blocks|key|269215|text|非侵入式分析器可以通过分析器将代码编译成可执行形式。该格式不需要与OS所需的实际执行格式匹配。这类似于Java的虚拟机。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|269216|分析器使用一个基本单位，例如时钟周期来测量性能。在确定循环的数量之后，可以将总和乘以一个常量，得到一个近似的时间单位。这个值是近似值，因为程序不是直接在处理器上运行，而是在“虚拟”处理器上运行。|269217|其他分析器修改代码以调用"begin+measurement“和"end+measurement”，其中需要进行分析(通常在函数的开始和结束处)。|269218|当找到特定地址时，JTAG调试器和其他仿真器会调用测量函数。|269219|从嵌入式系统的角度来看，最精确的性能测量技术是找到未使用的引脚或测试点，然后向引脚发送“开始”脉冲，然后发送“结束脉冲”，并使用示波器测量精确的时间差。高级示波器可以提供这种时间差的直方图。|269220|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|N|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|O|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|P|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|K|$]]

A non-intrusive profiler can compile the code into an executable form, by the profiler. This format need not match the actually execution format required by the OS. This is similar to Java's Virtual Machine.

The profiler uses a fundamental unit, such as clock cycles, to measure performace. After determining the amount of cycles, the sum can be multiplied by a constant to come up with an approximate time unit. The value is approximate since the program isn't directly running on a processor, but a "virtual" processor.

Other profilers modify code to call "begin measurement" and "end measurement" where the profiling needs to occur (usually at beginning and ends of functions). 

JTAG debuggers and other emulators call the measurement functions when specific addresses found. 

From an embedded systems perspective, the most accurate performance measurement technique is to find an unused pin or test point, and send a "begin" pulse to the pin and later on an "end-pulse" and use an oscilloscope to measure the exact time difference. Advanced oscilloscopes can provide histograms of this time difference.

blocks|key|727830|text|你在问一个非常重要的问题。然而，根据我所看到的，分析器在许多情况下确实会修改代码。例如，EQUATEC创建了一个可执行文件和库的副本，这些可执行文件和库被插入指令。其他的将在分析器运行时创建代码的缓存和副本。因此，他们不一定要在您正在使用的代码中编写任何插装，而是插装代码或IL的副本。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|727831|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

You are asking a very big question. However from what I have seen profilers do modify the code in many cases. EQUATEC for example creates a copy of your executables and libraries which are instrumented. Others will create caches and copies of the code when the profiler is run. So they are not necessarily writing any instrumentation into the code you are working with but they are instrumenting copies of the code or the IL.

blocks|key|4049187|text|我的猜测是CPU处于“单步模式”。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4049188|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

My guess is that the CPU is put into "single step mode."

blocks|key|269092|text|我能猜到。通常分析器的工具“你的代码，在构建阶段或执行阶段。他们可以把他们的度量调用放在你的函数的开始和结束处。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|269093|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I can guess. Usually profilers 'instruments" your code, on building stage or execution. They can put their measurement calls at the start and at the end of each your function. And do many-many other things.

blocks|key|2647910|text|我不知道quatify，但一种常见的技术是使用随机采样:每100微秒左右中断一次，并保存当前的指令指针。然后从符号表中找出函数所在的位置，并对其求和。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2647911|大多数分析器做的更多，并且还会以某种方式检测代码，以便提供额外的信息。|2647912|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

I don't know about quatify, but one frequent technique is to use
stochastic sampling: interrupt every 100 microseconds or so, and save
the current instruction pointer. Then work out from the symbol table
which function is was in, and totalize those.

Most profilers do a lot more, and will also instrument the code in some
ways, in order to provide additional information.

blocks|key|2647930|text|探查器可能具有以下属性：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2647931|2647932|调试器，它将通知目标进程中的调试事件(如线程创建、DLL加载、线程退出等)。|unordered-list-item|2647933|将有一组钩子(Windows钩子、标准函数调用钩子等)的进程，这些钩子也将用于Windows作为服务运行，它将通知内核(环0)级别的事件。这可能需要也可能不需要硬件虚拟化。|2647934|2647935|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|L|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|M|8|@]|9|@]|A|$]]|$1|F|3|G|5|E|7|N|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|P|8|@]|9|@]|A|$]]]|J|$]]

The profiler may have following attributes:

<ul>
<li>A debugger, which would notice the debugging events in the target process (like thread creation, DLL loading, thread exit etc).</li>
<li>A process that would have set of hooks (Windows hooks, standard function calls hooks etc), which would be used for "profiling".</li>
<li>May run as as a service too which would notice events at kernel (ring 0) level. This may or may not require hardware virtualization from BIOS.</li>
</ul>

blocks|key|269281|text|记住这一点是有帮助的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|269282|269283|探查器的一个重要目的是帮助程序员通过在他/她的代码中定位负责相当大百分比的时间并且可以在更短的时间内完成的活动，从而使他/她的程序尽可能高效。|unordered-list-item|269284|269285|这听起来很明显，对吧？但请注意：|269286|269287|它说的是定位，而不是测量。测量可能是达到定位目的的一种手段，但它实际上是非常间接的。|269288|它说的是活动，而不是函数/方法，也不一定是热点。大多数情况下，这些都是函数调用点，花费的时间比预期的要多，实际上并不需要这样做。|269289|在他/她的代码中这样写道。这是程序员唯一可以修改的代码。知道在某个系统例程中花费了大量的时间是没有好处的。|269290|它说的是时间，而不是CPU时间。如果程序由于I/O或其他系统功能而占用大量时间，这与CPU时间一样重要。|269291|表示大量时间，而不是精确时间。如果一个成本高昂的活动被定位，重要的是它的位置，而不是它的成本有多高的不确定性。(如果你在寻找金块，你会先量一块，然后再找到吗？)|269292|269293|因此，并不是所有的老式取样器或仪器都能达到这个目的。|269294|IMHO，最好的方法是收集堆栈的样本，而不仅仅是程序计数器，并且在随机的挂钟时间采样，而不仅仅是CPU时间，并且不仅按函数报告，而且按代码行报告包含该行的样本的百分比。Zoom就是这样一个分析器。|offset|length|269295|换句话说，a)不要取大量的小样本，并将它们混合在一起形成数字。b)一定要采集少量的大样本，并理解它们告诉你的是什么。|269296|作为一个极端的例子，如果只取三个堆栈样本，如果一个特定的语句(或指令)出现在其中两个堆栈样本的某处，那么该语句的成本是多少？嗯，可以想象这只是一个巧合--一个误报，但平均来说，它将节省(2%2B1)/(3%2B2)+=+60%25的总运行时间。就"bang+for+buck“而言，很难超越这一点。|269297|下面是对the+issues的更详细的总结。|269298|entityMap|0|LINK|mutability|MUTABLE|url|http://www.rotateright.com/|1|http://en.wikipedia.org/wiki/Rule_of_succession|2|https://stackoverflow.com/questions/1777556/alternatives-to-gprof/1779343#1779343^0|0|0|0|0|0|0|0|0|0|0|0|0|0|2C|4|0|0|0|2K|B|1|0|4|A|2|0^^$0|@$1|2|3|4|5|6|7|1I|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|1J|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|1K|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|1L|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|1M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|1N|8|@]|9|@]|A|$]]|$1|J|3|K|5|E|7|1O|8|@]|9|@]|A|$]]|$1|L|3|M|5|E|7|1P|8|@]|9|@]|A|$]]|$1|N|3|O|5|E|7|1Q|8|@]|9|@]|A|$]]|$1|P|3|Q|5|E|7|1R|8|@]|9|@]|A|$]]|$1|R|3|S|5|E|7|1S|8|@]|9|@]|A|$]]|$1|T|3|-4|5|6|7|1T|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|1U|8|@]|9|@]|A|$]]|$1|W|3|X|5|6|7|1V|8|@]|9|@$Y|1W|Z|1X|1|1Y]]|A|$]]|$1|10|3|11|5|6|7|1Z|8|@]|9|@]|A|$]]|$1|12|3|13|5|6|7|20|8|@]|9|@$Y|21|Z|22|1|23]]|A|$]]|$1|14|3|15|5|6|7|24|8|@]|9|@$Y|25|Z|26|1|27]]|A|$]]|$1|16|3|-4|5|6|7|28|8|@]|9|@]|A|$]]]|17|$18|$5|19|1A|1B|A|$1C|1D]]|1E|$5|19|1A|1B|A|$1C|1F]]|1G|$5|19|1A|1B|A|$1C|1H]]]]

It's helpful to keep this in mind:

<ul>
<li>One important purpose of a profiler is to help a programmer make his/her program as efficient as possible by locating activities in his/her code that are responsible for a substantial percent of time and can be done in less time.</li>
</ul>

That sounds obvious, right? But notice:

<ul>
<li>It says locate, not measure. Measuring might be a means to the end of locating, but it's actually very indirect.</li>
<li>It says activities, not functions/methods, and not necessarily hot spots. Most often these are function call points that cost more time than expected, and don't really need to be done.</li>
<li>It says in his/her code. That's the only code the programmer can modify. It does no good to know that a lot of time is spent in some system routine.</li>
<li>It says of time, not of CPU time. If the program spends a substantial percent of time blocked due to I/O or other system functions, that's just as important as CPU time.</li>
<li>It says substantial percent, not precise time. If a costly activity is located, what is important is that it is located, not the uncertainty of how costly it is. (If you are hunting for gold nuggets, do you measure one first, and then find it?)</li>
</ul>

So not just any old sampler or instrumenter will serve this purpose.

IMHO, what works best is something that collects samples of the stack, not just the program counter, and samples at random wall clock time, not just CPU time, and reports not just by function, but by line of code, the percent of samples containing that line.
<a href="http://www.rotateright.com/" rel="nofollow noreferrer">Zoom</a> is such a profiler.

In other words
a) Don't take a large number of small samples and mush them together into numbers.
b) Do take a small number of large samples and understand what they are telling you.

As an extreme example, if as few as three stack samples are taken, if a particular statement (or instruction) appears somewhere on two of them, what does that statement cost?
Well, it's conceivable it's just a coincidence - a false positive, but on average, what it will save is <a href="http://en.wikipedia.org/wiki/Rule_of_succession" rel="nofollow noreferrer">(2+1)/(3+2)</a> = 60% of overall run time.
In terms of "bang for buck", it's hard to beat that.

Here's a more detailed summary of <a href="https://stackoverflow.com/questions/1777556/alternatives-to-gprof/1779343#1779343">the issues</a>.

blocks|key|2639711|text|另一种在嵌入式领域中有用的技术，类似于Thomas+Matthews描述的技术，是将频率发生器连接到将生成NMI+(即，不可屏蔽中断)。然后对作为中断帧的一部分存储在堆栈上的程序计数器进行采样。这将为您的应用程序提供一个非常准确的统计视图，并对您的应用程序进行最少的更改。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2639712|当然，这只适用于特殊情况。|2639713|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Another technique useful in the embedded domain, similar to that descrubed by Thomas Matthews, is to hook up a frequency generator to a pin that will generate an NMI (ie. A non maskable interrupt). Then sample the program counter that was stored on the stack as part of the interrupt frame. This will give a very accurate statistical view of your application with minimal changes to your application. 

Of course this is only applicable in specialised cases.

I would like to know how products like quantify achieve to measure the time spend in functions/methods without modifying the code. Does someone know ?

Do you have web page describing how to start writing your own tool?

How to write a simple code profiler?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我想知道像quantify这样的产品如何在不修改代码的情况下测量函数/方法所花费的时间。有人知道吗？你有描述如何开始编写你自己的工具的网页吗？

问如何编写一个简单的代码分析器？
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