感謝的BlackJack的評論
怎麼樣用C實現它的共享庫,並通過Python中使用它嗎?
庫調用的開銷較小。子進程調用會啓動整個外部進程,並在每次需要該值時將結果作爲字符串通過管道傳遞。共享庫加載一次進入當前進程並將結果傳遞到內存中。
我將它作爲共享庫實現。該庫的源代碼cpucycles.c是(主要基於的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;
}
該代碼通過以下兩個命令編譯成一個共享庫
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
什麼impleme:最後,庫可以被Python在cpucycles.py使用在C中作爲共享庫它,並通過Python中的'ctypes'使用它? – BlackJack
庫調用是否會引入比進程調用更少的開銷?如果是這樣,這可能是一個更有效的方法。不幸的是,它需要更多的我在C中不太熟悉的實現。 – Chickenmarkus
庫調用會減少開銷。子進程調用會啓動整個外部進程,並在每次需要該值時將結果作爲字符串通過管道傳遞。共享庫將_once_加載到當前進程中,並將結果傳遞到內存中。 – BlackJack