DTRACE

NAME

SYNOPSIS

dtrace -s file [OPTIONS]

DESCRIPTION

The dtrace command converts probe descriptions defined in file.d into a probe header file via the -h option or a probe description file via the -G option.

OPTIONS

-h

generate a systemtap header file.

-G

generate a systemtap probe definition object file.

-o file

is the name of the output file. If the -G option is given then the output file will be called file.o; if the -h option is given then the output file will be called file.h.

-C

run the cpp preprocessor on the input file when the -h option is given.

-I file

give this include path to cpp when the -C option is given.

-k

keep temporary files, for example the C language source for the -G option.

EXAMPLES

Systemtap is source compatible with dtrace user application static probe support. Given a file test.d containing:

provider sdt_probes 
{
  probe test_0 (int type);
  probe test_1 (struct astruct node);
};
struct astruct {int a; int b;};

Then the command "dtrace -s test.d -G" will create the probe definition file test.o and the command "dtrace -stest.d -h" will create the probe header file test.h Subsequently the application can use the generated macros this way:

#include "test.h"
 ...
struct astruct s;
 ...
SDT_PROBES_TEST_0(value);
 ...
if (SDT_PROBES_TEST_1_ENABLED())
    SDT_PROBES_TEST_1(expensive_function(s));

SEMAPHORES

Semaphores are flag variables used by probes as a way of bypassing potentially costly processing to prepare arguments for probes that may not even be active. They are automatically set/cleared by systemtap when a relevant script is running, so the argument setup cost is only paid when necessary. These semaphore variables are defined within the the "test.o" object file, which must therefore be linked into an application.

Sometimes, semaphore variables are not necessary nor helpful. Skipping them can simplify the build process, by omitting the extra "test.o" file. To skip dependence upon semaphore variables, include "<sys/sdt.h>" within the application before "test.h":

#include <sys/sdt.h>
#include "test.h"
 ...
struct astruct s;
 ...
SDT_PROBES_TEST_0(value);
 ...
if (SDT_PROBES_TEST_1_ENABLED())
   SDT_PROBES_TEST_1(cheap_function(s));

In this mode, the ENABLED() test is fixed at 1.

SEE ALSO

stap(1),
stappaths(7)

BUGS

error::reporting(7stap), https://sourceware.org/systemtap/wiki/HowToReportBugs

Index

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

EXAMPLES

SEMAPHORES

SEE ALSO

BUGS