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trace: Provide a detailed event control interface

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This interface decouples event obtaining from interaction.

Events can be obtained through three different methods:

* identifier
* name
* simple wildcard pattern

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Lluís Vilanova 2013-03-05 14:47:38 +01:00 committed by Stefan Hajnoczi
parent 45be2f5d0d
commit b1bae816c4
4 changed files with 350 additions and 59 deletions
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44
docs/tracing.txt
View file

@ -100,49 +100,37 @@ respectively. This ensures portability between 32- and 64-bit platforms.
== Generic interface and monitor commands ==
You can programmatically query and control the dynamic state of trace events
through a backend-agnostic interface:
You can programmatically query and control the state of trace events through a
backend-agnostic interface provided by the header "trace/control.h".
* trace_print_events
Note that some of the backends do not provide an implementation for some parts
of this interface, in which case QEMU will just print a warning (please refer to
header "trace/control.h" to see which routines are backend-dependent).
* trace_event_set_state
Enables or disables trace events at runtime inside QEMU.
The function returns "true" if the state of the event has been successfully
changed, or "false" otherwise:
#include "trace/control.h"
trace_event_set_state("virtio_irq", true); /* enable */
[...]
trace_event_set_state("virtio_irq", false); /* disable */
Note that some of the backends do not provide an implementation for this
interface, in which case QEMU will just print a warning.
This functionality is also provided through monitor commands:
The state of events can also be queried and modified through monitor commands:
* info trace-events
View available trace events and their state. State 1 means enabled, state 0
means disabled.
* trace-event NAME on|off
Enable/disable a given trace event or a group of events having common prefix
through wildcard.
Enable/disable a given trace event or a group of events (using wildcards).
The "-trace events=<file>" command line argument can be used to enable the
events listed in <file> from the very beginning of the program. This file must
contain one event name per line.
A basic wildcard matching is supported in both the monitor command "trace
-event" and the events list file. That means you can enable/disable the events
having a common prefix in a batch. For example, virtio-blk trace events could
be enabled using:
trace-event virtio_blk_* on
If a line in the "-trace events=<file>" file begins with a '-', the trace event
will be disabled instead of enabled. This is useful when a wildcard was used
to enable an entire family of events but one noisy event needs to be disabled.
Wildcard matching is supported in both the monitor command "trace-event" and the
events list file. That means you can enable/disable the events having a common
prefix in a batch. For example, virtio-blk trace events could be enabled using
the following monitor command:
trace-event virtio_blk_* on
== Trace backends ==
The "tracetool" script automates tedious trace event code generation and also
@ -263,3 +251,7 @@ guard such computations and avoid its compilation when the event is disabled:
}
return ptr;
}
You can check both if the event has been disabled and is dynamically enabled at
the same time using the 'trace_event_get_state' routine (see header
"trace/control.h" for more information).

67
trace/control-internal.h Normal file
View file

@ -0,0 +1,67 @@
/*
* Interface for configuring and controlling the state of tracing events.
*
* Copyright (C) 2011-2012 Lluís Vilanova <vilanova@ac.upc.edu>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#ifndef TRACE__CONTROL_INTERNAL_H
#define TRACE__CONTROL_INTERNAL_H
#include <string.h>
extern TraceEvent trace_events[];
static inline TraceEvent *trace_event_id(TraceEventID id)
{
assert(id < trace_event_count());
return &trace_events[id];
}
static inline TraceEventID trace_event_count(void)
{
return TRACE_EVENT_COUNT;
}
static inline bool trace_event_is_pattern(const char *str)
{
assert(str != NULL);
return strchr(str, '*') != NULL;
}
static inline TraceEventID trace_event_get_id(TraceEvent *ev)
{
assert(ev != NULL);
return ev->id;
}
static inline const char * trace_event_get_name(TraceEvent *ev)
{
assert(ev != NULL);
return ev->name;
}
static inline bool trace_event_get_state_static(TraceEvent *ev)
{
assert(ev != NULL);
return ev->sstate;
}
static inline bool trace_event_get_state_dynamic(TraceEvent *ev)
{
assert(ev != NULL);
return ev->dstate;
}
static inline void trace_event_set_state_dynamic(TraceEvent *ev, bool state)
{
assert(ev != NULL);
assert(trace_event_get_state_static(ev));
return trace_event_set_state_dynamic_backend(ev, state);
}
#endif /* TRACE__CONTROL_INTERNAL_H */

106
trace/control.c
View file

@ -1,19 +1,86 @@
/*
* Interface for configuring and controlling the state of tracing events.
*
* Copyright (C) 2011 Lluís Vilanova <vilanova@ac.upc.edu>
* Copyright (C) 2011-2012 Lluís Vilanova <vilanova@ac.upc.edu>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#include "trace/control.h"
TraceEvent *trace_event_name(const char *name)
{
assert(name != NULL);
TraceEventID i;
for (i = 0; i < trace_event_count(); i++) {
TraceEvent *ev = trace_event_id(i);
if (strcmp(trace_event_get_name(ev), name) == 0) {
return ev;
}
}
return NULL;
}
static bool pattern_glob(const char *pat, const char *ev)
{
while (*pat != '\0' && *ev != '\0') {
if (*pat == *ev) {
pat++;
ev++;
}
else if (*pat == '*') {
if (pattern_glob(pat, ev+1)) {
return true;
} else if (pattern_glob(pat+1, ev)) {
return true;
} else {
return false;
}
} else {
return false;
}
}
while (*pat == '*') {
pat++;
}
if (*pat == '\0' && *ev == '\0') {
return true;
} else {
return false;
}
}
TraceEvent *trace_event_pattern(const char *pat, TraceEvent *ev)
{
assert(pat != NULL);
TraceEventID i;
if (ev == NULL) {
i = -1;
} else {
i = trace_event_get_id(ev);
}
i++;
while (i < trace_event_count()) {
TraceEvent *res = trace_event_id(i);
if (pattern_glob(pat, trace_event_get_name(res))) {
return res;
}
i++;
}
return NULL;
}
void trace_backend_init_events(const char *fname)
{
int ret;
if (fname == NULL) {
return;
}
@ -32,15 +99,28 @@ void trace_backend_init_events(const char *fname)
if ('#' == line_buf[0]) { /* skip commented lines */
continue;
}
if ('-' == line_buf[0]) {
ret = trace_event_set_state(line_buf+1, false);
const bool enable = ('-' != line_buf[0]);
char *line_ptr = enable ? line_buf : line_buf + 1;
if (trace_event_is_pattern(line_ptr)) {
TraceEvent *ev = NULL;
while ((ev = trace_event_pattern(line_ptr, ev)) != NULL) {
if (trace_event_get_state_static(ev)) {
trace_event_set_state_dynamic(ev, enable);
}
}
} else {
ret = trace_event_set_state(line_buf, true);
}
if (!ret) {
fprintf(stderr,
"error: trace event '%s' does not exist\n", line_buf);
exit(1);
TraceEvent *ev = trace_event_name(line_ptr);
if (ev == NULL) {
fprintf(stderr,
"error: trace event '%s' does not exist\n", line_ptr);
exit(1);
}
if (!trace_event_get_state_static(ev)) {
fprintf(stderr,
"error: trace event '%s' is not traceable\n", line_ptr);
exit(1);
}
trace_event_set_state_dynamic(ev, enable);
}
}
}

192
trace/control.h
View file

@ -1,41 +1,193 @@
/*
* Interface for configuring and controlling the state of tracing events.
*
* Copyright (C) 2011 Lluís Vilanova <vilanova@ac.upc.edu>
* Copyright (C) 2011-2012 Lluís Vilanova <vilanova@ac.upc.edu>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#ifndef TRACE_CONTROL_H
#define TRACE_CONTROL_H
#ifndef TRACE__CONTROL_H
#define TRACE__CONTROL_H
#include "qemu-common.h"
#include "trace/generated-events.h"
/** Print the state of all events. */
void trace_print_events(FILE *stream, fprintf_function stream_printf);
/** Set the state of an event.
/**
* TraceEventID:
*
* @return Whether the state changed.
* Unique tracing event identifier.
*
* These are named as 'TRACE_${EVENT_NAME}'.
*
* See also: "trace/generated-events.h"
*/
bool trace_event_set_state(const char *name, bool state);
enum TraceEventID;
/** Initialize the tracing backend.
/**
* trace_event_id:
* @id: Event identifier.
*
* @events Name of file with events to be enabled at startup; may be NULL.
* Corresponds to commandline option "-trace events=...".
* @file Name of trace output file; may be NULL.
* Corresponds to commandline option "-trace file=...".
* @return Whether the backend could be successfully initialized.
* Get an event by its identifier.
*
* This routine has a constant cost, as opposed to trace_event_name and
* trace_event_pattern.
*
* Pre-conditions: The identifier is valid.
*
* Returns: pointer to #TraceEvent.
*
*/
static TraceEvent *trace_event_id(TraceEventID id);
/**
* trace_event_name:
* @id: Event name.
*
* Search an event by its name.
*
* Returns: pointer to #TraceEvent or NULL if not found.
*/
TraceEvent *trace_event_name(const char *name);
/**
* trace_event_pattern:
* @pat: Event name pattern.
* @ev: Event to start searching from (not included).
*
* Get all events with a given name pattern.
*
* Returns: pointer to #TraceEvent or NULL if not found.
*/
TraceEvent *trace_event_pattern(const char *pat, TraceEvent *ev);
/**
* trace_event_is_pattern:
*
* Whether the given string is an event name pattern.
*/
static bool trace_event_is_pattern(const char *str);
/**
* trace_event_count:
*
* Return the number of events.
*/
static TraceEventID trace_event_count(void);
/**
* trace_event_get_id:
*
* Get the identifier of an event.
*/
static TraceEventID trace_event_get_id(TraceEvent *ev);
/**
* trace_event_get_name:
*
* Get the name of an event.
*/
static const char * trace_event_get_name(TraceEvent *ev);
/**
* trace_event_get_state:
* @id: Event identifier.
*
* Get the tracing state of an event (both static and dynamic).
*
* If the event has the disabled property, the check will have no performance
* impact.
*
* As a down side, you must always use an immediate #TraceEventID value.
*/
#define trace_event_get_state(id) \
((id ##_ENABLED) && trace_event_get_state_dynamic(trace_event_id(id)))
/**
* trace_event_get_state_static:
* @id: Event identifier.
*
* Get the static tracing state of an event.
*
* Use the define 'TRACE_${EVENT_NAME}_ENABLED' for compile-time checks (it will
* be set to 1 or 0 according to the presence of the disabled property).
*/
static bool trace_event_get_state_static(TraceEvent *ev);
/**
* trace_event_get_state_dynamic:
*
* Get the dynamic tracing state of an event.
*/
static bool trace_event_get_state_dynamic(TraceEvent *ev);
/**
* trace_event_set_state:
*
* Set the tracing state of an event (only if possible).
*/
#define trace_event_set_state(id, state) \
do { \
if ((id ##_ENABLED)) { \
TraceEvent *_e = trace_event_id(id); \
trace_event_set_state_dynamic(_e, state); \
} \
} while (0)
/**
* trace_event_set_state_dynamic:
*
* Set the dynamic tracing state of an event.
*
* Pre-condition: trace_event_get_state_static(ev) == true
*/
static void trace_event_set_state_dynamic(TraceEvent *ev, bool state);
/**
* trace_event_set_state_dynamic_backend:
*
* Warning: This function must be implemented by each tracing backend.
*/
void trace_event_set_state_dynamic_backend(TraceEvent *ev, bool state);
/**
* trace_print_events:
*
* Print the state of all events.
*
* Warning: This function must be implemented by each tracing backend.
*/
void trace_print_events(FILE *stream, fprintf_function stream_printf);
/**
* trace_backend_init:
* @events: Name of file with events to be enabled at startup; may be NULL.
* Corresponds to commandline option "-trace events=...".
* @file: Name of trace output file; may be NULL.
* Corresponds to commandline option "-trace file=...".
*
* Initialize the tracing backend.
*
* Warning: This function must be implemented by each tracing backend.
*
* Returns: Whether the backend could be successfully initialized.
*/
bool trace_backend_init(const char *events, const char *file);
/** Generic function to initialize the state of events.
/**
* trace_backend_init_events:
* @fname: Name of file with events to enable; may be NULL.
*
* @fname Name of file with events to enable; may be NULL.
* Generic function to initialize the state of events.
*/
void trace_backend_init_events(const char *fname);
#endif /* TRACE_CONTROL_H */
#include "trace/control-internal.h"
#endif /* TRACE__CONTROL_H */