[PATCH 18/20 -v5] mcount tracer for wakeup latency timings.

[Steven Rostedt <rostedt@goodmis.org>]

[-- Attachment #1: mcount-trace-wakeup-latency.patch --]
[-- Type: text/plain, Size: 20668 bytes --]

This patch adds hooks to trace the wake up latency of the highest
priority waking task.

  "wakeup" is added to /debugfs/tracing/available_tracers

Also added to /debugfs/tracing

  tracing_max_latency
     holds the current max latency for the wakeup

  wakeup_thresh
     if set to other than zero, a log will be recorded
     for every wakeup that takes longer than the number
     entered in here (usecs for all counters)
     (deletes previous trace)

Examples:

  (with mcount_enabled = 0)

============
preemption latency trace v1.1.5 on 2.6.24-rc8
--------------------------------------------------------------------
 latency: 26 us, #2/2, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
    -----------------
    | task: migration/0-3 (uid:0 nice:-5 policy:1 rt_prio:99)
    -----------------

                 _------=> CPU#            
                / _-----=> irqs-off        
               | / _----=> need-resched    
               || / _---=> hardirq/softirq 
               ||| / _--=> preempt-depth   
               |||| /                      
               |||||     delay             
   cmd     pid ||||| time  |   caller      
      \   /    |||||   \   |   /           
   quilt-8551  0d..3    0us+: wake_up_process+0x15/0x17 <ffffffff80233e80> (sched_exec+0xc9/0x100 <ffffffff80235343>)
   quilt-8551  0d..4   26us : sched_switch_callback+0x73/0x81 <ffffffff80338d2f> (schedule+0x483/0x6d5 <ffffffff8048b3ee>)


vim:ft=help
============

    
  (with mcount_enabled = 1)

============
preemption latency trace v1.1.5 on 2.6.24-rc8
--------------------------------------------------------------------
 latency: 36 us, #45/45, CPU#0 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
    -----------------
    | task: migration/1-5 (uid:0 nice:-5 policy:1 rt_prio:99)
    -----------------

                 _------=> CPU#            
                / _-----=> irqs-off        
               | / _----=> need-resched    
               || / _---=> hardirq/softirq 
               ||| / _--=> preempt-depth   
               |||| /                      
               |||||     delay             
   cmd     pid ||||| time  |   caller      
      \   /    |||||   \   |   /           
    bash-10653 1d..3    0us : wake_up_process+0x15/0x17 <ffffffff80233e80> (sched_exec+0xc9/0x100 <ffffffff80235343>)
    bash-10653 1d..3    1us : try_to_wake_up+0x271/0x2e7 <ffffffff80233dcf> (sub_preempt_count+0xc/0x7a <ffffffff8023309e>)
    bash-10653 1d..2    2us : try_to_wake_up+0x296/0x2e7 <ffffffff80233df4> (update_rq_clock+0x9/0x20 <ffffffff802303f3>)
    bash-10653 1d..2    2us : update_rq_clock+0x1e/0x20 <ffffffff80230408> (__update_rq_clock+0xc/0x90 <ffffffff80230366>)
    bash-10653 1d..2    3us : __update_rq_clock+0x1b/0x90 <ffffffff80230375> (sched_clock+0x9/0x29 <ffffffff80214529>)
    bash-10653 1d..2    4us : try_to_wake_up+0x2a6/0x2e7 <ffffffff80233e04> (activate_task+0xc/0x3f <ffffffff8022ffca>)
    bash-10653 1d..2    4us : activate_task+0x2d/0x3f <ffffffff8022ffeb> (enqueue_task+0xe/0x66 <ffffffff8022ff66>)
    bash-10653 1d..2    5us : enqueue_task+0x5b/0x66 <ffffffff8022ffb3> (enqueue_task_rt+0x9/0x3c <ffffffff80233351>)
    bash-10653 1d..2    6us : try_to_wake_up+0x2ba/0x2e7 <ffffffff80233e18> (check_preempt_wakeup+0x12/0x99 <ffffffff80234f84>)
[...]
    bash-10653 1d..5   33us : tracing_record_cmdline+0xcf/0xd4 <ffffffff80338aad> (_spin_unlock+0x9/0x33 <ffffffff8048d3ec>)
    bash-10653 1d..5   34us : _spin_unlock+0x19/0x33 <ffffffff8048d3fc> (sub_preempt_count+0xc/0x7a <ffffffff8023309e>)
    bash-10653 1d..4   35us : wakeup_sched_switch+0x65/0x2ff <ffffffff80339f66> (_spin_lock_irqsave+0xc/0xa9 <ffffffff8048d08b>)
    bash-10653 1d..4   35us : _spin_lock_irqsave+0x19/0xa9 <ffffffff8048d098> (add_preempt_count+0xe/0x77 <ffffffff8023311a>)
    bash-10653 1d..4   36us : sched_switch_callback+0x73/0x81 <ffffffff80338d2f> (schedule+0x483/0x6d5 <ffffffff8048b3ee>)


vim:ft=help
============

The [...] was added here to not waste your email box space.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 lib/tracing/Kconfig        |   14 +
 lib/tracing/Makefile       |    1 
 lib/tracing/trace_wakeup.c |  333 +++++++++++++++++++++++++++++++++++++++++++++
 lib/tracing/tracer.c       |  131 +++++++++++++++++
 lib/tracing/tracer.h       |    6 
 5 files changed, 483 insertions(+), 2 deletions(-)

Index: linux-mcount.git/lib/tracing/Kconfig
===================================================================
--- linux-mcount.git.orig/lib/tracing/Kconfig	2008-01-23 10:27:39.000000000 -0500
+++ linux-mcount.git/lib/tracing/Kconfig	2008-01-23 10:27:49.000000000 -0500
@@ -9,6 +9,9 @@ config MCOUNT
 	bool
 	select FRAME_POINTER
 
+config TRACER_MAX_TRACE
+	bool
+
 config TRACING
         bool
 	select DEBUG_FS
@@ -25,6 +28,17 @@ config FUNCTION_TRACER
 	  that the debugging mechanism using this facility will hook by
 	  providing a set of inline routines.
 
+config WAKEUP_TRACER
+	bool "Trace wakeup latencies"
+	depends on DEBUG_KERNEL
+	select TRACING
+	select CONTEXT_SWITCH_TRACER
+	select TRACER_MAX_TRACE
+	help
+	  This tracer adds hooks into scheduling to time the latency
+	  of the highest priority task tasks to be scheduled in
+	  after it has worken up.
+
 config CONTEXT_SWITCH_TRACER
 	bool "Trace process context switches"
 	depends on DEBUG_KERNEL
Index: linux-mcount.git/lib/tracing/Makefile
===================================================================
--- linux-mcount.git.orig/lib/tracing/Makefile	2008-01-23 10:27:31.000000000 -0500
+++ linux-mcount.git/lib/tracing/Makefile	2008-01-23 10:27:49.000000000 -0500
@@ -3,5 +3,6 @@ obj-$(CONFIG_MCOUNT) += libmcount.o
 obj-$(CONFIG_TRACING) += tracer.o
 obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o
 obj-$(CONFIG_FUNCTION_TRACER) += trace_function.o
+obj-$(CONFIG_WAKEUP_TRACER) += trace_wakeup.o
 
 libmcount-y := mcount.o
Index: linux-mcount.git/lib/tracing/trace_wakeup.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-mcount.git/lib/tracing/trace_wakeup.c	2008-01-23 10:27:49.000000000 -0500
@@ -0,0 +1,333 @@
+/*
+ * trace task wakeup timings
+ *
+ * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
+ *
+ * Based on code from the latency_tracer, that is:
+ *
+ *  Copyright (C) 2004-2006 Ingo Molnar
+ *  Copyright (C) 2004 William Lee Irwin III
+ */
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <linux/kallsyms.h>
+#include <linux/uaccess.h>
+#include <linux/mcount.h>
+
+#include "tracer.h"
+
+static struct tracing_trace *tracer_trace __read_mostly;
+static int trace_enabled __read_mostly;
+
+static struct task_struct *wakeup_task;
+static int wakeup_cpu;
+static unsigned wakeup_prio = -1;
+
+static DEFINE_SPINLOCK(wakeup_lock);
+
+static void notrace __wakeup_reset(struct tracing_trace *tr);
+/*
+ * Should this new latency be reported/recorded?
+ */
+static int notrace report_latency(cycle_t delta)
+{
+	if (tracing_thresh) {
+		if (delta < tracing_thresh)
+			return 0;
+	} else {
+		if (delta <= tracing_max_latency)
+			return 0;
+	}
+	return 1;
+}
+
+static void notrace wakeup_sched_switch(void *private,
+					struct task_struct *prev,
+					struct task_struct *next)
+{
+	struct tracing_trace **ptr = private;
+	struct tracing_trace *tr = *ptr;
+	struct tracing_trace_cpu *data;
+	unsigned long latency = 0, t0 = 0, t1 = 0;
+	cycle_t T0, T1, delta;
+	unsigned long flags;
+	int cpu;
+
+	if (unlikely(!trace_enabled) || next != wakeup_task)
+		return;
+
+	/* The task we are waitng for is waking up */
+	data = tr->data[wakeup_cpu];
+
+	if (unlikely(!data) || unlikely(!data->trace) ||
+	    unlikely(atomic_read(&data->disabled)))
+		return;
+
+	spin_lock_irqsave(&wakeup_lock, flags);
+
+	/* disable local data, not wakeup_cpu data */
+	cpu = raw_smp_processor_id();
+	atomic_inc(&tr->data[cpu]->disabled);
+
+	/* We could race with grabbing wakeup_lock */
+	if (unlikely(!trace_enabled || next != wakeup_task))
+		goto out;
+
+	tracing_function_trace(tr, data, CALLER_ADDR1, CALLER_ADDR2, flags);
+
+	/*
+	 * usecs conversion is slow so we try to delay the conversion
+	 * as long as possible:
+	 */
+	T0 = data->preempt_timestamp;
+	T1 = now();
+	delta = T1-T0;
+
+	if (!report_latency(delta))
+		goto out;
+
+	latency = cycles_to_usecs(delta);
+
+	tracing_max_latency = delta;
+	t0 = cycles_to_usecs(T0);
+	t1 = cycles_to_usecs(T1);
+
+	update_max_tr(tr, wakeup_task, wakeup_cpu);
+
+	if (tracing_thresh)
+		printk(KERN_WARNING "(%16s-%-5d|#%d): %lu us wakeup latency "
+		       "violates %lu us threshold.\n"
+		       " => started at timestamp %lu: ",
+				wakeup_task->comm, wakeup_task->pid,
+				raw_smp_processor_id(),
+				latency, cycles_to_usecs(tracing_thresh), t0);
+	else
+		printk(KERN_WARNING "(%16s-%-5d|#%d): new %lu us maximum "
+		       "wakeup latency.\n => started at timestamp %lu: ",
+				wakeup_task->comm, wakeup_task->pid,
+				cpu, latency, t0);
+
+	printk(KERN_CONT "   ended at timestamp %lu: ", t1);
+	dump_stack();
+	t1 = cycles_to_usecs(now());
+	printk(KERN_CONT "   dump-end timestamp %lu\n\n", t1);
+
+out:
+	__wakeup_reset(tr);
+	atomic_dec(&tr->data[cpu]->disabled);
+	spin_unlock_irqrestore(&wakeup_lock, flags);
+
+}
+
+static struct tracer_switch_ops switch_ops __read_mostly = {
+	.func = wakeup_sched_switch,
+	.private = &tracer_trace,
+};
+
+static void notrace __wakeup_reset(struct tracing_trace *tr)
+{
+	struct tracing_trace_cpu *data;
+	int cpu;
+
+	assert_spin_locked(&wakeup_lock);
+
+	for_each_possible_cpu(cpu) {
+		data = tr->data[cpu];
+		tracing_reset(data);
+	}
+
+	wakeup_cpu = -1;
+	wakeup_prio = -1;
+	if (wakeup_task) {
+		put_task_struct(wakeup_task);
+		atomic_dec(&trace_record_cmdline);
+		tracing_stop_function_trace();
+		unregister_tracer_switch(&switch_ops);
+	}
+
+	wakeup_task = NULL;
+
+	/*
+	 * Don't let the trace_enabled = 1 show up before
+	 * the wakeup_task is reset.
+	 */
+	smp_wmb();
+}
+
+static void notrace wakeup_reset(struct tracing_trace *tr)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&wakeup_lock, flags);
+	__wakeup_reset(tr);
+	spin_unlock_irqrestore(&wakeup_lock, flags);
+}
+
+static notrace void wakeup_check_start(struct tracing_trace *tr,
+				       struct task_struct *p,
+				       struct task_struct *curr)
+{
+	unsigned long flags;
+	int cpu = smp_processor_id();
+
+	if (likely(!rt_task(p)) ||
+	    p->prio >= wakeup_prio ||
+	    p->prio >= curr->prio)
+		return;
+
+	atomic_inc(&tr->data[cpu]->disabled);
+	if (unlikely(atomic_read(&tr->data[cpu]->disabled) != 1))
+		goto out;
+
+	/* interrupts should be off from try_to_wake_up */
+	spin_lock(&wakeup_lock);
+
+	/* check for races. */
+	if (!trace_enabled || p->prio >= wakeup_prio)
+		goto out_locked;
+
+	/* reset the trace */
+	__wakeup_reset(tr);
+
+	wakeup_cpu = task_cpu(p);
+	wakeup_prio = p->prio;
+
+	wakeup_task = p;
+	get_task_struct(wakeup_task);
+	register_tracer_switch(&switch_ops);
+	tracing_start_function_trace();
+	atomic_inc(&trace_record_cmdline);
+
+	tr->data[wakeup_cpu]->preempt_timestamp = now();
+
+	local_save_flags(flags);
+	tracing_function_trace(tr, tr->data[wakeup_cpu],
+			       CALLER_ADDR1, CALLER_ADDR2, flags);
+
+
+ out_locked:
+	spin_unlock(&wakeup_lock);
+ out:
+	atomic_dec(&tr->data[cpu]->disabled);
+}
+
+static notrace void wake_up_callback(const struct marker *mdata,
+				     void *private_data,
+				     const char *format, ...)
+{
+	struct tracing_trace **ptr = mdata->private;
+	struct tracing_trace *tr = *ptr;
+	struct task_struct *curr;
+	struct task_struct *p;
+	va_list ap;
+
+	if (likely(!trace_enabled))
+		return;
+
+	va_start(ap, format);
+
+	/* now get the meat: "p %p rq->curr %p" */
+	p = va_arg(ap, typeof(p));
+	curr = va_arg(ap, typeof(curr));
+
+	va_end(ap);
+
+	wakeup_check_start(tr, p, curr);
+}
+
+static notrace void start_wakeup_trace(struct tracing_trace *tr)
+{
+	wakeup_reset(tr);
+	trace_enabled = 1;
+}
+
+static notrace void stop_wakeup_trace(struct tracing_trace *tr)
+{
+	trace_enabled = 0;
+}
+
+static notrace void wakeup_trace_init(struct tracing_trace *tr)
+{
+	tracer_trace = tr;
+
+	if (tr->ctrl)
+		start_wakeup_trace(tr);
+}
+
+static notrace void wakeup_trace_reset(struct tracing_trace *tr)
+{
+	if (tr->ctrl) {
+		stop_wakeup_trace(tr);
+		/* make sure we put back any tasks we are tracing */
+		wakeup_reset(tr);
+	}
+}
+
+static void wakeup_trace_ctrl_update(struct tracing_trace *tr)
+{
+	if (tr->ctrl)
+		start_wakeup_trace(tr);
+	else
+		stop_wakeup_trace(tr);
+}
+
+static void notrace wakeup_trace_open(struct tracing_iterator *iter)
+{
+	/* stop the trace while dumping */
+	if (iter->tr->ctrl)
+		stop_wakeup_trace(iter->tr);
+}
+
+static void notrace wakeup_trace_close(struct tracing_iterator *iter)
+{
+	/* forget about any processes we were recording */
+	if (iter->tr->ctrl)
+		start_wakeup_trace(iter->tr);
+}
+
+static struct trace_types_struct wakeup_trace __read_mostly =
+{
+	.name = "wakeup",
+	.init = wakeup_trace_init,
+	.reset = wakeup_trace_reset,
+	.open = wakeup_trace_open,
+	.close = wakeup_trace_close,
+	.ctrl_update = wakeup_trace_ctrl_update,
+	.print_max = 1,
+};
+
+__init static int init_wakeup_trace(void)
+{
+	int ret;
+
+	ret = register_trace(&wakeup_trace);
+	if (ret)
+		return ret;
+
+	ret = marker_probe_register("kernel_sched_wakeup",
+				    "p %p rq->curr %p",
+				    wake_up_callback,
+				    &tracer_trace);
+	if (ret) {
+		pr_info("wakeup trace: Couldn't add marker"
+			" probe to kernel_sched_wakeup\n");
+		goto fail;
+	}
+
+	ret = marker_arm("kernel_sched_wakeup");
+	if (ret) {
+		pr_info("wakeup trace: Couldn't arm probe"
+			" kernel_sched_wakeup\n");
+		goto fail_deprobe;
+	}
+
+	return 0;
+ fail_deprobe:
+	marker_probe_unregister("kernel_sched_wakeup");
+ fail:
+	unregister_trace(&wakeup_trace);
+	return 0;
+}
+
+device_initcall(init_wakeup_trace);
Index: linux-mcount.git/lib/tracing/tracer.c
===================================================================
--- linux-mcount.git.orig/lib/tracing/tracer.c	2008-01-23 10:27:39.000000000 -0500
+++ linux-mcount.git/lib/tracing/tracer.c	2008-01-23 10:27:49.000000000 -0500
@@ -28,8 +28,13 @@
 
 #include "tracer.h"
 
+unsigned long tracing_max_latency __read_mostly = (cycle_t)ULONG_MAX;
+unsigned long tracing_thresh __read_mostly;
+
 static struct tracing_trace tracer_trace __read_mostly;
 static DEFINE_PER_CPU(struct tracing_trace_cpu, tracer_trace_cpu);
+static struct tracing_trace max_tr __read_mostly;
+static DEFINE_PER_CPU(struct tracing_trace_cpu, max_data);
 static int trace_enabled __read_mostly;
 static unsigned long trace_nr_entries = (65536UL);
 
@@ -64,6 +69,43 @@ enum trace_flag_type {
 	TRACE_FLAG_SOFTIRQ		= 0x08,
 };
 
+/*
+ * Copy the new maximum trace into the separate maximum-trace
+ * structure. (this way the maximum trace is permanently saved,
+ * for later retrieval via /debugfs/tracing/latency_trace)
+ */
+void update_max_tr(struct tracing_trace *tr, struct task_struct *tsk, int cpu)
+{
+	struct tracing_trace_cpu *data = tr->data[cpu];
+	void *save_trace;
+	int i;
+
+	max_tr.cpu = cpu;
+	max_tr.time_start = data->preempt_timestamp;
+
+
+	/* clear out all the previous traces */
+	for_each_possible_cpu(i) {
+		data = tr->data[i];
+		save_trace = max_tr.data[i]->trace;
+		memcpy(max_tr.data[i], data, sizeof(*data));
+		data->trace = save_trace;
+	}
+
+	data = max_tr.data[cpu];
+	data->saved_latency = tracing_max_latency;
+
+	memcpy(data->comm, tsk->comm, TASK_COMM_LEN);
+	data->pid = tsk->pid;
+	data->uid = tsk->uid;
+	data->nice = tsk->static_prio - 20 - MAX_RT_PRIO;
+	data->policy = tsk->policy;
+	data->rt_priority = tsk->rt_priority;
+
+	/* record this tasks comm */
+	tracing_record_cmdline(current);
+}
+
 int register_trace(struct trace_types_struct *type)
 {
 	struct trace_types_struct *t;
@@ -797,9 +839,14 @@ __tracing_open(struct inode *inode, stru
 		goto out;
 	}
 
-	iter->tr = inode->i_private;
+	mutex_lock(&trace_types_lock);
+	if (current_trace && current_trace->print_max)
+		iter->tr = &max_tr;
+	else
+		iter->tr = inode->i_private;
 	iter->trace = current_trace;
 	iter->pos = -1;
+	mutex_unlock(&trace_types_lock);
 
 	/* TODO stop tracer */
 	*ret = seq_open(file, &tracer_seq_ops);
@@ -1079,7 +1126,7 @@ static ssize_t tracing_ctrl_write(struct
 		tr->ctrl = val;
 
 		mutex_lock(&trace_types_lock);
-		if (current_trace->ctrl_update)
+		if (current_trace && current_trace->ctrl_update)
 			current_trace->ctrl_update(tr);
 		mutex_unlock(&trace_types_lock);
 	}
@@ -1150,6 +1197,50 @@ static ssize_t tracing_set_trace_write(s
 	return cnt;
 }
 
+static ssize_t tracing_max_lat_read(struct file *filp, char __user *ubuf,
+				    size_t cnt, loff_t *ppos)
+{
+	unsigned long *ptr = filp->private_data;
+	char buf[64];
+	int r;
+
+	r = snprintf(buf, 64, "%ld\n",
+		     *ptr == (unsigned long)-1 ? -1 : cycles_to_usecs(*ptr));
+	if (r > 64)
+		r = 64;
+	return simple_read_from_buffer(ubuf, cnt, ppos,
+				       buf, r);
+}
+
+static ssize_t tracing_max_lat_write(struct file *filp,
+				     const char __user *ubuf,
+				     size_t cnt, loff_t *ppos)
+{
+	long *ptr = filp->private_data;
+	long val;
+	char buf[64];
+
+	if (cnt > 63)
+		cnt = 63;
+
+	if (copy_from_user(&buf, ubuf, cnt))
+		return -EFAULT;
+
+	buf[cnt] = 0;
+
+	val = simple_strtoul(buf, NULL, 10);
+
+	*ptr = usecs_to_cycles(val);
+
+	return cnt;
+}
+
+static struct file_operations tracing_max_lat_fops = {
+	.open = tracing_open_generic,
+	.read = tracing_max_lat_read,
+	.write = tracing_max_lat_write,
+};
+
 static struct file_operations tracing_ctrl_fops = {
 	.open = tracing_open_generic,
 	.read = tracing_ctrl_read,
@@ -1218,6 +1309,19 @@ static __init void tracer_init_debugfs(v
 				    &tracer_trace, &set_tracer_fops);
 	if (!entry)
 		pr_warning("Could not create debugfs 'trace' entry\n");
+
+	entry = debugfs_create_file("tracing_max_latency", 0644, d_tracer,
+				    &tracing_max_latency,
+				    &tracing_max_lat_fops);
+	if (!entry)
+		pr_warning("Could not create debugfs "
+			   "'tracing_max_latency' entry\n");
+
+	entry = debugfs_create_file("tracing_thresh", 0644, d_tracer,
+				    &tracing_thresh, &tracing_max_lat_fops);
+	if (!entry)
+		pr_warning("Could not create debugfs "
+			   "'tracing_threash' entry\n");
 }
 
 static inline notrace int page_order(const unsigned long size)
@@ -1235,6 +1339,8 @@ __init static int tracer_alloc_buffers(v
 
 	for_each_possible_cpu(i) {
 		tracer_trace.data[i] = &per_cpu(tracer_trace_cpu, i);
+		max_tr.data[i] = &per_cpu(max_data, i);
+
 		array = (struct tracing_entry *)
 			  __get_free_pages(GFP_KERNEL, order);
 		if (array == NULL) {
@@ -1243,6 +1349,18 @@ __init static int tracer_alloc_buffers(v
 			goto free_buffers;
 		}
 		tracer_trace.data[i]->trace = array;
+
+/* Only allocate if we are actually using the max trace */
+#ifdef CONFIG_TRACER_MAX_TRACE
+		array = (struct tracing_entry *)
+			  __get_free_pages(GFP_KERNEL, order);
+		if (array == NULL) {
+			printk(KERN_ERR "wakeup tracer: failed to allocate"
+			       " %ld bytes for trace buffer!\n", size);
+			goto free_buffers;
+		}
+		max_tr.data[i]->trace = array;
+#endif
 	}
 
 	/*
@@ -1250,6 +1368,7 @@ __init static int tracer_alloc_buffers(v
 	 * round up a bit.
 	 */
 	tracer_trace.entries = size / TRACING_ENTRY_SIZE;
+	max_tr.entries = tracer_trace.entries;
 
 	pr_info("tracer: %ld bytes allocated for %ld",
 		size, trace_nr_entries);
@@ -1270,6 +1389,14 @@ __init static int tracer_alloc_buffers(v
 			free_pages((unsigned long)data->trace, order);
 			data->trace = NULL;
 		}
+
+#ifdef CONFIG_TRACER_MAX_TRACE
+		data = max_tr.data[i];
+		if (data && data->trace) {
+			free_pages((unsigned long)data->trace, order);
+			data->trace = NULL;
+		}
+#endif
 	}
 	return -ENOMEM;
 }
Index: linux-mcount.git/lib/tracing/tracer.h
===================================================================
--- linux-mcount.git.orig/lib/tracing/tracer.h	2008-01-23 10:27:42.000000000 -0500
+++ linux-mcount.git/lib/tracing/tracer.h	2008-01-23 10:27:49.000000000 -0500
@@ -69,6 +69,7 @@ struct trace_types_struct {
 	void (*stop)(struct tracing_iterator *iter);
 	void (*ctrl_update)(struct tracing_trace *tr);
 	struct trace_types_struct *next;
+	int print_max;
 };
 
 struct tracing_iterator {
@@ -107,6 +108,11 @@ void unregister_trace(struct trace_types
 extern atomic_t trace_record_cmdline;
 extern atomic_t trace_record_cmdline_disabled;
 
+extern unsigned long tracing_max_latency;
+extern unsigned long tracing_thresh;
+
+void update_max_tr(struct tracing_trace *tr, struct task_struct *tsk, int cpu);
+
 static inline notrace cycle_t now(void)
 {
 	return get_monotonic_cycles();

--