[DTrace-devel] [Patch] Example to list and count function calls

[Eugene Loh]

Reviewed-by: Eugene Loh <eugene.loh at oracle.com>
The problem with all these examples is knowing who the target audience 
is.  Alas, so be it.
We've (for awkward reasons) been duplicating patch emails on both this 
list and dtrace at lists.linux.dev.
We need to figure out where a file/example like this will live.
But the example itself looks reasonable enough.

On 7/24/25 03:08, Ruud van der Pas via DTrace-devel wrote:
> This example program is called fcalls.d. It lists and gives call counts
> for the functions that are executed when running the target program.
> This information is shown for the individual threads, as well as
> aggregated over the threads.
>
> Ruud
>
> #!/usr/sbin/dtrace -s
>
> /*
> *  NAME
> *    fcalls.d - list the functions executed by an application
> *
> *  SYNOPSIS
> *    sudo ./fcalls.d -c "<name-of-application> [app options]"
> *
> *  DESCRIPTION
> *    This program lists the functions executed by the target
> *    application.  In addition to this, the number of calls to
> *    each function is printed.  This information is given on a
> *    per-thread basis, as well as aggregated over all threads.
> *
> *  NOTES
> *    - Since a.out is used in the probe definitions, library calls
> *    are excluded.  If a library like libc should be included,
> *    duplicate the probe definitions and in the copied lines
> *    replace a.out by libc.so.
> *    For example:
> *    pid$target:a.out::entry,pid$target:libc.so::entry
> *      { ... }
> *    - It is assumed that a function called main is executed.
> *    If this is not the case, this is not a critical error.
> *    The first probe is used to capture the name of the executable,
> *    but this is not critical.  The probe and printf statement
> *    can safely be removed, or replaced by a suitable alternative.
> */
>
> /*
> *  Suppress the default output from the dtrace command and
> *  have printa() print the data sorted by the first field.
> */
> #pragma D option quiet
> #pragma D option aggsortkey=1
> #pragma D option aggsortkeypos=0
>
> /*
> *  Store the name of the target application.  The probe
> *  is restricted to main only, because the exec name needs
> *  to be captured only once.
> */
> pid$target:a.out:main:entry
> {
>   executable_name = execname;
> }
> /*
> *  Use 4 aggregations to store the total number of function
> *  calls, the counts per function and per thread, both
> *  seperately and differentiated by thread and function.
> */
> pid$target:a.out::entry
> {
>   @total_call_counts                          = count();
>   @call_counts_per_function[probefunc]        = count();
>   @call_counts_per_thr[tid]                   = count();
>   @counts_per_thr_and_function[tid,probefunc] = count();
> }
> /*
> *  Print the results.  Use format strings to create a
> *  table lay-out.
> */
> END {
>   printf("===========================================\n");
>   printf("      Function Call Count Statistics\n");
>   printf("===========================================\n");
>   printf("Name of the executable: %s\n" ,executable_name);
>   printa("Total function calls  : %@d\n", at total_call_counts);
>
>   printf("\n===========================================\n");
>   printf("      Aggregated Function Call Counts\n");
>   printf("===========================================\n");
>   printf("%-25s %12s\n\n","Function name","Count");
>   printa("%-25s %@12d\n", at call_counts_per_function);
>
>   printf("\n===========================================\n");
>   printf("      Function Call Counts Per Thread\n");
>   printf("===========================================\n");
>   printf("%-7s %12s\n\n", "TID","Count");
>   printa("%-7d %@12d\n", at call_counts_per_thr);
>
>   printf("\n===========================================\n");
>   printf("      Thread Level Function Call Counts\n");
>   printf("===========================================\n");
>   printf("%-7s  %-25s %8s\n\n","TID","Function name","Count");
>   printa("%-7d  %-25s %@8d\n", at counts_per_thr_and_function);
> }
>
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