Question

我需要在OS X上获得目标C / C的总CPU空闲时间吗？

如果可能，请提供代码示例。这是我用来获取这些指标的代码。结果百分比与我在Activity Monitor中的百分比不同。所以我假设CPU时间计算不正确：

#include <sys/sysctl.h>
#include <sys/types.h>
#include <mach/mach.h>
#include <mach/processor_info.h>
#include <mach/mach_host.h>

- (void)printCPUUsage
{
    processor_cpu_load_info_t cpuLoad;
    mach_msg_type_number_t processorMsgCount;
    natural_t processorCount;

    uint64_t totalSystemTime = 0, totalUserTime = 0, totalIdleTime = 0, totalCPUTime = 0;

    kern_return_t err = host_processor_info(mach_host_self(), PROCESSOR_CPU_LOAD_INFO, &processorCount, (processor_info_array_t *)&cpuLoad, &processorMsgCount);

    for (natural_t i = 0; i < processorCount; i++) {

        // Calc load types and totals, with guards against 32-bit overflow
        // (values are natural_t)
        uint64_t system = 0, user = 0, idle = 0, total = 0;

        system = cpuLoad[i].cpu_ticks[CPU_STATE_SYSTEM];
        user = cpuLoad[i].cpu_ticks[CPU_STATE_USER];
        idle = cpuLoad[i].cpu_ticks[CPU_STATE_IDLE];

        total = system + user + idle;

        if (total < 1) {
            total = 1;
        }

        totalCPUTime += total;
        totalSystemTime += system;
        totalUserTime += user;
        totalIdleTime += idle;
    }


    double onePercent = totalCPUTime/100.0f;

    NSLog(@"system: %f", (double)totalSystemTime/(double)onePercent);
    NSLog(@"user: %f", (double)totalUserTime/(double)onePercent);
    NSLog(@"idle: %f", (double)totalIdleTime/(double)onePercent);
}

Answer 1

默认情况下，从过程仪表或顶部返回的值是基于样本增量，即它们计算自上一个样本以来的CPU使用率，而不是绝对值。

在模式中调用时，这对应于选项-c n：

 top -c n -l 0 | head -5

这是默认模式。如果您想要在代码中返回的值，那么您需要使用以下方法将值基于立即样本：

 top -c e -l 0 | head -5

这些值将与您看到的值相对应。

如果要获得与过程仪表/顶部相似的值，则需要采样两个样本，并显示它们之间差异的值。

例如，我们创建一个包含统计信息的结构：

struct cpusample {
    uint64_t totalSystemTime;
    uint64_t totalUserTime;
    uint64_t totalIdleTime;

};

我们改变了printCPUUsage调用，以便它执行一个示例：

void sample(struct cpusample *sample)
{
    processor_cpu_load_info_t cpuLoad;
    mach_msg_type_number_t processorMsgCount;
    natural_t processorCount;

    uint64_t totalSystemTime = 0, totalUserTime = 0, totalIdleTime = 0;

    kern_return_t err = host_processor_info(mach_host_self(), PROCESSOR_CPU_LOAD_INFO, &processorCount, (processor_info_array_t *)&cpuLoad, &processorMsgCount);

    for (natural_t i = 0; i < processorCount; i++) {

        // Calc load types and totals, with guards against 32-bit overflow
        // (values are natural_t)
        uint64_t system = 0, user = 0, idle = 0;

        system = cpuLoad[i].cpu_ticks[CPU_STATE_SYSTEM];
        user = cpuLoad[i].cpu_ticks[CPU_STATE_USER] + cpuLoad[i].cpu_ticks[CPU_STATE_NICE];
        idle = cpuLoad[i].cpu_ticks[CPU_STATE_IDLE];

        totalSystemTime += system;
        totalUserTime += user;
        totalIdleTime += idle;
    }
    sample->totalSystemTime = totalSystemTime;
    sample->totalUserTime = totalUserTime;
    sample->totalIdleTime = totalIdleTime;
}

然后我们采取两个样本（样本之间1秒）：

struct cpusample delta;
sample(&sample1);
sleep(1);
sample(&sample2);
deltasample.totalSystemTime = sample2.totalSystemTime - sample1.totalSystemTime;
deltasample.totalUserTime = sample2.totalUserTime - sample1.totalUserTime;
deltasample.totalIdleTime = sample2.totalIdleTime - sample1.totalIdleTime;

添加打印样本代码：

void printSample(struct cpusample *sample)
{
    uint64_t total = sample->totalSystemTime + sample->totalUserTime + sample->totalIdleTime;

    double onePercent = total/100.0f;

    NSLog(@"system: %f", (double)sample->totalSystemTime/(double)onePercent);
    NSLog(@"user: %f", (double)sample->totalUserTime/(double)onePercent);
    NSLog(@"idle: %f", (double)sample->totalIdleTime/(double)onePercent);
}

因此，当您调用printSample(&deltasample)时，它会打印增量记录，该记录的值与top或Activity Monitor提供的值相似。

但说实话，我会使用host_statistics，因为代码更清晰：

void sample(struct cpusample *sample)
{
    kern_return_t kr;
    mach_msg_type_number_t count;
    host_cpu_load_info_data_t r_load;

    uint64_t totalSystemTime = 0, totalUserTime = 0, totalIdleTime = 0;

    count = HOST_CPU_LOAD_INFO_COUNT;
    kr = host_statistics(mach_host_self(), HOST_CPU_LOAD_INFO, (int *)&r_load, &count);
    if (kr != KERN_SUCCESS) {
        printf("oops: %s\n", mach_error_string(kr));
        return;
    }

    sample->totalSystemTime = r_load.cpu_ticks[CPU_STATE_SYSTEM];
    sample->totalUserTime = r_load.cpu_ticks[CPU_STATE_USER] + r_load.cpu_ticks[CPU_STATE_NICE];
    sample->totalIdleTime = r_load.cpu_ticks[CPU_STATE_IDLE];
}

如何在OS X上以Objective C / C获得总CPU空闲时间？

1 个答案: