ktr(9)

NAME

CTR0, CTR1, CTR2, CTR3, CTR4, CTR5 - kernel tracing facility

SYNOPSIS

#include <sys/param.h>
#include <sys/ktr.h>
extern int ktr_cpumask;
extern int ktr_entries;
extern int ktr_extend;
extern int ktr_mask;
extern int ktr_verbose;
extern struct ktr_entry ktr_buf[];
void
CTR0(u_int mask, char *format);
void
CTR1(u_int mask, char *format, arg1);
void
CTR2(u_int mask, char *format, arg1, arg2);
void
CTR3(u_int mask, char *format, arg1, arg2, arg3);
void
CTR4(u_int mask, char *format, arg1, arg2, arg3, arg4);
void
CTR5(u_int  mask,  char  *format,  arg1,  arg2,  arg3, arg4,
arg5);

DESCRIPTION

KTR provides a circular buffer of events that can be logged

in a
printf(9) style fashion. These events can then be dumped

with ddb(4),
gdb(1) or ktrdump(8).

Events are created and logged in the kernel via the CTRx

macros. The
first parameter is a mask of event types (KTR_*) defined in

The event
will be logged only if any of the event types specified in

mask are
enabled in the global event mask stored in ktr_mask. The

format argument
is a printf(9) style format string used to build the text of

the event
log message. Following the format string are zero to five

arguments referenced by format. Note that the different macros differ

only in the
number of arguments each one takes, as indicated by its

name. Each event
is logged with a timestamp in addition to the log message.

The ktr_entries variable contains the number of entries in

the ktr_buf
array. These variables are mostly useful for post-mortem

crash dump
tools to locate the base of the circular trace buffer and

its length.

The ktr_mask variable contains the run time mask of events

to log.

The CPU event mask is stored in the ktr_cpumask variable.

The ktr_verbose variable stores the verbose flag that con

trols whether
events are logged to the console in addition to the event

buffer.

EXAMPLES

This example demonstrates the use of tracepoints at the

KTR_PROC logging
level.

void
mi_switch()
{

...
/*

* Pick a new current process and record its start

time.
*/

...
CTR3(KTR_PROC, "mi_switch: old proc %p (pid %d,

%s)", p, p->p_pid,

p->p_comm);

...
cpu_switch();
...
CTR3(KTR_PROC, "mi_switch: new proc %p (pid %d,

%s)", p, p->p_pid,

p->p_comm);

...

}

SEE ALSO

ktr(4), ktrdump(8)

HISTORY

The KTR kernel tracing facility first appeared in BSD/OS 3.0

and was
imported into FreeBSD 5.0.

BUGS

Currently there is one global buffer shared among all CPUs.

It might be
profitable at some point in time to use per-CPU buffers in

stead so that
if one CPU halts or starts spinning, then the log messages

it emitted
just prior to halting or spinning will not be drowned out by

events from
the other CPUs.

BSD February 15, 2001

BSD