使用lttng的TRACEPOINT CLASS（truncate怎么用）

接着上篇我们继续学习lttng的功能，本节我们来讲讲lttnp的class功能，废话不多说了，上代码。

[root@ceph-1 test3]# cat tp.h
#undef TRACEPOINT_PROVIDER
#define TRACEPOINT_PROVIDER self_lttng_ust

#undef TRACEPOINT_INCLUDE
#define TRACEPOINT_INCLUDE "tp.h"

#if !defined(TP_H) || defined(TRACEPOINT_HEADER_MULTI_READ)
#define TP_H

#include <lttng/tracepoint.h>

#include "my-struct.h"

TRACEPOINT_EVENT(
	self_lttng_ust,
	main_tracepoint,
	TP_ARGS (
		int32_t, grade,
		const struct student *, student_info
		),

	TP_FIELDS (
		ctf_string(name, student_info->name)
		ctf_integer(int32_t, grade, grade)
		ctf_integer(int32_t, age, student_info->age)
		ctf_float(float, score, student_info->score)
		)
)

TRACEPOINT_EVENT(
	self_lttng_ust,
	main_tracepoint2,
	TP_ARGS (
		int32_t, grade,
		const struct student *, student_info
		),

	TP_FIELDS (
		ctf_string(name, student_info->name)
		ctf_integer(int32_t, grade, grade)
		ctf_integer(int32_t, age, student_info->age)
		ctf_float(float, score, student_info->score)
		)
)

TRACEPOINT_EVENT(
	self_lttng_ust,
	main_tracepoint3,
	TP_ARGS (
		int32_t, grade,
		const struct student *, student_info
		),

	TP_FIELDS (
		ctf_string(name, student_info->name)
		ctf_integer(int32_t, grade, grade)
		ctf_integer(int32_t, age, student_info->age)
		ctf_float(float, score, student_info->score)
		)
)
#endif

#include <lttng/tracepoint-event.h>

[root@ceph-1 test3]# cat my-struct.h
#ifndef MY_STRUCT_H
#define MY_STRUCT_H

#include <stdint.h>

struct student {
    int8_t name[32];
    uint8_t age;
    float score;
};

#endif

[root@ceph-1 test3]# cat tp.c
#define TRACEPOINT_CREATE_PROBES
#define TRACEPOINT_DEFINE

#include "tp.h"

[root@ceph-1 test3]# cat main.c
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include "tp.h"
#include "my-struct.h"

int main(int argc, char *argv[])
{
    struct student s = {
            .name = "sdc",
            .age = 18,
            .score = 123.5
        };
    int32_t grade = 1;

    while(1) {
	grade++;
	tracepoint(self_lttng_ust, main_tracepoint, grade, &s);
	tracepoint(self_lttng_ust, main_tracepoint2, grade, &s);
	tracepoint(self_lttng_ust, main_tracepoint3, grade, &s);
	sleep(1);
    }
    return 0;
}

[root@ceph-1 test3]# cat CMakeLists.txt
cmake_minimum_required(VERSION 3.12)

project(self-ust)

include_directories(${CMAKE_CURRENT_LIST_DIR})

aux_source_directory(. SRC_FILES)

add_executable(${PROJECT_NAME} ${SRC_FILES})

target_link_libraries(${PROJECT_NAME} lttng-ust dl)

mkdir build;
cmake ..
make
./self-ust

[root@ceph-1 tracing]# lttng create my-user-space-session
Session my-user-space-session created.
Traces will be written in /root/lttng-traces/my-user-space-session-20230623-115058

[root@ceph-1 tracing]# lttng enable-event --userspace self_lttng_ust:main_tracepoin*
UST event self_lttng_ust:main_tracepoin* created in channel channel0

[root@ceph-1 tracing]# lttng start
Tracing started for session my-user-space-session

[root@ceph-1 tracing]# lttng stop
Waiting for data availability.
Tracing stopped for session my-user-space-session

[root@ceph-1 tracing]# lttng destroy
Session my-user-space-session destroyed

babeltrace2 ~/lttng-traces/my-user-space-session*
  

我们可以将如上的重复代码进行合并，合并结果如下：

[root@ceph-1 build]# cat ../tp.h
#undef TRACEPOINT_PROVIDER
#define TRACEPOINT_PROVIDER self_lttng_ust

#undef TRACEPOINT_INCLUDE
#define TRACEPOINT_INCLUDE "tp.h"

#if !defined(TP_H) || defined(TRACEPOINT_HEADER_MULTI_READ)
#define TP_H

#include <lttng/tracepoint.h>

#include "my-struct.h"

TRACEPOINT_EVENT_CLASS(
	self_lttng_ust,
	self_lttng_class,
	TP_ARGS (
		int32_t, grade,
		const struct student *, student_info
		),

	TP_FIELDS (
		ctf_string(name, student_info->name)
		ctf_integer(int32_t, grade, grade)
		ctf_integer(int32_t, age, student_info->age)
		ctf_float(float, score, student_info->score)
		)
)

TRACEPOINT_EVENT_INSTANCE(
	self_lttng_ust,
	self_lttng_class,
	main_tracepoint,
	TP_ARGS (
		int32_t, grade,
		const struct student *, student_info
		)
)

TRACEPOINT_EVENT_INSTANCE(
	self_lttng_ust,
	self_lttng_class,
	main_tracepoint2,
	TP_ARGS (
		int32_t, grade,
		const struct student *, student_info
		)
)

TRACEPOINT_EVENT_INSTANCE(
	self_lttng_ust,
	self_lttng_class,
	main_tracepoint3,
	TP_ARGS (
		int32_t, grade,
		const struct student *, student_info
		)
)
#endif

#include <lttng/tracepoint-event.h>

mkdir build;
cmake ..
make
./self-ust

[root@ceph-1 tracing]# lttng create my-user-space-session
Session my-user-space-session created.
Traces will be written in /root/lttng-traces/my-user-space-session-20230623-115058

[root@ceph-1 tracing]# lttng enable-event --userspace self_lttng_ust:main_tracepoin*
UST event self_lttng_ust:main_tracepoin* created in channel channel0

[root@ceph-1 tracing]# lttng start
Tracing started for session my-user-space-session

[root@ceph-1 tracing]# lttng stop
Waiting for data availability.
Tracing stopped for session my-user-space-session

[root@ceph-1 tracing]# lttng destroy
Session my-user-space-session destroyed

babeltrace2 ~/lttng-traces/my-user-space-session*

可以看到效果是一样的，就是简化了，tracepoint provider的写法