perf_event_open-如何监视多个事件 [英] perf_event_open - how to monitoring multiple events
问题描述
是否有人知道如何设置perf_event_attr结构，该结构可以触发PMU通过perf_event_open()监视多个(类型)事件?
does anyone know how to set perf_event_attr struct that can trigger PMU to monitoring multiple (type) event via perf_event_open()?
类似于perf record -e cycles,faults ls，它具有两种不同的事件类型(PERF_TYPE_HARDWARE和PERF_TYPE_SOFTWARE)，但在
Like perf record -e cycles,faults ls, it has two different event type (PERF_TYPE_HARDWARE and PERF_TYPE_SOFTWARE), but in example on perf_event_open's manpage, perf_event_attr.type can only assigned single value.
任何建议将不胜感激，谢谢！
Any suggestion will be appreciate, thanks!
20170208更新 感谢@gudok为我指明方向，但结果似乎有些异常. 如下所示的演示程序(用于测量整个系统的CPU周期和缓存未命中):
20170208 Update Thanks for @gudok pointing me a direction, but the result seems some abnormal. Demo program as below (for measure whole system's CPU cycle and cache miss):
#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <string.h>
#include <sys/ioctl.h>
#include <linux/perf_event.h>
#include <linux/hw_breakpoint.h>
#include <asm/unistd.h>
#include <errno.h>
#include <stdint.h>
#include <inttypes.h>
#include <time.h>
struct read_format {
uint64_t nr;
struct {
uint64_t value;
uint64_t id;
} values[];
};
int main(int argc, char* argv[]) {
struct perf_event_attr pea;
int fd1, fd2;
uint64_t id1, id2;
uint64_t val1, val2;
char buf[4096];
struct read_format* rf = (struct read_format*) buf;
int i,j;
struct timespec time, time2;
time.tv_sec = 1;
time.tv_nsec = 0;
memset(&pea, 0, sizeof(struct perf_event_attr));
pea.type = PERF_TYPE_HARDWARE;
pea.size = sizeof(struct perf_event_attr);
pea.config = PERF_COUNT_HW_CPU_CYCLES;
pea.disabled = 1;
pea.exclude_kernel = 1;
pea.exclude_hv = 1;
pea.read_format = PERF_FORMAT_GROUP | PERF_FORMAT_ID;
fd1 = syscall(__NR_perf_event_open, &pea, 0, -1, -1, 0);
ioctl(fd1, PERF_EVENT_IOC_ID, &id1);
memset(&pea, 0, sizeof(struct perf_event_attr));
pea.type = PERF_TYPE_HARDWARE;
pea.size = sizeof(struct perf_event_attr);
pea.config = PERF_COUNT_HW_CACHE_MISSES;
pea.disabled = 1;
pea.exclude_kernel = 1;
pea.exclude_hv = 1;
pea.precise_ip = 2; // want to using PEBS
pea.read_format = PERF_FORMAT_GROUP | PERF_FORMAT_ID;
fd2 = syscall(__NR_perf_event_open, &pea, 0, -1, fd1 /*!!!*/, 0);
ioctl(fd2, PERF_EVENT_IOC_ID, &id2);
ioctl(fd1, PERF_EVENT_IOC_RESET, PERF_IOC_FLAG_GROUP);
ioctl(fd1, PERF_EVENT_IOC_ENABLE, PERF_IOC_FLAG_GROUP);
while (1) {
nanosleep(&time, &time2);
//ioctl(fd1, PERF_EVENT_IOC_DISABLE, PERF_IOC_FLAG_GROUP);
read(fd1, buf, sizeof(buf));
for (i = 0; i < rf->nr; i++) {
if (rf->values[i].id == id1) {
val1 = rf->values[i].value;
} else if (rf->values[i].id == id2) {
val2 = rf->values[i].value;
}
}
printf("cpu cycles: %"PRIu64"\n", val1);
printf("cache misses: %"PRIu64"\n", val2);
}
return 0;
}
输出为:
cpu cycles: 120 // Just have about 120 CPU cycles in a second
cache misses: 0 // and doesn't have any cache miss?
cpu cycles: 233
cache misses: 0
cpu cycles: 352
cache misses: 0
cpu cycles: 455
cache misses: 0
cpu cycles: 562
cache misses: 0
cpu cycles: 673
cache misses: 0
cpu cycles: 794
cache misses: 0
cpu cycles: 907
cache misses: 0
cpu cycles: 1011
cache misses: 0
cpu cycles: 1129
cache misses: 3
cpu cycles: 1269
cache misses: 4
cpu cycles: 1423
推荐答案
有点棘手.
我们照常创建第一个计数器.此外，我们传递PERF_FORMAT_GROUP和PERF_FORMAT_ID以便能够同时使用多个计数器.这个柜台将是我们的小组组长.
We create first counter as usual. Additionally, we pass PERF_FORMAT_GROUP and PERF_FORMAT_ID to be able to work with multiple counters simultaneously. This counter will be our group leader.
struct perf_event_attr pea;
int fd1, fd2;
uint64_t id1, id2;
memset(&pea, 0, sizeof(struct perf_event_attr));
pea.type = PERF_TYPE_HARDWARE;
pea.size = sizeof(struct perf_event_attr);
pea.config = PERF_COUNT_HW_CPU_CYCLES;
pea.disabled = 1;
pea.exclude_kernel = 1;
pea.exclude_hv = 1;
pea.read_format = PERF_FORMAT_GROUP | PERF_FORMAT_ID;
fd1 = syscall(__NR_perf_event_open, &pea, 0, -1, -1, 0);
接下来，我们获取第一个计数器的标识符:
Next, we retrieve identifier for the first counter:
ioctl(fd1, PERF_EVENT_IOC_ID, &id1);
第二个(以及所有其他计数器)以相同的方式创建，只有一个例外:我们将fd1值作为组长参数传递:
Second (and all further counters) are created in the same fashion with only one exception: we pass fd1 value as group leader argument:
memset(&pea, 0, sizeof(struct perf_event_attr));
pea.type = PERF_TYPE_SOFTWARE;
pea.size = sizeof(struct perf_event_attr);
pea.config = PERF_COUNT_SW_PAGE_FAULTS;
pea.disabled = 1;
pea.exclude_kernel = 1;
pea.exclude_hv = 1;
pea.read_format = PERF_FORMAT_GROUP | PERF_FORMAT_ID;
fd2 = syscall(__NR_perf_event_open, &pea, 0, -1, fd1, 0); // <-- here
ioctl(fd2, PERF_EVENT_IOC_ID, &id2);
接下来，我们需要声明一个数据结构以一次读取多个计数器.您必须声明不同的字段集，具体取决于传递给perf_event_open的标志.手册页提到了所有可能的字段.在我们的例子中，我们传递了PERF_FORMAT_ID标志，该标志添加了id字段.这将使我们能够区分不同的计数器.
Next we need to declare a data structure to read multiple counters at once. You have to declare different set of fields depending on what flags you pass to perf_event_open. Manual page mentions all possible fields. In our case, we passed PERF_FORMAT_ID flag which adds id field. This will allow us to distinguish between different counters.
struct read_format {
uint64_t nr;
struct {
uint64_t value;
uint64_t id;
} values[/*2*/];
};
现在我们将其称为标准配置ioctl:
Now we call standard profiling ioctls:
ioctl(fd1, PERF_EVENT_IOC_RESET, PERF_IOC_FLAG_GROUP);
ioctl(fd1, PERF_EVENT_IOC_ENABLE, PERF_IOC_FLAG_GROUP);
do_something();
ioctl(fd1, PERF_EVENT_IOC_DISABLE, PERF_IOC_FLAG_GROUP);
最后，我们从组长文件描述符中读取计数器.这两个计数器都以我们声明的单个read_format结构返回:
Finally, we read the counters from group leader file descriptor. Both counters are returned in single read_format structure that we declared:
char buf[4096];
struct read_format* rf = (struct read_format*) buf;
uint64_t val1, val2;
read(fd1, buf, sizeof(buf));
for (i = 0; i < rf->nr; i++) {
if (rf->values[i].id == id1) {
val1 = rf->values[i].value;
} else if (rf->values[i].id == id2) {
val2 = rf->values[i].value;
}
}
printf("cpu cycles: %"PRIu64"\n", val1);
printf("page faults: %"PRIu64"\n", val2);
下面是完整的程序列表:
Below is the full program listing:
#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <string.h>
#include <sys/ioctl.h>
#include <linux/perf_event.h>
#include <linux/hw_breakpoint.h>
#include <asm/unistd.h>
#include <errno.h>
#include <stdint.h>
#include <inttypes.h>
struct read_format {
uint64_t nr;
struct {
uint64_t value;
uint64_t id;
} values[];
};
void do_something() {
int i;
char* ptr;
ptr = malloc(100*1024*1024);
for (i = 0; i < 100*1024*1024; i++) {
ptr[i] = (char) (i & 0xff); // pagefault
}
free(ptr);
}
int main(int argc, char* argv[]) {
struct perf_event_attr pea;
int fd1, fd2;
uint64_t id1, id2;
uint64_t val1, val2;
char buf[4096];
struct read_format* rf = (struct read_format*) buf;
int i;
memset(&pea, 0, sizeof(struct perf_event_attr));
pea.type = PERF_TYPE_HARDWARE;
pea.size = sizeof(struct perf_event_attr);
pea.config = PERF_COUNT_HW_CPU_CYCLES;
pea.disabled = 1;
pea.exclude_kernel = 1;
pea.exclude_hv = 1;
pea.read_format = PERF_FORMAT_GROUP | PERF_FORMAT_ID;
fd1 = syscall(__NR_perf_event_open, &pea, 0, -1, -1, 0);
ioctl(fd1, PERF_EVENT_IOC_ID, &id1);
memset(&pea, 0, sizeof(struct perf_event_attr));
pea.type = PERF_TYPE_SOFTWARE;
pea.size = sizeof(struct perf_event_attr);
pea.config = PERF_COUNT_SW_PAGE_FAULTS;
pea.disabled = 1;
pea.exclude_kernel = 1;
pea.exclude_hv = 1;
pea.read_format = PERF_FORMAT_GROUP | PERF_FORMAT_ID;
fd2 = syscall(__NR_perf_event_open, &pea, 0, -1, fd1 /*!!!*/, 0);
ioctl(fd2, PERF_EVENT_IOC_ID, &id2);
ioctl(fd1, PERF_EVENT_IOC_RESET, PERF_IOC_FLAG_GROUP);
ioctl(fd1, PERF_EVENT_IOC_ENABLE, PERF_IOC_FLAG_GROUP);
do_something();
ioctl(fd1, PERF_EVENT_IOC_DISABLE, PERF_IOC_FLAG_GROUP);
read(fd1, buf, sizeof(buf));
for (i = 0; i < rf->nr; i++) {
if (rf->values[i].id == id1) {
val1 = rf->values[i].value;
} else if (rf->values[i].id == id2) {
val2 = rf->values[i].value;
}
}
printf("cpu cycles: %"PRIu64"\n", val1);
printf("page faults: %"PRIu64"\n", val2);
return 0;
}
这篇关于perf_event_open-如何监视多个事件的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
