diff --git a/arch/Kconfig b/arch/Kconfig
index 99193b1..beea3cc 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -30,6 +30,18 @@
 
 	  If unsure, say N.
 
+config OPROFILE_EVENT_MULTIPLEX
+	bool "OProfile multiplexing support (EXPERIMENTAL)"
+	default n
+	depends on OPROFILE && X86
+	help
+	  The number of hardware counters is limited. The multiplexing
+	  feature enables OProfile to gather more events than counters
+	  are provided by the hardware. This is realized by switching
+	  between events at an user specified time interval.
+
+	  If unsure, say N.
+
 config HAVE_OPROFILE
 	bool
 
diff --git a/arch/x86/oprofile/nmi_int.c b/arch/x86/oprofile/nmi_int.c
index fca8dc9..e54f6a0 100644
--- a/arch/x86/oprofile/nmi_int.c
+++ b/arch/x86/oprofile/nmi_int.c
@@ -1,11 +1,14 @@
 /**
  * @file nmi_int.c
  *
- * @remark Copyright 2002-2008 OProfile authors
+ * @remark Copyright 2002-2009 OProfile authors
  * @remark Read the file COPYING
  *
  * @author John Levon <levon@movementarian.org>
  * @author Robert Richter <robert.richter@amd.com>
+ * @author Barry Kasindorf <barry.kasindorf@amd.com>
+ * @author Jason Yeh <jason.yeh@amd.com>
+ * @author Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
  */
 
 #include <linux/init.h>
@@ -24,6 +27,12 @@
 #include "op_counter.h"
 #include "op_x86_model.h"
 
+
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+DEFINE_PER_CPU(int, switch_index);
+#endif
+
+
 static struct op_x86_model_spec const *model;
 static DEFINE_PER_CPU(struct op_msrs, cpu_msrs);
 static DEFINE_PER_CPU(unsigned long, saved_lvtpc);
@@ -31,6 +40,13 @@
 /* 0 == registered but off, 1 == registered and on */
 static int nmi_enabled = 0;
 
+
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+extern atomic_t multiplex_counter;
+#endif
+
+struct op_counter_config counter_config[OP_MAX_COUNTER];
+
 /* common functions */
 
 u64 op_x86_get_ctrl(struct op_x86_model_spec const *model,
@@ -95,6 +111,11 @@
 		per_cpu(cpu_msrs, i).counters = NULL;
 		kfree(per_cpu(cpu_msrs, i).controls);
 		per_cpu(cpu_msrs, i).controls = NULL;
+
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+		kfree(per_cpu(cpu_msrs, i).multiplex);
+		per_cpu(cpu_msrs, i).multiplex = NULL;
+#endif
 	}
 }
 
@@ -103,6 +124,9 @@
 	int success = 1;
 	size_t controls_size = sizeof(struct op_msr) * model->num_controls;
 	size_t counters_size = sizeof(struct op_msr) * model->num_counters;
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	size_t multiplex_size = sizeof(struct op_msr) * model->num_virt_counters;
+#endif
 
 	int i;
 	for_each_possible_cpu(i) {
@@ -118,6 +142,14 @@
 			success = 0;
 			break;
 		}
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+		per_cpu(cpu_msrs, i).multiplex =
+				kmalloc(multiplex_size, GFP_KERNEL);
+		if (!per_cpu(cpu_msrs, i).multiplex) {
+			success = 0;
+			break;
+		}
+#endif
 	}
 
 	if (!success)
@@ -126,6 +158,25 @@
 	return success;
 }
 
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+
+static void nmi_setup_cpu_mux(struct op_msrs const * const msrs)
+{
+	int i;
+	struct op_msr *multiplex = msrs->multiplex;
+
+	for (i = 0; i < model->num_virt_counters; ++i) {
+		if (counter_config[i].enabled) {
+			multiplex[i].saved = -(u64)counter_config[i].count;
+		} else {
+			multiplex[i].addr  = 0;
+			multiplex[i].saved = 0;
+		}
+	}
+}
+
+#endif
+
 static void nmi_cpu_setup(void *dummy)
 {
 	int cpu = smp_processor_id();
@@ -133,6 +184,9 @@
 	nmi_cpu_save_registers(msrs);
 	spin_lock(&oprofilefs_lock);
 	model->setup_ctrs(model, msrs);
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	nmi_setup_cpu_mux(msrs);
+#endif
 	spin_unlock(&oprofilefs_lock);
 	per_cpu(saved_lvtpc, cpu) = apic_read(APIC_LVTPC);
 	apic_write(APIC_LVTPC, APIC_DM_NMI);
@@ -173,14 +227,52 @@
 			memcpy(per_cpu(cpu_msrs, cpu).controls,
 				per_cpu(cpu_msrs, 0).controls,
 				sizeof(struct op_msr) * model->num_controls);
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+			memcpy(per_cpu(cpu_msrs, cpu).multiplex,
+				per_cpu(cpu_msrs, 0).multiplex,
+				sizeof(struct op_msr) * model->num_virt_counters);
+#endif
 		}
-
 	}
 	on_each_cpu(nmi_cpu_setup, NULL, 1);
 	nmi_enabled = 1;
 	return 0;
 }
 
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+
+static void nmi_cpu_save_mpx_registers(struct op_msrs *msrs)
+{
+	unsigned int si = __get_cpu_var(switch_index);
+	struct op_msr *multiplex = msrs->multiplex;
+	unsigned int i;
+
+	for (i = 0; i < model->num_counters; ++i) {
+		int offset = i + si;
+		if (multiplex[offset].addr) {
+			rdmsrl(multiplex[offset].addr,
+			       multiplex[offset].saved);
+		}
+	}
+}
+
+static void nmi_cpu_restore_mpx_registers(struct op_msrs *msrs)
+{
+	unsigned int si = __get_cpu_var(switch_index);
+	struct op_msr *multiplex = msrs->multiplex;
+	unsigned int i;
+
+	for (i = 0; i < model->num_counters; ++i) {
+		int offset = i + si;
+		if (multiplex[offset].addr) {
+			wrmsrl(multiplex[offset].addr,
+			       multiplex[offset].saved);
+		}
+	}
+}
+
+#endif
+
 static void nmi_cpu_restore_registers(struct op_msrs *msrs)
 {
 	struct op_msr *counters = msrs->counters;
@@ -214,6 +306,9 @@
 	apic_write(APIC_LVTPC, per_cpu(saved_lvtpc, cpu));
 	apic_write(APIC_LVTERR, v);
 	nmi_cpu_restore_registers(msrs);
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	__get_cpu_var(switch_index) = 0;
+#endif
 }
 
 static void nmi_shutdown(void)
@@ -252,16 +347,15 @@
 	on_each_cpu(nmi_cpu_stop, NULL, 1);
 }
 
-struct op_counter_config counter_config[OP_MAX_COUNTER];
-
 static int nmi_create_files(struct super_block *sb, struct dentry *root)
 {
 	unsigned int i;
 
-	for (i = 0; i < model->num_counters; ++i) {
+	for (i = 0; i < model->num_virt_counters; ++i) {
 		struct dentry *dir;
 		char buf[4];
 
+#ifndef CONFIG_OPROFILE_EVENT_MULTIPLEX
 		/* quick little hack to _not_ expose a counter if it is not
 		 * available for use.  This should protect userspace app.
 		 * NOTE:  assumes 1:1 mapping here (that counters are organized
@@ -269,6 +363,7 @@
 		 */
 		if (unlikely(!avail_to_resrv_perfctr_nmi_bit(i)))
 			continue;
+#endif /* CONFIG_OPROFILE_EVENT_MULTIPLEX */
 
 		snprintf(buf,  sizeof(buf), "%d", i);
 		dir = oprofilefs_mkdir(sb, root, buf);
@@ -283,6 +378,57 @@
 	return 0;
 }
 
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+
+static void nmi_cpu_switch(void *dummy)
+{
+	int cpu = smp_processor_id();
+	int si = per_cpu(switch_index, cpu);
+	struct op_msrs *msrs = &per_cpu(cpu_msrs, cpu);
+
+	nmi_cpu_stop(NULL);
+	nmi_cpu_save_mpx_registers(msrs);
+
+	/* move to next set */
+	si += model->num_counters;
+	if ((si > model->num_virt_counters) || (counter_config[si].count == 0))
+		per_cpu(switch_index, cpu) = 0;
+	else
+		per_cpu(switch_index, cpu) = si;
+
+	model->switch_ctrl(model, msrs);
+	nmi_cpu_restore_mpx_registers(msrs);
+
+	nmi_cpu_start(NULL);
+}
+
+
+/*
+ * Quick check to see if multiplexing is necessary.
+ * The check should be sufficient since counters are used
+ * in ordre.
+ */
+static int nmi_multiplex_on(void)
+{
+	return counter_config[model->num_counters].count ? 0 : -EINVAL;
+}
+
+static int nmi_switch_event(void)
+{
+	if (!model->switch_ctrl)
+		return -ENOSYS;		/* not implemented */
+	if (nmi_multiplex_on() < 0)
+		return -EINVAL;		/* not necessary */
+
+	on_each_cpu(nmi_cpu_switch, NULL, 1);
+
+	atomic_inc(&multiplex_counter);
+
+	return 0;
+}
+
+#endif
+
 #ifdef CONFIG_SMP
 static int oprofile_cpu_notifier(struct notifier_block *b, unsigned long action,
 				 void *data)
@@ -516,12 +662,18 @@
 	register_cpu_notifier(&oprofile_cpu_nb);
 #endif
 	/* default values, can be overwritten by model */
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	__raw_get_cpu_var(switch_index) = 0;
+#endif
 	ops->create_files	= nmi_create_files;
 	ops->setup		= nmi_setup;
 	ops->shutdown		= nmi_shutdown;
 	ops->start		= nmi_start;
 	ops->stop		= nmi_stop;
 	ops->cpu_type		= cpu_type;
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	ops->switch_events	= nmi_switch_event;
+#endif
 
 	if (model->init)
 		ret = model->init(ops);
diff --git a/arch/x86/oprofile/op_counter.h b/arch/x86/oprofile/op_counter.h
index 91b6a11..e28398d 100644
--- a/arch/x86/oprofile/op_counter.h
+++ b/arch/x86/oprofile/op_counter.h
@@ -10,7 +10,7 @@
 #ifndef OP_COUNTER_H
 #define OP_COUNTER_H
 
-#define OP_MAX_COUNTER 8
+#define OP_MAX_COUNTER 32
 
 /* Per-perfctr configuration as set via
  * oprofilefs.
diff --git a/arch/x86/oprofile/op_model_amd.c b/arch/x86/oprofile/op_model_amd.c
index f676f88..fdbed3a 100644
--- a/arch/x86/oprofile/op_model_amd.c
+++ b/arch/x86/oprofile/op_model_amd.c
@@ -9,12 +9,15 @@
  * @author Philippe Elie
  * @author Graydon Hoare
  * @author Robert Richter <robert.richter@amd.com>
- * @author Barry Kasindorf
+ * @author Barry Kasindorf <barry.kasindorf@amd.com>
+ * @author Jason Yeh <jason.yeh@amd.com>
+ * @author Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
  */
 
 #include <linux/oprofile.h>
 #include <linux/device.h>
 #include <linux/pci.h>
+#include <linux/percpu.h>
 
 #include <asm/ptrace.h>
 #include <asm/msr.h>
@@ -25,12 +28,23 @@
 
 #define NUM_COUNTERS 4
 #define NUM_CONTROLS 4
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+#define NUM_VIRT_COUNTERS 32
+#define NUM_VIRT_CONTROLS 32
+#else
+#define NUM_VIRT_COUNTERS NUM_COUNTERS
+#define NUM_VIRT_CONTROLS NUM_CONTROLS
+#endif
+
 #define OP_EVENT_MASK			0x0FFF
 #define OP_CTR_OVERFLOW			(1ULL<<31)
 
 #define MSR_AMD_EVENTSEL_RESERVED	((0xFFFFFCF0ULL<<32)|(1ULL<<21))
 
-static unsigned long reset_value[NUM_COUNTERS];
+static unsigned long reset_value[NUM_VIRT_COUNTERS];
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+DECLARE_PER_CPU(int, switch_index);
+#endif
 
 #ifdef CONFIG_OPROFILE_IBS
 
@@ -82,6 +96,16 @@
 		else
 			msrs->controls[i].addr = 0;
 	}
+
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	for (i = 0; i < NUM_VIRT_COUNTERS; i++) {
+		int hw_counter = i % NUM_CONTROLS;
+		if (reserve_perfctr_nmi(MSR_K7_PERFCTR0 + i))
+			msrs->multiplex[i].addr = MSR_K7_PERFCTR0 + hw_counter;
+		else
+			msrs->multiplex[i].addr = 0;
+	}
+#endif
 }
 
 static void op_amd_setup_ctrs(struct op_x86_model_spec const *model,
@@ -90,6 +114,15 @@
 	u64 val;
 	int i;
 
+	/* setup reset_value */
+	for (i = 0; i < NUM_VIRT_COUNTERS; ++i) {
+		if (counter_config[i].enabled) {
+			reset_value[i] = counter_config[i].count;
+		} else {
+			reset_value[i] = 0;
+		}
+	}
+
 	/* clear all counters */
 	for (i = 0; i < NUM_CONTROLS; ++i) {
 		if (unlikely(!msrs->controls[i].addr))
@@ -108,20 +141,49 @@
 
 	/* enable active counters */
 	for (i = 0; i < NUM_COUNTERS; ++i) {
-		if (counter_config[i].enabled && msrs->counters[i].addr) {
-			reset_value[i] = counter_config[i].count;
-			wrmsrl(msrs->counters[i].addr,
-			       -(u64)counter_config[i].count);
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+		int offset = i + __get_cpu_var(switch_index);
+#else
+		int offset = i;
+#endif
+		if (counter_config[offset].enabled && msrs->counters[i].addr) {
+			/* setup counter registers */
+			wrmsrl(msrs->counters[i].addr, -(u64)reset_value[offset]);
+
+			/* setup control registers */
 			rdmsrl(msrs->controls[i].addr, val);
 			val &= model->reserved;
-			val |= op_x86_get_ctrl(model, &counter_config[i]);
+			val |= op_x86_get_ctrl(model, &counter_config[offset]);
 			wrmsrl(msrs->controls[i].addr, val);
-		} else {
-			reset_value[i] = 0;
 		}
 	}
 }
 
+
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+
+static void op_amd_switch_ctrl(struct op_x86_model_spec const *model,
+			       struct op_msrs const * const msrs)
+{
+	u64 val;
+	int i;
+
+	/* enable active counters */
+	for (i = 0; i < NUM_COUNTERS; ++i) {
+		int offset = i + __get_cpu_var(switch_index);
+		if (counter_config[offset].enabled) {
+			/* setup control registers */
+			rdmsrl(msrs->controls[i].addr, val);
+			val &= model->reserved;
+			val |= op_x86_get_ctrl(model, &counter_config[offset]);
+			wrmsrl(msrs->controls[i].addr, val);
+		}
+	}
+}
+
+#endif
+
+
 #ifdef CONFIG_OPROFILE_IBS
 
 static inline int
@@ -230,14 +292,19 @@
 	int i;
 
 	for (i = 0; i < NUM_COUNTERS; ++i) {
-		if (!reset_value[i])
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+		int offset = i + __get_cpu_var(switch_index);
+#else
+		int offset = i;
+#endif
+		if (!reset_value[offset])
 			continue;
 		rdmsrl(msrs->counters[i].addr, val);
 		/* bit is clear if overflowed: */
 		if (val & OP_CTR_OVERFLOW)
 			continue;
-		oprofile_add_sample(regs, i);
-		wrmsrl(msrs->counters[i].addr, -(u64)reset_value[i]);
+		oprofile_add_sample(regs, offset);
+		wrmsrl(msrs->counters[i].addr, -(u64)reset_value[offset]);
 	}
 
 	op_amd_handle_ibs(regs, msrs);
@@ -250,8 +317,14 @@
 {
 	u64 val;
 	int i;
+
 	for (i = 0; i < NUM_COUNTERS; ++i) {
-		if (reset_value[i]) {
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+		int offset = i + __get_cpu_var(switch_index);
+#else
+		int offset = i;
+#endif
+		if (reset_value[offset]) {
 			rdmsrl(msrs->controls[i].addr, val);
 			val |= ARCH_PERFMON_EVENTSEL0_ENABLE;
 			wrmsrl(msrs->controls[i].addr, val);
@@ -271,7 +344,11 @@
 	 * pm callback
 	 */
 	for (i = 0; i < NUM_COUNTERS; ++i) {
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+		if (!reset_value[i + per_cpu(switch_index, smp_processor_id())])
+#else
 		if (!reset_value[i])
+#endif
 			continue;
 		rdmsrl(msrs->controls[i].addr, val);
 		val &= ~ARCH_PERFMON_EVENTSEL0_ENABLE;
@@ -289,7 +366,7 @@
 		if (msrs->counters[i].addr)
 			release_perfctr_nmi(MSR_K7_PERFCTR0 + i);
 	}
-	for (i = 0; i < NUM_CONTROLS; ++i) {
+	for (i = 0; i < NUM_COUNTERS; ++i) {
 		if (msrs->controls[i].addr)
 			release_evntsel_nmi(MSR_K7_EVNTSEL0 + i);
 	}
@@ -463,6 +540,8 @@
 struct op_x86_model_spec const op_amd_spec = {
 	.num_counters		= NUM_COUNTERS,
 	.num_controls		= NUM_CONTROLS,
+	.num_virt_counters	= NUM_VIRT_COUNTERS,
+	.num_virt_controls	= NUM_VIRT_CONTROLS,
 	.reserved		= MSR_AMD_EVENTSEL_RESERVED,
 	.event_mask		= OP_EVENT_MASK,
 	.init			= op_amd_init,
@@ -473,4 +552,7 @@
 	.start			= &op_amd_start,
 	.stop			= &op_amd_stop,
 	.shutdown		= &op_amd_shutdown,
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	.switch_ctrl		= &op_amd_switch_ctrl,
+#endif
 };
diff --git a/arch/x86/oprofile/op_model_p4.c b/arch/x86/oprofile/op_model_p4.c
index 5921b7f..65b9237 100644
--- a/arch/x86/oprofile/op_model_p4.c
+++ b/arch/x86/oprofile/op_model_p4.c
@@ -698,6 +698,8 @@
 struct op_x86_model_spec const op_p4_ht2_spec = {
 	.num_counters		= NUM_COUNTERS_HT2,
 	.num_controls		= NUM_CONTROLS_HT2,
+	.num_virt_counters	= NUM_COUNTERS_HT2,
+	.num_virt_controls	= NUM_CONTROLS_HT2,
 	.fill_in_addresses	= &p4_fill_in_addresses,
 	.setup_ctrs		= &p4_setup_ctrs,
 	.check_ctrs		= &p4_check_ctrs,
@@ -710,6 +712,8 @@
 struct op_x86_model_spec const op_p4_spec = {
 	.num_counters		= NUM_COUNTERS_NON_HT,
 	.num_controls		= NUM_CONTROLS_NON_HT,
+	.num_virt_counters	= NUM_COUNTERS_NON_HT,
+	.num_virt_controls	= NUM_CONTROLS_NON_HT,
 	.fill_in_addresses	= &p4_fill_in_addresses,
 	.setup_ctrs		= &p4_setup_ctrs,
 	.check_ctrs		= &p4_check_ctrs,
diff --git a/arch/x86/oprofile/op_model_ppro.c b/arch/x86/oprofile/op_model_ppro.c
index 570d717..098cbca 100644
--- a/arch/x86/oprofile/op_model_ppro.c
+++ b/arch/x86/oprofile/op_model_ppro.c
@@ -206,6 +206,8 @@
 struct op_x86_model_spec const op_ppro_spec = {
 	.num_counters		= 2,
 	.num_controls		= 2,
+	.num_virt_counters	= 2,
+	.num_virt_controls	= 2,
 	.reserved		= MSR_PPRO_EVENTSEL_RESERVED,
 	.fill_in_addresses	= &ppro_fill_in_addresses,
 	.setup_ctrs		= &ppro_setup_ctrs,
diff --git a/arch/x86/oprofile/op_x86_model.h b/arch/x86/oprofile/op_x86_model.h
index 5054898..0d07d23 100644
--- a/arch/x86/oprofile/op_x86_model.h
+++ b/arch/x86/oprofile/op_x86_model.h
@@ -23,6 +23,7 @@
 struct op_msrs {
 	struct op_msr *counters;
 	struct op_msr *controls;
+	struct op_msr *multiplex;
 };
 
 struct pt_regs;
@@ -35,6 +36,8 @@
 struct op_x86_model_spec {
 	unsigned int	num_counters;
 	unsigned int	num_controls;
+	unsigned int	num_virt_counters;
+	unsigned int	num_virt_controls;
 	u64		reserved;
 	u16		event_mask;
 	int		(*init)(struct oprofile_operations *ops);
@@ -47,6 +50,10 @@
 	void		(*start)(struct op_msrs const * const msrs);
 	void		(*stop)(struct op_msrs const * const msrs);
 	void		(*shutdown)(struct op_msrs const * const msrs);
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	void		(*switch_ctrl)(struct op_x86_model_spec const *model,
+				       struct op_msrs const * const msrs);
+#endif
 };
 
 struct op_counter_config;
diff --git a/drivers/oprofile/oprof.c b/drivers/oprofile/oprof.c
index 3cffce9..7bc64af 100644
--- a/drivers/oprofile/oprof.c
+++ b/drivers/oprofile/oprof.c
@@ -12,6 +12,8 @@
 #include <linux/init.h>
 #include <linux/oprofile.h>
 #include <linux/moduleparam.h>
+#include <linux/workqueue.h>
+#include <linux/time.h>
 #include <asm/mutex.h>
 
 #include "oprof.h"
@@ -27,6 +29,15 @@
 static unsigned long is_setup;
 static DEFINE_MUTEX(start_mutex);
 
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+
+static void switch_worker(struct work_struct *work);
+static DECLARE_DELAYED_WORK(switch_work, switch_worker);
+unsigned long timeout_jiffies;
+#define MULTIPLEXING_TIMER_DEFAULT 1
+
+#endif
+
 /* timer
    0 - use performance monitoring hardware if available
    1 - use the timer int mechanism regardless
@@ -87,6 +98,20 @@
 	return err;
 }
 
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+
+static void start_switch_worker(void)
+{
+	schedule_delayed_work(&switch_work, timeout_jiffies);
+}
+
+static void switch_worker(struct work_struct *work)
+{
+	if (!oprofile_ops.switch_events())
+		start_switch_worker();
+}
+
+#endif
 
 /* Actually start profiling (echo 1>/dev/oprofile/enable) */
 int oprofile_start(void)
@@ -108,6 +133,11 @@
 	if ((err = oprofile_ops.start()))
 		goto out;
 
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	if (oprofile_ops.switch_events)
+		start_switch_worker();
+#endif
+
 	oprofile_started = 1;
 out:
 	mutex_unlock(&start_mutex);
@@ -123,6 +153,11 @@
 		goto out;
 	oprofile_ops.stop();
 	oprofile_started = 0;
+
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	cancel_delayed_work_sync(&switch_work);
+#endif
+
 	/* wake up the daemon to read what remains */
 	wake_up_buffer_waiter();
 out:
@@ -155,6 +190,36 @@
 	mutex_unlock(&start_mutex);
 }
 
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+
+/* User inputs in ms, converts to jiffies */
+int oprofile_set_timeout(unsigned long val_msec)
+{
+	int err = 0;
+
+	mutex_lock(&start_mutex);
+
+	if (oprofile_started) {
+		err = -EBUSY;
+		goto out;
+	}
+
+	if (!oprofile_ops.switch_events) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	timeout_jiffies = msecs_to_jiffies(val_msec);
+	if (timeout_jiffies == MAX_JIFFY_OFFSET)
+		timeout_jiffies = msecs_to_jiffies(MULTIPLEXING_TIMER_DEFAULT);
+
+out:
+	mutex_unlock(&start_mutex);
+	return err;
+
+}
+
+#endif
 
 int oprofile_set_backtrace(unsigned long val)
 {
@@ -179,10 +244,23 @@
 	return err;
 }
 
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+
+static void __init oprofile_multiplexing_init(void)
+{
+	timeout_jiffies = msecs_to_jiffies(MULTIPLEXING_TIMER_DEFAULT);
+}
+
+#endif
+
 static int __init oprofile_init(void)
 {
 	int err;
 
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	oprofile_multiplexing_init();
+#endif
+
 	err = oprofile_arch_init(&oprofile_ops);
 
 	if (err < 0 || timer) {
diff --git a/drivers/oprofile/oprof.h b/drivers/oprofile/oprof.h
index c288d3c..ee38abc 100644
--- a/drivers/oprofile/oprof.h
+++ b/drivers/oprofile/oprof.h
@@ -27,6 +27,7 @@
 extern struct oprofile_operations oprofile_ops;
 extern unsigned long oprofile_started;
 extern unsigned long oprofile_backtrace_depth;
+extern unsigned long timeout_jiffies;
 
 struct super_block;
 struct dentry;
@@ -35,5 +36,6 @@
 void oprofile_timer_init(struct oprofile_operations *ops);
 
 int oprofile_set_backtrace(unsigned long depth);
+int oprofile_set_timeout(unsigned long time);
 
 #endif /* OPROF_H */
diff --git a/drivers/oprofile/oprofile_files.c b/drivers/oprofile/oprofile_files.c
index 5d36ffc..468ec3e 100644
--- a/drivers/oprofile/oprofile_files.c
+++ b/drivers/oprofile/oprofile_files.c
@@ -9,6 +9,7 @@
 
 #include <linux/fs.h>
 #include <linux/oprofile.h>
+#include <linux/jiffies.h>
 
 #include "event_buffer.h"
 #include "oprofile_stats.h"
@@ -22,6 +23,45 @@
 unsigned long oprofile_cpu_buffer_size;
 unsigned long oprofile_buffer_watershed;
 
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+
+static ssize_t timeout_read(struct file *file, char __user *buf,
+		size_t count, loff_t *offset)
+{
+	return oprofilefs_ulong_to_user(jiffies_to_msecs(timeout_jiffies),
+				buf, count, offset);
+}
+
+
+static ssize_t timeout_write(struct file *file, char const __user *buf,
+		size_t count, loff_t *offset)
+{
+	unsigned long val;
+	int retval;
+
+	if (*offset)
+		return -EINVAL;
+
+	retval = oprofilefs_ulong_from_user(&val, buf, count);
+	if (retval)
+		return retval;
+
+	retval = oprofile_set_timeout(val);
+
+	if (retval)
+		return retval;
+	return count;
+}
+
+
+static const struct file_operations timeout_fops = {
+	.read		= timeout_read,
+	.write		= timeout_write,
+};
+
+#endif
+
+
 static ssize_t depth_read(struct file *file, char __user *buf, size_t count, loff_t *offset)
 {
 	return oprofilefs_ulong_to_user(oprofile_backtrace_depth, buf, count,
@@ -139,6 +179,9 @@
 	oprofilefs_create_file(sb, root, "cpu_type", &cpu_type_fops);
 	oprofilefs_create_file(sb, root, "backtrace_depth", &depth_fops);
 	oprofilefs_create_file(sb, root, "pointer_size", &pointer_size_fops);
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	oprofilefs_create_file(sb, root, "time_slice", &timeout_fops);
+#endif
 	oprofile_create_stats_files(sb, root);
 	if (oprofile_ops.create_files)
 		oprofile_ops.create_files(sb, root);
diff --git a/drivers/oprofile/oprofile_stats.c b/drivers/oprofile/oprofile_stats.c
index 3c2270a..77a57a6 100644
--- a/drivers/oprofile/oprofile_stats.c
+++ b/drivers/oprofile/oprofile_stats.c
@@ -16,6 +16,9 @@
 #include "cpu_buffer.h"
 
 struct oprofile_stat_struct oprofile_stats;
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+atomic_t multiplex_counter;
+#endif
 
 void oprofile_reset_stats(void)
 {
@@ -34,6 +37,9 @@
 	atomic_set(&oprofile_stats.sample_lost_no_mapping, 0);
 	atomic_set(&oprofile_stats.event_lost_overflow, 0);
 	atomic_set(&oprofile_stats.bt_lost_no_mapping, 0);
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	atomic_set(&multiplex_counter, 0);
+#endif
 }
 
 
@@ -76,4 +82,8 @@
 		&oprofile_stats.event_lost_overflow);
 	oprofilefs_create_ro_atomic(sb, dir, "bt_lost_no_mapping",
 		&oprofile_stats.bt_lost_no_mapping);
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	oprofilefs_create_ro_atomic(sb, dir, "multiplex_counter",
+		&multiplex_counter);
+#endif
 }
diff --git a/include/linux/oprofile.h b/include/linux/oprofile.h
index d68d2ed..5171639 100644
--- a/include/linux/oprofile.h
+++ b/include/linux/oprofile.h
@@ -67,6 +67,9 @@
 
 	/* Initiate a stack backtrace. Optional. */
 	void (*backtrace)(struct pt_regs * const regs, unsigned int depth);
+
+	/* Multiplex between different events. Optional. */
+	int (*switch_events)(void);
 	/* CPU identification string. */
 	char * cpu_type;
 };