ktr(9)

NAME

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

SYNOPSIS

#include <sys/param.h>
#include <sys/ktr.h>
extern int ktrc_pumask;
extern int ktre_ntries;
extern int ktre_xtend;
extern int ktrm_ask;
extern int ktrv_erbose;
extern struct ktre_ntry ktrb_uf[];
void
CTR0(ui_nt mask, char *format);
void
CTR1(ui_nt mask, char *format, arg1);
void
CTR2(ui_nt mask, char *format, arg1, arg2);
void
CTR3(ui_nt mask, char *format, arg1, arg2, arg3);
void
CTR4(ui_nt mask, char *format, arg1, arg2, arg3, arg4);
void
CTR5(ui_nt 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 ktrm_ask. 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 ktre_ntries variable contains the number of entries in the

ktrb_uf
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 ktrm_ask variable contains the run time mask of events to

log.

The CPU event mask is stored in the ktrc_pumask variable.

The ktrv_erbose variable stores the verbose flag that controls

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