Callgrind：分析我的代码的特定部分 [英] Callgrind: Profile a specific part of my code

问题描述

我正在尝试（通过Callgrind）通过消除不需要的噪声和计算来分析代码的特定部分。
这是我要执行的操作的示例：

I'm trying to profile (with Callgrind) a specific part of my code by removing noise and computation that I don't care about. Here is an example of what I want to do:

for (int i=0; i<maxSample; ++i) {
    //Prepare data to be processed...
    //Method to be profiled with these data
    //Post operation on the data
}

我的用例是回归测试，我想确保所讨论的方法仍然足够快（自上次实施以来，不到10％的额外指令）。
这就是为什么我要使用更干净的Callgrind输出形式。
（我需要一个for循环，以便处理大量数据，以便对要分析的方法的行为进行良好的估计）

My use-case is a regression test, I want to make sure that the method in question is still fast enough (something like less than 10% extra instructions since the last implementation). This is why I'd like to have the cleaner output form Callgrind. (I need a for loop in order to have a significant amount of data processed in order to have a good estimation of the behavior of the method I want to profile)

我的第一次尝试是将代码更改为：

My first try was to change the code to:

for (int i=0; i<maxSample; ++i) {
    //Prepare data to be processed...
    CALLGRIND_START_INSTRUMENTATION;
    //Method to be profiled with these data
    CALLGRIND_STOP_INSTRUMENTATION;
    //Post operation on the data
}
CALLGRIND_DUMP_STATS;

添加Callgrind宏来控制检测。我还添加了--instr-atstart = no选项，以确保仅对我想要的部分代码进行配置...

Adding the Callgrind macros to control the instrumentation. I also added the --instr-atstart=no options to be sure that I profile only the part of the code I want...

不幸的是，当我使用此配置时开始使用callgrind启动我的可执行文件，但它永远不会结束...这不是缓慢的问题，因为完整的仪器运行持续不到一分钟。

Unfortunately with this configuration when I start to launch my executable with callgrind, it never ends... It is not a question of slowness, because a full instrumentation run last less than one minute.

我还

for (int i=0; i<maxSample; ++i) {
    //Prepare data to be processed...
    CALLGRIND_TOGGLE_COLLECT;
    //Method to be profiled with these data
    CALLGRIND_TOGGLE_COLLECT;
    //Post operation on the data
}
CALLGRIND_DUMP_STATS;

（或--toggle-collect = myMethod选项）
但Callgrind返回了我没有任何调用的日志（KCachegrind像雪一样白:(并说零指令...）

(or the --toggle-collect="myMethod" option) But Callgrind returned me a log without any call (KCachegrind is white as snow :( and says zero instructions...)

我正确使用了宏/选项吗？我需要进行更改才能获得预期的结果？

Did I use the macros/options correctly? Any idea of what I need to change in order to get the expected result?

推荐答案

我终于设法解决了这个问题...配置问题：

I finally managed to solve this issue... This was a config issue:

我保留了代码

for (int i=0; i<maxSample; ++i) {
    //Prepare data to be processed...
    CALLGRIND_TOGGLE_COLLECT;
    //Method to be profiled with these data
    CALLGRIND_TOGGLE_COLLECT;
    //Post operation on the data
}
CALLGRIND_DUMP_STATS;

但是使用-collect-atstart = no （并且没有--instr-atstart = no !!!）运行callgrind，它在合理的时间内（〜1分钟）完美运行。

But ran the callgrind with --collect-atstart=no (and without the --instr-atstart=no!!!) and it worked perfectly, in a reasonable time (~1min).

START /问题STOP工具是callgrind在每次迭代（每次STOP）时都转储一个文件（callgrind.out。＃number），因此它真的很慢...（5分钟后，我只进行了5000次运行30万次迭代的基准测试...不适合进行回归测试）。

The issue with START/STOP instrumentation was that callgrind dumps a file (callgrind.out.#number) at each iteration (each STOP) thus it was really really slow... (after 5min I had only 5000 runs for a 300 000 iterations benchmark... unsuitable for a regression test).

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