What is instrumentation point?

I found the concept as in a paper on dynamic instrumentation. But I couldnt find the explanation of this concept. Please explain, if possible...

EDIT: or is there any tutorial on how to achieve lightweight dynamic instrumentation (in user space, for syscalls and normal function calls)?

EDIT(Added paper details):

A code generation approach to optimizing high-performance distributed data stream processing

Abstract:

We present a code-generation-based optimization approach to bringing performance and scalability to distributed stream processing applications. We express stream processing applications using an operator-based, stream-centric language called SPADE, which supports composing distributed data flow graphs out of toolkits of type-generic operators. A major challenge in building such applications is to find an effective and flexible way of mapping the logical graph of operators into a physical one that can be deployed on a set of distributed nodes. This involves finding how best operators map to processes and how best processes map to computing nodes. In this paper, we take a two-stage optimization approach, where an instrumented version of the application is first generated by the SPADE compiler to profile and collect statistics about the processing and communication characteristics of the operators within the application. In the second stage, the profiling information is fed to an optimizer to come up with a physical data flow graph that is deployable across nodes in a computing cluster. This approach not only creates highly optimized applications that are tailored to the underlying computing and networking infrastructure, but also makes it possible to re-target the application to a different hardware setup by simply repeating the optimization step and re-compiling the application to match the physical flow graph produced by the optimizer. Using real-world applications, from diverse domains such as finance and radio-astronomy, we demonstrate the effectiveness of our approach 开发者_JS百科on System S -- a large-scale, distributed stream processing platform.

Instrumentation means inserting code into a stream of instructions whose purpose is to measure something -- execution time, function calls, data access, all sorts of things relating to profiling. That's one of two ways to do profiling, and it's the more accurate but slower one. The other one is sampling, where you periodically interrupt the program and look at its current state. This has less performance impact but isn't as accurate, especially for short runs.

Without knowing what paper you are referencing it is difficult to be sure, but in general it would be a place in the code that has a "hook" for instrumentation.

That is, it is coded so it can be dynamically instrumented, so some measurements can be recorded about how the code runs.

Whether this would be for time spent in a method, power consumption or something else depends on what and how it is being instrumented.

It would be useful to see a link to the paper for the context. In a tool such as systemtap/gdb, an instrumentation point would be any place in the code, whose execution can yield an event. For "dynamic" instrumentation, there is usually no need to compile a hook into the code; the tool just needs to determine a PC address where a breakpoint can be inserted.