linux-kernel - Re: [PATCH 1/3] kobject: add kobject trace points

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Date:   Tue, 6 Sep 2016 14:05:44 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Shuah Khan <shuahkh@....samsung.com>
Cc:     mingo@...hat.com, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] kobject: add kobject trace points

On Tue,  6 Sep 2016 11:49:23 -0600
Shuah Khan <shuahkh@....samsung.com> wrote:

> +#if !defined(_TRACE_KOBJECT_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_KOBJECT_H
> +
> +#include <linux/tracepoint.h>
> +#include <linux/kobject.h>
> +
> +/* kobject_init_class */
> +DECLARE_EVENT_CLASS(kobject_init_class,
> +
> +	TP_PROTO(struct kobject *kobj),
> +
> +	TP_ARGS(kobj),
> +
> +	TP_STRUCT__entry(
> +		__field(void *, kobj)
> +		__field(int, state_initialized)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->kobj = kobj;
> +		__entry->state_initialized = kobj->state_initialized;
> +	),
> +
> +	TP_printk("KOBJECT: %p state=%d",
> +		  __entry->kobj,
> +		  __entry->state_initialized
> +	));
> +
> +/**
> + * kobject_init	- called from kobject_init() when kobject is initialized
> + * @kobj:	- pointer to struct kobject
> + */
> +DEFINE_EVENT(kobject_init_class, kobject_init,
> +
> +	TP_PROTO(struct kobject *kobj),
> +	TP_ARGS(kobj));
> +
> +/* kobject_class */
> +DECLARE_EVENT_CLASS(kobject_class,
> +
> +	TP_PROTO(struct kobject *kobj),
> +	TP_ARGS(kobj),
> +
> +	TP_STRUCT__entry(
> +		__field(void *, kobj)
> +		__string(name, kobject_name(kobj))
> +		__field(int, state_initialized)
> +		__field(void *, parent)
> +		__string(pname, kobj->parent ? kobject_name(kobj->parent) : "")
> +		__field(int, count)
> +	),

state_initialized looks to be a single bit. As you have two dynamic
strings, it may be best to move this around and possibly save 3 bytes.
Also, dynamic strings take 4 bytes, and pointers are 8 bytes on 64 bit
machines, we want to move those too.

	__field(void *, kobj)
	__field(void *, parent)
	__field(int, count)
	__string(name, ...)
	__string(pname, ...)
	__field(char, state_initialized)

This will compact the event a bit better.

-- Steve

> +
> +	TP_fast_assign(
> +		__entry->kobj = kobj;
> +		__assign_str(name, kobject_name(kobj));
> +		__entry->state_initialized = kobj->state_initialized;
> +		__entry->parent = kobj->parent;
> +		__assign_str(pname,
> +			     kobj->parent ? kobject_name(kobj->parent) : "");
> +		__entry->count = atomic_read(&kobj->kref.refcount);
> +	),
> +
> +	TP_printk("KOBJECT: %s (%p) state=%d parent= %s (%p) counter= %d",
> +		  __get_str(name),
> +		  __entry->kobj,
> +		  __entry->state_initialized,
> +		  __get_str(pname),
> +		  __entry->parent,
> +		  __entry->count
> +	));
> +