>  #include <linux/mutex.h>
>  #include <linux/gfp.h>
> 
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/cpu_hotplug.h>
> +
>  #ifdef CONFIG_SMP
>  /* Serializes the updates to cpu_online_mask, cpu_present_mask */
>  static DEFINE_MUTEX(cpu_add_remove_lock);
> @@ -200,7 +203,9 @@ static int __ref take_cpu_down(void *_param)
>  	int err;
> 
>  	/* Ensure this CPU doesn't handle any more interrupts. */
> +	trace_cpu_hotplug_arch_disable_start((unsigned int)(param->hcpu));
>  	err = __cpu_disable();
> +	trace_cpu_hotplug_arch_disable_end((unsigned int)(param->hcpu));

You should create a cpu var instead of doing that not very beautiful cast
twice.

Probably we should eventually rename arch_disable into just disable.

And same for die, because otherwise the name is quite long.

Other than that, looks all good to me.

Thanks.