感谢的BlackJack的评论
怎么样用C实现它的共享库,并通过Python中使用它吗?
库调用的开销较小。子进程调用会启动整个外部进程,并在每次需要该值时将结果作为字符串通过管道传递。共享库加载一次进入当前进程并将结果传递到内存中。
我将它作为共享库实现。该库的源代码cpucycles.c是(主要基于的perf_event_open
's man page的示例):
$ gcc -c -fPIC cpucycles.c -o cpucycles.o
$ gcc -shared -Wl,-soname,libcpucycles.so.1 -o libcpucycles.so.1.0.1 cpucycles.o
:
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/ioctl.h>
#include <linux/perf_event.h>
#include <asm/unistd.h>
static long
perf_event_open(struct perf_event_attr *hw_event, pid_t pid,
int cpu, int group_fd, unsigned long flags)
{
int ret;
ret = syscall(__NR_perf_event_open, hw_event, pid, cpu,
group_fd, flags);
return ret;
}
long long
cpu_cycles(unsigned int microseconds,
pid_t pid,
int cpu,
int exclude_user,
int exclude_kernel,
int exclude_hv,
int exclude_idle)
{
struct perf_event_attr pe;
long long count;
int fd;
memset(&pe, 0, sizeof(struct perf_event_attr));
pe.type = PERF_TYPE_HARDWARE;
pe.size = sizeof(struct perf_event_attr);
pe.config = PERF_COUNT_HW_CPU_CYCLES;
pe.disabled = 1;
pe.exclude_user = exclude_user;
pe.exclude_kernel = exclude_kernel;
pe.exclude_hv = exclude_hv;
pe.exclude_idle = exclude_idle;
fd = perf_event_open(&pe, pid, cpu, -1, 0);
if (fd == -1) {
return -1;
}
ioctl(fd, PERF_EVENT_IOC_RESET, 0);
ioctl(fd, PERF_EVENT_IOC_ENABLE, 0);
usleep(microseconds);
ioctl(fd, PERF_EVENT_IOC_DISABLE, 0);
read(fd, &count, sizeof(long long));
close(fd);
return count;
}
该代码通过以下两个命令编译成一个共享库
import ctypes
import os
cdll = ctypes.cdll.LoadLibrary(os.path.join(os.path.dirname(__file__), "libcpucycles.so.1.0.1"))
cdll.cpu_cycles.argtypes = (ctypes.c_uint, ctypes.c_int, ctypes.c_int,
ctypes.c_int, ctypes.c_int, ctypes.c_int,
ctypes.c_int)
cdll.cpu_cycles.restype = ctypes.c_longlong
def cpu_cycles(duration=1.0, pid=0, cpu=-1,
exclude_user=False, exclude_kernel=False,
exclude_hv=True, exclude_idle=True):
"""
See man page of perf_event_open for all the parameters.
:param duration: duration of counting cpu_cycles [seconds]
:type duration: float
:returns: cpu-cycle count of pid
:rtype: int
"""
count = cdll.cpu_cycles(int(duration*1000000), pid, cpu,
exclude_user, exclude_kernel,
exclude_hv, exclude_idle)
if count < 0:
raise OSError("cpu_cycles(pid={}, duration={}) from {} exited with code {}.".format(
pid, duration, cdll._name, count))
return count
什么impleme:最后,库可以被Python在cpucycles.py使用在C中作为共享库它,并通过Python中的'ctypes'使用它? – BlackJack
库调用是否会引入比进程调用更少的开销?如果是这样,这可能是一个更有效的方法。不幸的是,它需要更多的我在C中不太熟悉的实现。 – Chickenmarkus
库调用会减少开销。子进程调用会启动整个外部进程,并在每次需要该值时将结果作为字符串通过管道传递。共享库将_once_加载到当前进程中,并将结果传递到内存中。 – BlackJack