C++获取对应进程的cpu和内存使用情况（支持linux和windows）

运维监控程序中经常需要根据一个进程号pid去监控实时的cpu和内存占用，以下整理了一个C++实现的简单例子，并封装为方便跨平台调用的函数

代码

#include <iostream>
#include <thread>
#include <chrono>
#include <string.h>
#ifdef WIN32
#include <windows.h>
#include <psapi.h>
//#include <tlhelp32.h>
#include <direct.h>
#include <process.h>
#else
#include <sys/stat.h>
#include <sys/sysinfo.h>
#include <sys/time.h>
#include <unistd.h>
#endif
// get current process pid
inline int GetCurrentPid()
{
return getpid();
}
// get specific process cpu occupation ratio by pid
#ifdef WIN32
//
static uint64_t convert_time_format(const FILETIME* ftime)
{
LARGE_INTEGER li;
li.LowPart = ftime->dwLowDateTime;
li.HighPart = ftime->dwHighDateTime;
return li.QuadPart;
}
#else
// FIXME: can also get cpu and mem status from popen cmd
// the info line num in /proc/{pid}/status file
#define VMRSS_LINE 22
#define PROCESS_ITEM 14
static const char* get_items(const char* buffer, unsigned int item)
{
// read from buffer by offset
const char* p = buffer;
int len = strlen(buffer);
int count = 0;
for (int i = 0; i < len; i++)
{
if (' ' == *p)
{
count++;
if (count == item - 1)
{
p++;
break;
}
}
p++;
}
return p;
}
static inline unsigned long get_cpu_total_occupy()
{
// get total cpu use time
// different mode cpu occupy time
unsigned long user_time;
unsigned long nice_time;
unsigned long system_time;
unsigned long idle_time;
FILE* fd;
char buff[1024] = { 0 };
fd = fopen("/proc/stat", "r");
if (nullptr == fd)
return 0;
fgets(buff, sizeof(buff), fd);
char name[64] = { 0 };
sscanf(buff, "%s %ld %ld %ld %ld", name, &user_time, &nice_time, &system_time, &idle_time);
fclose(fd);
return (user_time + nice_time + system_time + idle_time);
}
static inline unsigned long get_cpu_proc_occupy(int pid)
{
// get specific pid cpu use time
unsigned int tmp_pid;
unsigned long utime;
// user time
unsigned long stime;
// kernel time
unsigned long cutime; // all user time
unsigned long cstime; // all dead time
char file_name[64] = { 0 };
FILE* fd;
char line_buff[1024] = { 0 };
sprintf(file_name, "/proc/%d/stat", pid);
fd = fopen(file_name, "r");
if (nullptr == fd)
return 0;
fgets(line_buff, sizeof(line_buff), fd);
sscanf(line_buff, "%u", &tmp_pid);
const char* q = get_items(line_buff, PROCESS_ITEM);
sscanf(q, "%ld %ld %ld %ld", &utime, &stime, &cutime, &cstime);
fclose(fd);
return (utime + stime + cutime + cstime);
}
#endif
inline float GetCpuUsageRatio(int pid)
{
#ifdef WIN32
static int64_t last_time = 0;
static int64_t last_system_time = 0;
FILETIME now;
FILETIME creation_time;
FILETIME exit_time;
FILETIME kernel_time;
FILETIME user_time;
int64_t system_time;
int64_t time;
int64_t system_time_delta;
int64_t time_delta;
// get cpu num
SYSTEM_INFO info;
GetSystemInfo(&info);
int cpu_num = info.dwNumberOfProcessors;
float cpu_ratio = 0.0;
// get process hanlde by pid
HANDLE process = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid);
// use GetCurrentProcess() can get current process and no need to close handle
// get now time
GetSystemTimeAsFileTime(&now);
if (!GetProcessTimes(process, &creation_time, &exit_time, &kernel_time, &user_time))
{
// We don't assert here because in some cases (such as in the Task Manager)
// we may call this function on a process that has just exited but we have
// not yet received the notification.
printf("GetCpuUsageRatio GetProcessTimes failedn");
return 0.0;
}
// should handle the multiple cpu num
system_time = (convert_time_format(&kernel_time) + convert_time_format(&user_time)) / cpu_num;
time = convert_time_format(&now);
if ((last_system_time == 0) || (last_time == 0))
{
// First call, just set the last values.
last_system_time = system_time;
last_time = time;
return 0.0;
}
system_time_delta = system_time - last_system_time;
time_delta = time - last_time;
CloseHandle(process);
if (time_delta == 0)
{
printf("GetCpuUsageRatio time_delta is 0, errorn");
return 0.0;
}
// We add time_delta / 2 so the result is rounded.
cpu_ratio = (int)((system_time_delta * 100 + time_delta / 2) / time_delta); // the % unit
last_system_time = system_time;
last_time = time;
cpu_ratio /= 100.0; // convert to float number
return cpu_ratio;
#else
unsigned long totalcputime1, totalcputime2;
unsigned long procputime1, procputime2;
totalcputime1 = get_cpu_total_occupy();
procputime1 = get_cpu_proc_occupy(pid);
// FIXME: the 200ms is a magic number, works well
usleep(200000); // sleep 200ms to fetch two time point cpu usage snapshots sample for later calculation
totalcputime2 = get_cpu_total_occupy();
procputime2 = get_cpu_proc_occupy(pid);
float pcpu = 0.0;
if (0 != totalcputime2 - totalcputime1)
pcpu = (procputime2 - procputime1) / float(totalcputime2 - totalcputime1); // float number
int cpu_num = get_nprocs();
pcpu *= cpu_num; // should multiply cpu num in multiple cpu machine
return pcpu;
#endif
}
// get specific process physical memeory occupation size by pid (MB)
inline float GetMemoryUsage(int pid)
{
#ifdef WIN32
uint64_t mem = 0, vmem = 0;
PROCESS_MEMORY_COUNTERS pmc;
// get process hanlde by pid
HANDLE process = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid);
if (GetProcessMemoryInfo(process, &pmc, sizeof(pmc)))
{
mem = pmc.WorkingSetSize;
vmem = pmc.PagefileUsage;
}
CloseHandle(process);
// use GetCurrentProcess() can get current process and no need to close handle
// convert mem from B to MB
return mem / 1024.0 / 1024.0;
#else
char file_name[64] = { 0 };
FILE* fd;
char line_buff[512] = { 0 };
sprintf(file_name, "/proc/%d/status", pid);
fd = fopen(file_name, "r");
if (nullptr == fd)
return 0;
char name[64];
int vmrss = 0;
for (int i = 0; i < VMRSS_LINE - 1; i++)
fgets(line_buff, sizeof(line_buff), fd);
fgets(line_buff, sizeof(line_buff), fd);
sscanf(line_buff, "%s %d", name, &vmrss);
fclose(fd);
// cnvert VmRSS from KB to MB
return vmrss / 1024.0;
#endif
}
int main()
{
// launch some task to occupy cpu and memory
for (int i = 0; i < 5; i++)
std::thread([]
{
std::this_thread::sleep_for(std::chrono::milliseconds(10));
}).detach();
int current_pid = GetCurrentPid(); // or you can set a outside program pid
float cpu_usage_ratio = GetCpuUsageRatio(current_pid);
float memory_usage = GetMemoryUsage(current_pid);
while (true)
{
std::cout << "current pid: " << current_pid << std::endl;
std::cout << "cpu usage ratio: " << cpu_usage_ratio * 100 << "%" << std::endl;
std::cout << "memory usage: " << memory_usage << "MB" << std::endl;
std::this_thread::sleep_for(std::chrono::milliseconds(1000));
}
return 0;
}

运行结果

current pid: 17258
cpu usage ratio: 114.286%
memory usage: 8889.9MB

直接使用GetCpuUsageRatio和GetMemoryUsage就行了，有几个说明

• linux下其实是通过读取并解析/proc目录下进程虚拟文件对应字段值计算得到
• windows下调用系统api计算得到
• 这种打点采样获取cpu和内存占用的方式数据跟用系统管理器查看到的不完全一致

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