dtrace - Online in the Cloud

PROGRAM:

NAME

dtrace - Dtrace compatible user application static probe generation tool.

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.

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