测量库调用和回调之间的时间 [英] Measure time between library call and callback

问题描述

嗨：在iPhone应用程序中，我使用了一个库（C ++），它在计算完成时异步进行回调。
现在我想测量花费的时间 - 包括调用库的方法 - 直到进行回调。有没有可能使用Apple的Instruments应用程序执行此操作？什么是最佳实践？

Hi: In an iPhone application I use a library(C++) which asynchronously makes a callback when computation is finished. Now I want to measure the time which is spent -including the method which calls the library- until the callback is made. Are there any possibilities to do this with the Instruments application from Apple? What are the best practices?

推荐答案

过去我使用以下方法进行网络调用我必须优化 - 尽管在首先它似乎有点复杂，它肯定给出了我见过的最准确的时间。

In the past I have used the following for making network calls I had to optimize - although at first it seems a bit convoluted, it certainly gives the most accurate times I have seen.

uint64_t time_a = mach_absolute_time();

// do stuff

uint64_t time_b = mach_absolute_time();

[self logTime:(time_b-time_a)];

- (void) logTime:(uint64_t)machTime {
    static double timeScaleSeconds = 0.0;
    if (timeScaleSeconds == 0.0) {
        mach_timebase_info_data_t timebaseInfo;
        if (mach_timebase_info(&timebaseInfo) == KERN_SUCCESS) {
            double timeScaleMicroSeconds = ((double) timebaseInfo.numer / (double) timebaseInfo.denom) / 1000;
            timeScaleSeconds = timeScaleMicroSeconds / 1000000;
        }
    }

    NSLog(@"%g seconds", timeScaleSeconds*machTime);
}

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