What is the difference between flat profile and call graph in the output generated by gprof?

The flat profile is the most useful output table in line-by-line mode. The call graph isn’t as useful as normal, since the current version of gprof does not propagate call graph arcs from source code lines to the enclosing function.

What is call graph profiling?

In call graph profiling, time used by each subroutine is also charged to its callers in order to give a better idea of how the time is divided among major tasks in the program. Submitted to PLDI 2002 during execution; that is, the number of times each routine calls each of its subroutines.

How do you read a Callgraph?

How to Read the Call Graph

1. Primary: Details of the primary line’s contents.
2. Callers: Details of caller-lines’ contents.
3. Subroutines: Details of subroutine-lines’ contents.
4. Cycles: When there are cycles of recursion, such as a calls b calls a …

How does Gprof work?

Gprof works by automatically instrumenting your code during compilation, and then sampling the application’s program counter during execution. Sampling data is saved in a file, typically named gmon. Gprof was developed as an extension of the prof command, by providing a call graph of the program’s execution.

How accurate is Gprof?

They are completely accurate and will not vary from run to run if your program is deterministic. The sampling period that is printed at the beginning of the flat profile says how often samples are taken. The rule of thumb is that a run-time figure is accurate if it is considerably bigger than the sampling period.

How do I enable Gprof?

EXAMPLES

1. Enable profiling during compilation (use -pg option) $ gcc -pg -o TestGprof TestGprof.c.
2. Execute the binary so that profiling data is generated. $ ./TestGprof. If the profiling is enabled then on executing the program, file gmon.
3. Run gprof on profiling data. $ gprof -b TestGprof gmon.out > analysis.out.

What is function call graph?

Blackfire records the functions called during the execution of a program and their relationships as a call graph. A call graph knows nothing about when a function was called, but it reports the sequence of calls between functions.

What is a Java call graph?

The Java Call Graph presents the chain of possible calls at runtime in Java. The nodes in the graph represent the project components, while the edges (arrows) represent relationships between the components. Both nodes and edges are color coded to show the type of component or relationship.

What is function call tree?

A call tree is a layered hierarchical communication model that is used to notify specific individuals of an event and coordinate recovery, if necessary. A call tree is also known as a phone tree, call list, phone chain or text chain. Call trees play an important role in disaster recovery plans.

What is Gprof in Linux?

DESCRIPTION. gprof produces an execution profile of C, Pascal, or Fortran77 programs. The effect of called routines is incorporated in the profile of each caller. The profile data is taken from the call graph profile file (gmon.

What is Mcount?

The mcount routine, included in the profiling library, is responsible for recording in an in-memory call graph table both its parent routine (the child) and its parent’s parent. This is typically done by examining the stack frame to find both the address of the child, and the return address in the original parent.

How do you generate GMON?

It can be done by running the gprof command with the -c option on the call graph profile file (gmon. out by default) to generate a file (gprof. remote by default), which can then be processed on a remote machine.

How does the call graph in gprof work?

The -c option causes the call graph of the program to be augmented by a heuristic which examines the text space of the object file and identifies function calls in the binary machine code. Since normal call graph records are only generated when functions are entered, this option identifies children that could have been called, but never were.

Is the flat profile mentioned in the call graph?

The internal profiling function mcount (see section The Flat Profile ) is never mentioned in the call graph. The primary line in a call graph entry is the line that describes the function which the entry is about and gives the overall statistics for this function.

Which is Better Call graph or call graph?

On the other hand, call graph focuses on each function like the functions through which a particular function was called, what all functions were called from within this particular function etc So this way one can get idea of the execution time spent in the sub-routines too.

What happens to the flat profile listing in gprof?

The flat profile listing is sorted first by this number. This is the total number of times the function was called. If the function was never called, or the number of times it was called cannot be determined (probably because the function was not compiled with profiling enabled), the calls field is blank.