12 files changed, 415 insertions, 20 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index 99193b160232..beea3ccebb5e 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -30,6 +30,18 @@ config OPROFILE_IBS
 
           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 fca8dc94531e..e54f6a0b35ac 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 @@ static DEFINE_PER_CPU(unsigned long, saved_lvtpc);
 /* 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 @@ static void free_msrs(void)
                 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 @@ static int allocate_msrs(void)
         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 @@ static int allocate_msrs(void)
                         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 @@ static int allocate_msrs(void)
         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 @@ static void nmi_cpu_setup(void *dummy)
         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 @@ static int nmi_setup(void)
                         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 @@ static void nmi_cpu_shutdown(void *dummy)
         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 @@ static void nmi_stop(void)
         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 @@ static int nmi_create_files(struct super_block *sb, struct dentry *root)
                  */
                 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 @@ static int nmi_create_files(struct super_block *sb, struct dentry *root)
         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 @@ int __init op_nmi_init(struct oprofile_operations *ops)
         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 91b6a116165e..e28398df0df2 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 f676f8825a3f..fdbed3a0c877 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 @@ static void op_amd_fill_in_addresses(struct op_msrs * const msrs)
                 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 @@ static void op_amd_setup_ctrs(struct op_x86_model_spec const *model,
         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 @@ static void op_amd_setup_ctrs(struct op_x86_model_spec const *model,
 
         /* 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);
+                }
+        }
+}
+
+
+#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);
-                } else {
-                        reset_value[i] = 0;
                 }
         }
 }
 
+#endif
+
+
 #ifdef CONFIG_OPROFILE_IBS
 
 static inline int
@@ -230,14 +292,19 @@ static int op_amd_check_ctrs(struct pt_regs * const regs,
         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 @@ static void op_amd_start(struct op_msrs const * const msrs)
 {
         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 @@ static void op_amd_stop(struct op_msrs const * const msrs)
          * 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 @@ static void op_amd_shutdown(struct op_msrs const * const msrs)
                 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 @@ static void op_amd_exit(void) {}
 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 @@ struct op_x86_model_spec const op_amd_spec = {
         .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 5921b7fc724b..65b9237cde8b 100644
--- a/arch/x86/oprofile/op_model_p4.c
+++ b/arch/x86/oprofile/op_model_p4.c
@@ -698,6 +698,8 @@ static void p4_shutdown(struct op_msrs const * const msrs)
 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_ht2_spec = {
 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 570d717c3308..098cbca5c0b0 100644
--- a/arch/x86/oprofile/op_model_ppro.c
+++ b/arch/x86/oprofile/op_model_ppro.c
@@ -206,6 +206,8 @@ static void ppro_shutdown(struct op_msrs const * const msrs)
 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 505489873b9d..0d07d23cb062 100644
--- a/arch/x86/oprofile/op_x86_model.h
+++ b/arch/x86/oprofile/op_x86_model.h
@@ -23,6 +23,7 @@ struct op_msr {
 struct op_msrs {
         struct op_msr *counters;
         struct op_msr *controls;
+        struct op_msr *multiplex;
 };
 
 struct pt_regs;
@@ -35,6 +36,8 @@ struct oprofile_operations;
 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 @@ struct op_x86_model_spec {
         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 3cffce90f82a..7bc64af7cf99 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 @@ unsigned long oprofile_backtrace_depth;
 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 @@ out:
         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 @@ int oprofile_start(void)
         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 @@ void oprofile_stop(void)
                 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 @@ post_sync:
         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 @@ out:
         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 c288d3c24b50..ee38abcc74f3 100644
--- a/drivers/oprofile/oprof.h
+++ b/drivers/oprofile/oprof.h
@@ -27,6 +27,7 @@ extern unsigned long oprofile_buffer_watershed;
 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_create_files(struct super_block *sb, struct dentry *root);
 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 5d36ffc30dd5..468ec3e4f856 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_buffer_size;
 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 @@ void oprofile_create_files(struct super_block *sb, struct dentry *root)
         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 3c2270a8300c..77a57a6792f6 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 @@ void oprofile_reset_stats(void)
         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 @@ void oprofile_create_stats_files(struct super_block *sb, struct dentry *root)
                 &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 d68d2ed94f15..5171639ecf0f 100644
--- a/include/linux/oprofile.h
+++ b/include/linux/oprofile.h
@@ -67,6 +67,9 @@ struct oprofile_operations {
 
         /* 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;
 };