ftrace: take advantage of variable length entries

Now that the underlining ring buffer for ftrace now hold variable length
entries, we can take advantage of this by only storing the size of the
actual event into the buffer. This happens to increase the number of
entries in the buffer dramatically.

We can also get rid of the "trace_cont" operation, but I'm keeping that
until we have no more users. Some of the ftrace tracers can now change
their code to adapt to this new feature.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 42 insertions, 39 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index f6965f775b43..e541a6b7e312 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -27,9 +27,24 @@ enum trace_type {
 };
 
 /*
+ * The trace entry - the most basic unit of tracing. This is what
+ * is printed in the end as a single line in the trace output, such as:
+ *
+ *     bash-15816 [01]   235.197585: idle_cpu <- irq_enter
+ */
+struct trace_entry {
+        unsigned char           type;
+        unsigned char           cpu;
+        unsigned char           flags;
+        unsigned char           preempt_count;
+        int                     pid;
+};
+
+/*
  * Function trace entry - function address and parent function addres:
  */
 struct ftrace_entry {
+        struct trace_entry      ent;
         unsigned long           ip;
         unsigned long           parent_ip;
 };
@@ -39,6 +54,7 @@ extern struct tracer boot_tracer;
  * Context switch trace entry - which task (and prio) we switched from/to:
  */
 struct ctx_switch_entry {
+        struct trace_entry      ent;
         unsigned int            prev_pid;
         unsigned char           prev_prio;
         unsigned char           prev_state;
@@ -52,6 +68,7 @@ struct ctx_switch_entry {
  * Special (free-form) trace entry:
  */
 struct special_entry {
+        struct trace_entry      ent;
         unsigned long           arg1;
         unsigned long           arg2;
         unsigned long           arg3;
@@ -64,6 +81,7 @@ struct special_entry {
 #define FTRACE_STACK_ENTRIES    8
 
 struct stack_entry {
+        struct trace_entry      ent;
         unsigned long           caller[FTRACE_STACK_ENTRIES];
 };
 
@@ -71,10 +89,34 @@ struct stack_entry {
  * ftrace_printk entry:
  */
 struct print_entry {
+        struct trace_entry      ent;
         unsigned long           ip;
         char                    buf[];
 };
 
+#define TRACE_OLD_SIZE          88
+
+struct trace_field_cont {
+        unsigned char           type;
+        /* Temporary till we get rid of this completely */
+        char                    buf[TRACE_OLD_SIZE - 1];
+};
+
+struct trace_mmiotrace_rw {
+        struct trace_entry      ent;
+        struct mmiotrace_rw     rw;
+};
+
+struct trace_mmiotrace_map {
+        struct trace_entry      ent;
+        struct mmiotrace_map    map;
+};
+
+struct trace_boot {
+        struct trace_entry      ent;
+        struct boot_trace       initcall;
+};
+
 /*
  * trace_flag_type is an enumeration that holds different
  * states when a trace occurs. These are:
@@ -92,46 +134,7 @@ enum trace_flag_type {
         TRACE_FLAG_CONT                 = 0x10,
 };
 
-/*
- * The trace field - the most basic unit of tracing. This is what
- * is printed in the end as a single line in the trace output, such as:
- *
- *     bash-15816 [01]   235.197585: idle_cpu <- irq_enter
- */
-struct trace_field {
-        char                    cpu;
-        char                    flags;
-        char                    preempt_count;
-        int                     pid;
-        union {
-                struct ftrace_entry             fn;
-                struct ctx_switch_entry         ctx;
-                struct special_entry            special;
-                struct stack_entry              stack;
-                struct print_entry              print;
-                struct mmiotrace_rw             mmiorw;
-                struct mmiotrace_map            mmiomap;
-                struct boot_trace               initcall;
-        };
-};
-
-struct trace_field_cont {
-        char                            buf[sizeof(struct trace_field)];
-};
-
-struct trace_entry {
-        char                            type;
-        union {
-                struct trace_field      field;
-                struct trace_field_cont cont;
-        };
-};
-
-#define TRACE_ENTRY_SIZE        sizeof(struct trace_entry)
 #define TRACE_BUF_SIZE          1024
-#define TRACE_PRINT_BUF_SIZE \
-        (sizeof(struct trace_field) - offsetof(struct trace_field, print.buf))
-#define TRACE_CONT_BUF_SIZE     sizeof(struct trace_field)
 
 /*
  * The CPU trace array - it consists of thousands of trace entries