[RFC patch 24/41] Linux Kernel Markers - Use Immediate Values

[Mathieu Desnoyers]

Make markers use immediate values.

Changelog :
- Use imv_* instead of immediate_*.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
---
 Documentation/markers.txt |   17 +++++++++++++----
 include/linux/marker.h    |   16 ++++++++++++----
 kernel/marker.c           |   12 ++++++++----
 ltt/ltt-marker-control.c  |    4 ++--
 4 files changed, 35 insertions(+), 14 deletions(-)

Index: linux-2.6-lttng/include/linux/marker.h
===================================================================
--- linux-2.6-lttng.orig/include/linux/marker.h	2009-02-06 15:03:19.000000000 -0500
+++ linux-2.6-lttng/include/linux/marker.h	2009-02-06 15:17:46.000000000 -0500
@@ -14,6 +14,7 @@
 
 #include <stdarg.h>
 #include <linux/types.h>
+#include <linux/immediate.h>
 
 struct module;
 struct marker;
@@ -43,7 +44,7 @@ struct marker {
 	const char *format;	/* Marker format string, describing the
 				 * variable argument list.
 				 */
-	char state;		/* Marker state. */
+	DEFINE_IMV(char, state);/* Immediate value state. */
 	char ptype;		/* probe type : 0 : single, 1 : multi */
 				/* Probe wrapper */
 	void (*call)(const struct marker *mdata, void *call_private, ...);
@@ -86,9 +87,16 @@ struct marker {
 	do {								\
 		DEFINE_MARKER(name, format);				\
 		__mark_check_format(format, ## args);			\
-		if (unlikely(__mark_##name.state)) {			\
-			(*__mark_##name.call)				\
-				(&__mark_##name, call_private, ## args);\
+		if (!generic) {						\
+			if (unlikely(imv_read(__mark_##name.state)))	\
+				(*__mark_##name.call)			\
+					(&__mark_##name, call_private,	\
+					## args);			\
+		} else {						\
+			if (unlikely(_imv_read(__mark_##name.state)))	\
+				(*__mark_##name.call)			\
+					(&__mark_##name, call_private,	\
+					## args);			\
 		}							\
 	} while (0)
 
Index: linux-2.6-lttng/kernel/marker.c
===================================================================
--- linux-2.6-lttng.orig/kernel/marker.c	2009-02-06 15:03:19.000000000 -0500
+++ linux-2.6-lttng/kernel/marker.c	2009-02-06 15:17:46.000000000 -0500
@@ -24,6 +24,7 @@
 #include <linux/marker.h>
 #include <linux/err.h>
 #include <linux/slab.h>
+#include <linux/immediate.h>
 
 extern struct marker __start___markers[];
 extern struct marker __stop___markers[];
@@ -532,7 +533,7 @@ static int set_marker(struct marker_entr
 	smp_wmb();
 	elem->ptype = entry->ptype;
 
-	if (elem->tp_name && (active ^ elem->state)) {
+	if (elem->tp_name && (active ^ _imv_read(elem->state))) {
 		WARN_ON(!elem->tp_cb);
 		/*
 		 * It is ok to directly call the probe registration because type
@@ -562,7 +563,7 @@ static int set_marker(struct marker_entr
 				(unsigned long)elem->tp_cb));
 		}
 	}
-	elem->state = active;
+	elem->state__imv = active;
 
 	return ret;
 }
@@ -578,7 +579,7 @@ static void disable_marker(struct marker
 	int ret;
 
 	/* leave "call" as is. It is known statically. */
-	if (elem->tp_name && elem->state) {
+	if (elem->tp_name && _imv_read(elem->state)) {
 		WARN_ON(!elem->tp_cb);
 		/*
 		 * It is ok to directly call the probe registration because type
@@ -593,7 +594,7 @@ static void disable_marker(struct marker
 		 */
 		module_put(__module_text_address((unsigned long)elem->tp_cb));
 	}
-	elem->state = 0;
+	elem->state__imv = 0;
 	elem->single.func = __mark_empty_function;
 	/* Update the function before setting the ptype */
 	smp_wmb();
@@ -657,6 +658,9 @@ static void marker_update_probes(void)
 	/* Markers in modules. */
 	module_update_markers();
 	tracepoint_probe_update_all();
+	/* Update immediate values */
+	core_imv_update();
+	module_imv_update();
 }
 
 /**
Index: linux-2.6-lttng/Documentation/markers.txt
===================================================================
--- linux-2.6-lttng.orig/Documentation/markers.txt	2009-02-06 14:45:26.000000000 -0500
+++ linux-2.6-lttng/Documentation/markers.txt	2009-02-06 15:17:46.000000000 -0500
@@ -15,10 +15,12 @@ provide at runtime. A marker can be "on"
 (no probe is attached). When a marker is "off" it has no effect, except for
 adding a tiny time penalty (checking a condition for a branch) and space
 penalty (adding a few bytes for the function call at the end of the
-instrumented function and adds a data structure in a separate section).  When a
-marker is "on", the function you provide is called each time the marker is
-executed, in the execution context of the caller. When the function provided
-ends its execution, it returns to the caller (continuing from the marker site).
+instrumented function and adds a data structure in a separate section). The
+immediate values are used to minimize the impact on data cache, encoding the
+condition in the instruction stream. When a marker is "on", the function you
+provide is called each time the marker is executed, in the execution context of
+the caller. When the function provided ends its execution, it returns to the
+caller (continuing from the marker site).
 
 You can put markers at important locations in the code. Markers are
 lightweight hooks that can pass an arbitrary number of parameters,
@@ -90,6 +92,13 @@ notrace void probe_tracepoint_name(unsig
 	/* write data to trace buffers ... */
 }
 
+* Optimization for a given architecture
+
+To force use of a non-optimized version of the markers, _trace_mark() should be
+used. It takes the same parameters as the normal markers, but it does not use
+the immediate values based on code patching.
+
+
 * Probe / marker example
 
 See the example provided in samples/markers/src

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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