默认情况下，从过程 Jmeter 或顶部返回的值基于样本增量，即它们计算自上一个样本以来的CPU使用率，而不是绝对值。
这对应于在模式下调用时选项-c n to top：

top -c n -l 0 | head -5

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这是默认模式。如果您想要在代码中返回的值，那么您需要基于立即的示例值，使用：

top -c e -l 0 | head -5

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这些值将与您看到的值相对应。
如果你想得到类似的值，以过程 Jmeter /顶部，那么你需要采取两个样本，并显示它们之间的差异值。
例如，我们创建一个包含stats的结构：

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

};

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我们改变printCPUUsage调用，以便执行一个示例：

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;
}

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然后我们取两个样本（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;

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添加printsample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);
}

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因此，当调用printSample(&deltasample)时，它会打印增量记录，它给出的值与top或Activity Monitor所提供的值更相似。
但老实说，我会使用host_statistics，因为代码更简洁：

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];
}

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