[Qemu-devel] [RFC v4][PATCH 0/3] Monitor support for Qemu tracing

[Qemu-devel] [RFC v4][PATCH 0/3] Monitor support for Qemu tracing

[Prerna Saxena]

This set of patches enables trace visualization & control 
via the QEMU monitor. It is based on trace infrastructure posted 
upstream :
( http://lists.gnu.org/archive/html/qemu-devel/2010-05/msg02407.html )

This patchset adds monitor commands :
- info trace : to view current contents of the trace buffer
- info tracepoints : to view all available tracepoints and their state.
- tracepoint NAME on|off : to enable/disable the logging of dataThis is v3 of a set of patches to enable trace visualization & control 
via the QEMU monitor. 

Changelog from v3:
1. As suggested, it replaces a hash-based search of tracepoints 
with a linear search.
2. Static initialization of trace event array.
3. Cleanups.

Changelog from v2:
1. Clean-ups, particularly relating to export of tdb_hash().

Changelog from v1:
1. Command 'info trace' is used to view current contents of buffer, in 
place of 'trace'.
2. Cleanups


Todos :
1. Integration with QMP
2. More tracepoints need to be added for instrumenting other qemu components
 such as virtio drivers, etc.

-- 
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India

[Qemu-devel] [RFC v4][PATCH 1/3] Change type declarations

[Prerna Saxena]

Change type 'TraceEvent' to 'TraceEventID'

Signed-off-by: Prerna Saxena <prerna@linux.vnet.ibm.com>
---
 simpletrace.c |   12 ++++++------
 tracetool     |   12 ++++++------
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/simpletrace.c b/simpletrace.c
index 2fec4d3..b488380 100644
--- a/simpletrace.c
+++ b/simpletrace.c
@@ -19,7 +19,7 @@ static TraceRecord trace_buf[TRACE_BUF_LEN];
 static unsigned int trace_idx;
 static FILE *trace_fp;
 
-static void trace(TraceEvent event, unsigned long x1,
+static void trace(TraceEventID event, unsigned long x1,
                   unsigned long x2, unsigned long x3,
                   unsigned long x4, unsigned long x5) {
     TraceRecord *rec = &trace_buf[trace_idx];
@@ -43,22 +43,22 @@ static void trace(TraceEvent event, unsigned long x1,
     }
 }
 
-void trace1(TraceEvent event, unsigned long x1) {
+void trace1(TraceEventID event, unsigned long x1) {
     trace(event, x1, 0, 0, 0, 0);
 }
 
-void trace2(TraceEvent event, unsigned long x1, unsigned long x2) {
+void trace2(TraceEventID event, unsigned long x1, unsigned long x2) {
     trace(event, x1, x2, 0, 0, 0);
 }
 
-void trace3(TraceEvent event, unsigned long x1, unsigned long x2, unsigned long x3) {
+void trace3(TraceEventID event, unsigned long x1, unsigned long x2, unsigned long x3) {
     trace(event, x1, x2, x3, 0, 0);
 }
 
-void trace4(TraceEvent event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4) {
+void trace4(TraceEventID event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4) {
     trace(event, x1, x2, x3, x4, 0);
 }
 
-void trace5(TraceEvent event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4, unsigned long x5) {
+void trace5(TraceEventID event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4, unsigned long x5) {
     trace(event, x1, x2, x3, x4, x5);
 }
diff --git a/tracetool b/tracetool
index 9ea9c08..0dc7f1b 100755
--- a/tracetool
+++ b/tracetool
@@ -123,13 +123,13 @@ linetoc_end_nop()
 linetoh_begin_simple()
 {
     cat <<EOF
-typedef unsigned int TraceEvent;
+typedef unsigned int TraceEventID;
 
-void trace1(TraceEvent event, unsigned long x1);
-void trace2(TraceEvent event, unsigned long x1, unsigned long x2);
-void trace3(TraceEvent event, unsigned long x1, unsigned long x2, unsigned long x3);
-void trace4(TraceEvent event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4);
-void trace5(TraceEvent event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4, unsigned long x5);
+void trace1(TraceEventID event, unsigned long x1);
+void trace2(TraceEventID event, unsigned long x1, unsigned long x2);
+void trace3(TraceEventID event, unsigned long x1, unsigned long x2, unsigned long x3);
+void trace4(TraceEventID event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4);
+void trace5(TraceEventID event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4, unsigned long x5);
 EOF
 
     simple_event_num=0
-- 
1.6.2.5



-- 
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India

[Qemu-devel] [RFC v4][PATCH 2/3] Monitor command 'info trace'

[Prerna Saxena]

Monitor command 'info trace' to display contents of trace buffer

Signed-off-by: Prerna Saxena <prerna@linux.vnet.ibm.com>
---
 configure       |    3 +++
 monitor.c       |   12 ++++++++++++
 qemu-monitor.hx |    4 ++++
 simpletrace.c   |   12 ++++++++++++
 tracetool       |    1 +
 5 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/configure b/configure
index 675d0fc..56af8dd 100755
--- a/configure
+++ b/configure
@@ -2302,6 +2302,9 @@ bsd)
 esac
 
 echo "TRACE_BACKEND=$trace_backend" >> $config_host_mak
+if test "$trace_backend" = "simple"; then
+  echo "CONFIG_SIMPLE_TRACE=y" >> $config_host_mak
+fi
 if test "$trace_backend" = "ust"; then
   LIBS="-lust $LIBS"
 fi
diff --git a/monitor.c b/monitor.c
index ad50f12..8b60830 100644
--- a/monitor.c
+++ b/monitor.c
@@ -55,6 +55,9 @@
 #include "json-streamer.h"
 #include "json-parser.h"
 #include "osdep.h"
+#ifdef CONFIG_SIMPLE_TRACE
+#include "trace.h"
+#endif
 
 //#define DEBUG
 //#define DEBUG_COMPLETION
@@ -2780,6 +2783,15 @@ static const mon_cmd_t info_cmds[] = {
         .help       = "show roms",
         .mhandler.info = do_info_roms,
     },
+#if defined(CONFIG_SIMPLE_TRACE)
+    {
+        .name       = "trace",
+        .args_type  = "",
+        .params     = "",
+        .help       = "show current contents of trace buffer",
+        .mhandler.info = do_info_trace,
+    },
+#endif
     {
         .name       = NULL,
     },
diff --git a/qemu-monitor.hx b/qemu-monitor.hx
index b6e3467..766c30f 100644
--- a/qemu-monitor.hx
+++ b/qemu-monitor.hx
@@ -114,6 +114,10 @@ show migration status
 show balloon information
 @item info qtree
 show device tree
+#ifdef CONFIG_SIMPLE_TRACE
+@item info trace
+show contents of trace buffer
+#endif
 @end table
 ETEXI
 
diff --git a/simpletrace.c b/simpletrace.c
index b488380..5734d15 100644
--- a/simpletrace.c
+++ b/simpletrace.c
@@ -1,5 +1,6 @@
 #include <stdlib.h>
 #include <stdio.h>
+#include "monitor.h"
 #include "trace.h"
 
 typedef struct {
@@ -62,3 +63,14 @@ void trace4(TraceEventID event, unsigned long x1, unsigned long x2, unsigned lon
 void trace5(TraceEventID event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4, unsigned long x5) {
     trace(event, x1, x2, x3, x4, x5);
 }
+
+void do_info_trace(Monitor *mon)
+{
+    unsigned int i;
+
+    for (i = 0; i < trace_idx ; i++) {
+        monitor_printf(mon, "Event %lu : %lx %lx %lx %lx %lx\n",
+                          trace_buf[i].event, trace_buf[i].x1, trace_buf[i].x2,
+                            trace_buf[i].x3, trace_buf[i].x4, trace_buf[i].x5);
+    }
+}
diff --git a/tracetool b/tracetool
index 0dc7f1b..6f8f8a9 100755
--- a/tracetool
+++ b/tracetool
@@ -130,6 +130,7 @@ void trace2(TraceEventID event, unsigned long x1, unsigned long x2);
 void trace3(TraceEventID event, unsigned long x1, unsigned long x2, unsigned long x3);
 void trace4(TraceEventID event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4);
 void trace5(TraceEventID event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4, unsigned long x5);
+void do_info_trace(Monitor *mon);
 EOF
 
     simple_event_num=0
-- 
1.6.2.5



-- 
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India

[Qemu-devel] [RFC v4][PATCH 3/3] Support for dynamically enabling/disabling trace events.

[Prerna Saxena]

This patch adds support for dynamically enabling/disabling of trace events.
This is done by internally maintaining each trace event's state, and 
permitting logging of data from a trace event only if it is in an 
'active' state.

Monitor commands added :
1) info trace-events 		: to view all available trace events and 
				  their state.
2) trace-event NAME on|off 	: to enable/disable data logging from a 
				  given trace event.
				  Eg, trace-event paio_submit off 
				  	disables logging of data when 
					paio_submit is hit.

By default, all trace-events are disabled. One can enable desired trace-events 
via the monitor.

Signed-off-by: Prerna Saxena <prerna@linux.vnet.ibm.com>
---
 monitor.c       |   16 ++++++++++++++++
 qemu-monitor.hx |   18 ++++++++++++++++++
 simpletrace.c   |   41 +++++++++++++++++++++++++++++++++++++++++
 tracetool       |   33 +++++++++++++++++++++++++++++----
 4 files changed, 104 insertions(+), 4 deletions(-)

diff --git a/monitor.c b/monitor.c
index 8b60830..19b1ed7 100644
--- a/monitor.c
+++ b/monitor.c
@@ -548,6 +548,15 @@ static void do_commit(Monitor *mon, const QDict *qdict)
     }
 }
 
+#ifdef CONFIG_SIMPLE_TRACE
+static void do_change_trace_event_state(Monitor *mon, const QDict *qdict)
+{
+    const char *tp_name = qdict_get_str(qdict, "name");
+    bool new_state = qdict_get_bool(qdict, "option");
+    change_trace_event_state(tp_name, new_state);
+}
+#endif
+
 static void user_monitor_complete(void *opaque, QObject *ret_data)
 {
     MonitorCompletionData *data = (MonitorCompletionData *)opaque; 
@@ -2791,6 +2800,13 @@ static const mon_cmd_t info_cmds[] = {
         .help       = "show current contents of trace buffer",
         .mhandler.info = do_info_trace,
     },
+    {
+        .name       = "trace-events",
+        .args_type  = "",
+        .params     = "",
+        .help       = "show available trace-events & their state",
+        .mhandler.info = do_info_all_trace_events,
+    },
 #endif
     {
         .name       = NULL,
diff --git a/qemu-monitor.hx b/qemu-monitor.hx
index 766c30f..0fedcf9 100644
--- a/qemu-monitor.hx
+++ b/qemu-monitor.hx
@@ -117,6 +117,8 @@ show device tree
 #ifdef CONFIG_SIMPLE_TRACE
 @item info trace
 show contents of trace buffer
+@item info trace-events
+show available trace events and their state
 #endif
 @end table
 ETEXI
@@ -225,6 +227,22 @@ STEXI
 @item logfile @var{filename}
 @findex logfile
 Output logs to @var{filename}.
+#ifdef CONFIG_SIMPLE_TRACE
+ETEXI
+
+    {
+        .name       = "trace-event",
+        .args_type  = "name:s,option:b",
+        .params     = "name on|off",
+        .help       = "changes status of a specific trace event",
+        .mhandler.cmd = do_change_trace_event_state,
+    },
+
+STEXI
+@item trace-event
+@findex trace-event
+changes status of a trace event
+#endif
 ETEXI
 
     {
diff --git a/simpletrace.c b/simpletrace.c
index 5734d15..57c41fc 100644
--- a/simpletrace.c
+++ b/simpletrace.c
@@ -24,6 +24,11 @@ static void trace(TraceEventID event, unsigned long x1,
                   unsigned long x2, unsigned long x3,
                   unsigned long x4, unsigned long x5) {
     TraceRecord *rec = &trace_buf[trace_idx];
+
+    if (!trace_list[event].state) {
+        return;
+    }
+
     rec->event = event;
     rec->x1 = x1;
     rec->x2 = x2;
@@ -74,3 +79,39 @@ void do_info_trace(Monitor *mon)
                             trace_buf[i].x3, trace_buf[i].x4, trace_buf[i].x5);
     }
 }
+
+void do_info_all_trace_events(Monitor *mon)
+{
+    unsigned int i;
+
+    for (i = 0; i < NR_TRACE_EVENTS; i++) {
+        monitor_printf(mon, "%s [Event ID %u] : state %u\n",
+                                trace_list[i].tp_name, i, trace_list[i].state);
+    }
+}
+
+static TraceEvent* find_trace_event_by_name(const char *tname)
+{
+    unsigned int i;
+
+    if (!tname) {
+        return NULL;
+    }
+
+    for (i = 0; i < NR_TRACE_EVENTS; i++) {
+        if (!strcmp(trace_list[i].tp_name, tname)) {
+            return &trace_list[i];
+        }
+    }
+    return NULL; /* indicates end of list reached without a match */
+}
+
+void change_trace_event_state(const char *tname, bool tstate)
+{
+    TraceEvent *tp;
+
+    tp = find_trace_event_by_name(tname);
+    if (tp) {
+        tp->state = tstate;
+    }
+}
diff --git a/tracetool b/tracetool
index 6f8f8a9..9e8dbd8 100755
--- a/tracetool
+++ b/tracetool
@@ -123,14 +123,23 @@ linetoc_end_nop()
 linetoh_begin_simple()
 {
     cat <<EOF
+#include <stdbool.h>
+
 typedef unsigned int TraceEventID;
 
+typedef struct {
+    const char *tp_name;
+    bool state;
+} TraceEvent;
+
 void trace1(TraceEventID event, unsigned long x1);
 void trace2(TraceEventID event, unsigned long x1, unsigned long x2);
 void trace3(TraceEventID event, unsigned long x1, unsigned long x2, unsigned long x3);
 void trace4(TraceEventID event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4);
 void trace5(TraceEventID event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4, unsigned long x5);
 void do_info_trace(Monitor *mon);
+void do_info_all_trace_events(Monitor *mon);
+void change_trace_event_state(const char *tname, bool tstate);
 EOF
 
     simple_event_num=0
@@ -163,22 +172,38 @@ EOF
 
 linetoh_end_simple()
 {
-    return
+    cat <<EOF
+#define NR_TRACE_EVENTS $simple_event_num
+extern TraceEvent trace_list[NR_TRACE_EVENTS];
+EOF
 }
 
 linetoc_begin_simple()
 {
-    return
+    cat <<EOF
+#include "trace.h"
+
+TraceEvent trace_list[] = {
+EOF
+    simple_event_num=0
+
 }
 
 linetoc_simple()
 {
-    return
+    local name
+    name=$(get_name "$1")
+    cat <<EOF
+{.tp_name = "$name", .state=0},
+EOF
+    simple_event_num=$((simple_event_num + 1))
 }
 
 linetoc_end_simple()
 {
-    return
+    cat <<EOF
+};
+EOF
 }
 
 linetoh_begin_ust()
-- 
1.6.2.5



-- 
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India

[Qemu-devel] Re: [RFC v4][PATCH 0/3] Monitor support for Qemu tracing

[Stefan Hajnoczi]

On Thu, Jun 24, 2010 at 04:49:30PM +0530, Prerna Saxena wrote:
> This set of patches enables trace visualization & control 
> via the QEMU monitor. It is based on trace infrastructure posted 
> upstream :
> ( http://lists.gnu.org/archive/html/qemu-devel/2010-05/msg02407.html )
> 
> This patchset adds monitor commands :
> - info trace : to view current contents of the trace buffer
> - info tracepoints : to view all available tracepoints and their state.
> - tracepoint NAME on|off : to enable/disable the logging of dataThis is v3 of a set of patches to enable trace visualization & control 
> via the QEMU monitor. 
> 
> Changelog from v3:
> 1. As suggested, it replaces a hash-based search of tracepoints 
> with a linear search.
> 2. Static initialization of trace event array.
> 3. Cleanups.
> 
> Changelog from v2:
> 1. Clean-ups, particularly relating to export of tdb_hash().
> 
> Changelog from v1:
> 1. Command 'info trace' is used to view current contents of buffer, in 
> place of 'trace'.
> 2. Cleanups

Applied, thanks!

http://repo.or.cz/w/qemu/stefanha.git/shortlog/refs/heads/tracing

I'd like to focus on polishing the current tracing branch into a
patchset that can be merged into QEMU.  Having this working prototype
enables us to try tracing out; we can commit fixes on top and then
squish the commits down for QEMU merge when the basic feature set is
solid.

> Todos :
> 1. Integration with QMP
> 2. More tracepoints need to be added for instrumenting other qemu components
>  such as virtio drivers, etc.

I am copying these to another email thread so we can discuss what needs
to be done to get tracing merged.

Stefan