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readprofile 是一个跟踪内核性能的工具，其主要分析schedule/sleep/kvm 这三方面的性能。要使能这个性能需要通过kernel command line传递__setup("profile=", profile_setup);int profile_setup(char *str){	static const char schedstr[] = "schedule";	static const char sleepstr[] = "sleep";	static const char kvmstr[] = "kvm";	int par;	#检查用于是要跟踪哪一个性能，目前只支持三个且同时只能支持一个	if (!strncmp(str, sleepstr, strlen(sleepstr))) {#ifdef CONFIG_SCHEDSTATS		force_schedstat_enabled();		prof_on = SLEEP_PROFILING;		if (str[strlen(sleepstr)] == ',')			str += strlen(sleepstr) + 1;		if (get_option(&str, &par))			prof_shift = par;		pr_info("kernel sleep profiling enabled (shift: %ld)\n",			prof_shift);#else		pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n");#endif /* CONFIG_SCHEDSTATS */	} else if (!strncmp(str, schedstr, strlen(schedstr))) {		prof_on = SCHED_PROFILING;		if (str[strlen(schedstr)] == ',')			str += strlen(schedstr) + 1;		if (get_option(&str, &par))			prof_shift = par;		pr_info("kernel schedule profiling enabled (shift: %ld)\n",			prof_shift);	} else if (!strncmp(str, kvmstr, strlen(kvmstr))) {		prof_on = KVM_PROFILING;		if (str[strlen(kvmstr)] == ',')			str += strlen(kvmstr) + 1;		if (get_option(&str, &par))			prof_shift = par;		pr_info("kernel KVM profiling enabled (shift: %ld)\n",			prof_shift);	} else if (get_option(&str, &par)) {		prof_shift = par;		prof_on = CPU_PROFILING;		pr_info("kernel profiling enabled (shift: %ld)\n",			prof_shift);	}	return 1;}这个函数是profile的初始化的入口函数，可见收集到的数据都是保存在proc/profile 这个目录下int __ref create_proc_profile(void){	entry = proc_create("profile", S_IWUSR | S_IRUGO,			    NULL, &proc_profile_operations);	if (!entry)		goto err_state_onl;	proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));	return err;}static const struct file_operations proc_profile_operations = {	.read		= read_profile,	.write		= write_profile,	.llseek		= default_llseek,};static ssize_tread_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos){	unsigned long p = *ppos;	ssize_t read;	char *pnt;	unsigned int sample_step = 1 << prof_shift;	profile_flip_buffers();	if (p >= (prof_len+1)*sizeof(unsigned int))		return 0;	if (count > (prof_len+1)*sizeof(unsigned int) - p)		count = (prof_len+1)*sizeof(unsigned int) - p;	read = 0;	while (p < sizeof(unsigned int) && count > 0) {		if (put_user(*((char *)(&sample_step)+p), buf))			return -EFAULT;		buf++; p++; count--; read++;	}	pnt = (char *)prof_buffer + p - sizeof(atomic_t);	if (copy_to_user(buf, (void *)pnt, count))		return -EFAULT;	read += count;	*ppos += read;	return read;}我们从read_profile 函数中可以看到保存已经收集的数据是以binary的形式保存的，无法直接分析，因此要用用户态工具readprofile来解析

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