Oprofile Multiplexing Patch

This patch introduces multiplexing support for the Oprofile kernel
module. It basically adds a new function pointer in oprofile_operator
allowing each architecture to supply its callback to switch between
different sets of event when the timer expires. Userspace tools can
modify the time slice through /dev/oprofile/time_slice.

It also modifies the number of counters exposed to the userspace through
/dev/oprofile. For example, the number of counters for AMD CPUs are
changed to 32 and multiplexed in the sets of 4.

Signed-off-by: Jason Yeh <jason.yeh@amd.com>
Signed-off-by: Robert Richter <robert.richter@amd.com>
Cc: oprofile-list <oprofile-list@lists.sourceforge.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

10 files changed, 247 insertions, 45 deletions

diff --git a/arch/x86/oprofile/nmi_int.c b/arch/x86/oprofile/nmi_int.c
index 287513a09819..2a65fe7680ab 100644
--- a/arch/x86/oprofile/nmi_int.c
+++ b/arch/x86/oprofile/nmi_int.c
@@ -23,12 +23,18 @@
 #include "op_counter.h"
 #include "op_x86_model.h"
 
+DEFINE_PER_CPU(int, switch_index);
+
 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);
 
 static int nmi_start(void);
 static void nmi_stop(void);
+static void nmi_cpu_save_mpx_registers(struct op_msrs *msrs);
+static void nmi_cpu_restore_mpx_registers(struct op_msrs *msrs);
+static void nmi_cpu_stop(void *dummy);
+static void nmi_cpu_start(void *dummy);
 
 /* 0 == registered but off, 1 == registered and on */
 static int nmi_enabled = 0;
@@ -81,6 +87,47 @@ static void exit_sysfs(void)
 #define exit_sysfs() do { } while (0)
 #endif /* CONFIG_PM */
 
+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_hardware_counters;
+        if ((si > model->num_counters) || (counter_config[si].count == 0))
+                per_cpu(switch_index, smp_processor_id()) = 0;
+        else
+                per_cpu(switch_index, smp_processor_id()) = si;
+
+        nmi_cpu_restore_mpx_registers(msrs);
+        model->setup_ctrs(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_hardware_counters].count ? 0 : -EINVAL;
+}
+
+static int nmi_switch_event(void)
+{
+        if (nmi_multiplex_on() < 0)
+                return -EINVAL;
+
+        on_each_cpu(nmi_cpu_switch, NULL, 0, 1);
+
+        return 0;
+}
+
 static int profile_exceptions_notify(struct notifier_block *self,
                                      unsigned long val, void *data)
 {
@@ -144,11 +191,10 @@ static void free_msrs(void)
 
 static int allocate_msrs(void)
 {
-        int success = 1;
+        int i, success = 1;
         size_t controls_size = sizeof(struct op_msr) * model->num_controls;
         size_t counters_size = sizeof(struct op_msr) * model->num_counters;
 
-        int i;
         for_each_possible_cpu(i) {
                 per_cpu(cpu_msrs, i).counters = kmalloc(counters_size,
                                                                 GFP_KERNEL);
@@ -156,8 +202,8 @@ static int allocate_msrs(void)
                         success = 0;
                         break;
                 }
-                per_cpu(cpu_msrs, i).controls = kmalloc(controls_size,
-                                                                GFP_KERNEL);
+                per_cpu(cpu_msrs, i).controls =
+                                kmalloc(controls_size, GFP_KERNEL);
                 if (!per_cpu(cpu_msrs, i).controls) {
                         success = 0;
                         break;
@@ -201,7 +247,8 @@ static int nmi_setup(void)
                 return err;
         }
 
-        /* We need to serialize save and setup for HT because the subset
+        /*
+         * We need to serialize save and setup for HT because the subset
          * of msrs are distinct for save and setup operations
          */
 
@@ -217,7 +264,6 @@ static int nmi_setup(void)
                                 per_cpu(cpu_msrs, 0).controls,
                                 sizeof(struct op_msr) * model->num_controls);
                 }
-
         }
         on_each_cpu(nmi_save_registers, NULL, 1);
         on_each_cpu(nmi_cpu_setup, NULL, 1);
@@ -225,7 +271,41 @@ static int nmi_setup(void)
         return 0;
 }
 
-static void nmi_restore_registers(struct op_msrs *msrs)
+static void nmi_cpu_save_mpx_registers(struct op_msrs *msrs)
+{
+        unsigned int si = __get_cpu_var(switch_index);
+        unsigned int const nr_ctrs = model->num_hardware_counters;
+        struct op_msr *counters = &msrs->counters[si];
+        unsigned int i;
+
+        for (i = 0; i < nr_ctrs; ++i) {
+                int offset = i + si;
+                if (counters[offset].addr) {
+                        rdmsr(counters[offset].addr,
+                                counters[offset].multiplex.low,
+                                counters[offset].multiplex.high);
+                }
+        }
+}
+
+static void nmi_cpu_restore_mpx_registers(struct op_msrs *msrs)
+{
+        unsigned int si = __get_cpu_var(switch_index);
+        unsigned int const nr_ctrs = model->num_hardware_counters;
+        struct op_msr *counters = &msrs->counters[si];
+        unsigned int i;
+
+        for (i = 0; i < nr_ctrs; ++i) {
+                int offset = i + si;
+                if (counters[offset].addr) {
+                        wrmsr(counters[offset].addr,
+                                counters[offset].multiplex.low,
+                                counters[offset].multiplex.high);
+                }
+        }
+}
+
+static void nmi_cpu_restore_registers(struct op_msrs *msrs)
 {
         unsigned int const nr_ctrs = model->num_counters;
         unsigned int const nr_ctrls = model->num_controls;
@@ -265,7 +345,8 @@ static void nmi_cpu_shutdown(void *dummy)
         apic_write(APIC_LVTERR, v | APIC_LVT_MASKED);
         apic_write(APIC_LVTPC, per_cpu(saved_lvtpc, cpu));
         apic_write(APIC_LVTERR, v);
-        nmi_restore_registers(msrs);
+        nmi_cpu_restore_registers(msrs);
+        __get_cpu_var(switch_index) = 0;
 }
 
 static void nmi_shutdown(void)
@@ -328,6 +409,7 @@ static int nmi_create_files(struct super_block *sb, struct dentry *root)
                 oprofilefs_create_ulong(sb, dir, "unit_mask", &counter_config[i].unit_mask);
                 oprofilefs_create_ulong(sb, dir, "kernel", &counter_config[i].kernel);
                 oprofilefs_create_ulong(sb, dir, "user", &counter_config[i].user);
+                counter_config[i].save_count_low = 0;
         }
 
         return 0;
@@ -469,12 +551,14 @@ int __init op_nmi_init(struct oprofile_operations *ops)
         }
 
         /* default values, can be overwritten by model */
+        __get_cpu_var(switch_index) = 0;
         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;
+        ops->switch_events = nmi_switch_event;
 
         if (model->init)
                 ret = model->init(ops);
diff --git a/arch/x86/oprofile/op_counter.h b/arch/x86/oprofile/op_counter.h
index 2880b15c4675..786d6e01cf7f 100644
--- a/arch/x86/oprofile/op_counter.h
+++ b/arch/x86/oprofile/op_counter.h
@@ -10,13 +10,14 @@
 #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.
  */
 struct op_counter_config {
         unsigned long count;
+                unsigned long save_count_low;
         unsigned long enabled;
         unsigned long event;
         unsigned long kernel;
diff --git a/arch/x86/oprofile/op_model_amd.c b/arch/x86/oprofile/op_model_amd.c
index d9faf607b3a6..bbf2b68bcc5d 100644
--- a/arch/x86/oprofile/op_model_amd.c
+++ b/arch/x86/oprofile/op_model_amd.c
@@ -15,6 +15,7 @@
 #include <linux/oprofile.h>
 #include <linux/device.h>
 #include <linux/pci.h>
+#include <linux/percpu.h>
 
 #include <asm/ptrace.h>
 #include <asm/msr.h>
@@ -23,8 +24,10 @@
 #include "op_x86_model.h"
 #include "op_counter.h"
 
-#define NUM_COUNTERS 4
-#define NUM_CONTROLS 4
+#define NUM_COUNTERS 32
+#define NUM_HARDWARE_COUNTERS 4
+#define NUM_CONTROLS 32
+#define NUM_HARDWARE_CONTROLS 4
 
 #define CTR_IS_RESERVED(msrs, c) (msrs->counters[(c)].addr ? 1 : 0)
 #define CTR_READ(l, h, msrs, c) do {rdmsr(msrs->counters[(c)].addr, (l), (h)); } while (0)
@@ -48,6 +51,7 @@
 #define CTRL_SET_GUEST_ONLY(val, h) (val |= ((h & 1) << 8))
 
 static unsigned long reset_value[NUM_COUNTERS];
+DECLARE_PER_CPU(int, switch_index);
 
 #ifdef CONFIG_OPROFILE_IBS
 
@@ -130,15 +134,17 @@ static void op_amd_fill_in_addresses(struct op_msrs * const msrs)
         int i;
 
         for (i = 0; i < NUM_COUNTERS; i++) {
-                if (reserve_perfctr_nmi(MSR_K7_PERFCTR0 + i))
-                        msrs->counters[i].addr = MSR_K7_PERFCTR0 + i;
+                int hw_counter = i % NUM_HARDWARE_COUNTERS;
+                if (reserve_perfctr_nmi(MSR_K7_PERFCTR0 + hw_counter))
+                        msrs->counters[i].addr = MSR_K7_PERFCTR0 + hw_counter;
                 else
                         msrs->counters[i].addr = 0;
         }
 
         for (i = 0; i < NUM_CONTROLS; i++) {
-                if (reserve_evntsel_nmi(MSR_K7_EVNTSEL0 + i))
-                        msrs->controls[i].addr = MSR_K7_EVNTSEL0 + i;
+                int hw_control = i % NUM_HARDWARE_CONTROLS;
+                if (reserve_evntsel_nmi(MSR_K7_EVNTSEL0 + hw_control))
+                        msrs->controls[i].addr = MSR_K7_EVNTSEL0 + hw_control;
                 else
                         msrs->controls[i].addr = 0;
         }
@@ -150,8 +156,16 @@ static void op_amd_setup_ctrs(struct op_msrs const * const msrs)
         unsigned int low, high;
         int i;
 
+        for (i = 0; i < NUM_HARDWARE_CONTROLS; ++i) {
+                int offset = i + __get_cpu_var(switch_index);
+                if (counter_config[offset].enabled)
+                        reset_value[offset] = counter_config[offset].count;
+                else
+                        reset_value[offset] = 0;
+        }
+
         /* clear all counters */
-        for (i = 0 ; i < NUM_CONTROLS; ++i) {
+        for (i = 0 ; i < NUM_HARDWARE_CONTROLS; ++i) {
                 if (unlikely(!CTRL_IS_RESERVED(msrs, i)))
                         continue;
                 CTRL_READ(low, high, msrs, i);
@@ -161,34 +175,31 @@ static void op_amd_setup_ctrs(struct op_msrs const * const msrs)
         }
 
         /* avoid a false detection of ctr overflows in NMI handler */
-        for (i = 0; i < NUM_COUNTERS; ++i) {
+        for (i = 0; i < NUM_HARDWARE_COUNTERS; ++i) {
                 if (unlikely(!CTR_IS_RESERVED(msrs, i)))
                         continue;
                 CTR_WRITE(1, msrs, i);
         }
 
         /* enable active counters */
-        for (i = 0; i < NUM_COUNTERS; ++i) {
-                if ((counter_config[i].enabled) && (CTR_IS_RESERVED(msrs, i))) {
-                        reset_value[i] = counter_config[i].count;
-
-                        CTR_WRITE(counter_config[i].count, msrs, i);
+        for (i = 0; i < NUM_HARDWARE_COUNTERS; ++i) {
+                int offset = i + __get_cpu_var(switch_index);
+                if ((counter_config[offset].enabled) && (CTR_IS_RESERVED(msrs, i))) {
+                        CTR_WRITE(counter_config[offset].count, msrs, i);
 
                         CTRL_READ(low, high, msrs, i);
                         CTRL_CLEAR_LO(low);
                         CTRL_CLEAR_HI(high);
                         CTRL_SET_ENABLE(low);
-                        CTRL_SET_USR(low, counter_config[i].user);
-                        CTRL_SET_KERN(low, counter_config[i].kernel);
-                        CTRL_SET_UM(low, counter_config[i].unit_mask);
-                        CTRL_SET_EVENT_LOW(low, counter_config[i].event);
-                        CTRL_SET_EVENT_HIGH(high, counter_config[i].event);
+                        CTRL_SET_USR(low, counter_config[offset].user);
+                        CTRL_SET_KERN(low, counter_config[offset].kernel);
+                        CTRL_SET_UM(low, counter_config[offset].unit_mask);
+                        CTRL_SET_EVENT_LOW(low, counter_config[offset].event);
+                        CTRL_SET_EVENT_HIGH(high, counter_config[offset].event);
                         CTRL_SET_HOST_ONLY(high, 0);
                         CTRL_SET_GUEST_ONLY(high, 0);
 
                         CTRL_WRITE(low, high, msrs, i);
-                } else {
-                        reset_value[i] = 0;
                 }
         }
 }
@@ -276,13 +287,14 @@ static int op_amd_check_ctrs(struct pt_regs * const regs,
         unsigned int low, high;
         int i;
 
-        for (i = 0 ; i < NUM_COUNTERS; ++i) {
-                if (!reset_value[i])
+        for (i = 0 ; i < NUM_HARDWARE_COUNTERS ; ++i) {
+                int offset = i + __get_cpu_var(switch_index);
+                if (!reset_value[offset])
                         continue;
                 CTR_READ(low, high, msrs, i);
                 if (CTR_OVERFLOWED(low)) {
-                        oprofile_add_sample(regs, i);
-                        CTR_WRITE(reset_value[i], msrs, i);
+                        oprofile_add_sample(regs, offset);
+                        CTR_WRITE(reset_value[offset], msrs, i);
                 }
         }
 
@@ -298,8 +310,10 @@ static void op_amd_start(struct op_msrs const * const msrs)
 {
         unsigned int low, high;
         int i;
-        for (i = 0 ; i < NUM_COUNTERS ; ++i) {
-                if (reset_value[i]) {
+
+        for (i = 0 ; i < NUM_HARDWARE_COUNTERS ; ++i) {
+                int offset = i + __get_cpu_var(switch_index);
+                if (reset_value[offset]) {
                         CTRL_READ(low, high, msrs, i);
                         CTRL_SET_ACTIVE(low);
                         CTRL_WRITE(low, high, msrs, i);
@@ -329,8 +343,8 @@ static void op_amd_stop(struct op_msrs const * const msrs)
 
         /* Subtle: stop on all counters to avoid race with
          * setting our pm callback */
-        for (i = 0 ; i < NUM_COUNTERS ; ++i) {
-                if (!reset_value[i])
+        for (i = 0 ; i < NUM_HARDWARE_COUNTERS ; ++i) {
+                if (!reset_value[i + per_cpu(switch_index, smp_processor_id())])
                         continue;
                 CTRL_READ(low, high, msrs, i);
                 CTRL_SET_INACTIVE(low);
@@ -356,11 +370,11 @@ static void op_amd_shutdown(struct op_msrs const * const msrs)
 {
         int i;
 
-        for (i = 0 ; i < NUM_COUNTERS ; ++i) {
+        for (i = 0 ; i < NUM_HARDWARE_COUNTERS ; ++i) {
                 if (CTR_IS_RESERVED(msrs, i))
                         release_perfctr_nmi(MSR_K7_PERFCTR0 + i);
         }
-        for (i = 0 ; i < NUM_CONTROLS ; ++i) {
+        for (i = 0 ; i < NUM_HARDWARE_COUNTERS ; ++i) {
                 if (CTRL_IS_RESERVED(msrs, i))
                         release_evntsel_nmi(MSR_K7_EVNTSEL0 + i);
         }
@@ -534,6 +548,8 @@ struct op_x86_model_spec const op_amd_spec = {
         .exit = op_amd_exit,
         .num_counters = NUM_COUNTERS,
         .num_controls = NUM_CONTROLS,
+        .num_hardware_counters = NUM_HARDWARE_COUNTERS,
+        .num_hardware_controls = NUM_HARDWARE_CONTROLS,
         .fill_in_addresses = &op_amd_fill_in_addresses,
         .setup_ctrs = &op_amd_setup_ctrs,
         .check_ctrs = &op_amd_check_ctrs,
diff --git a/arch/x86/oprofile/op_model_p4.c b/arch/x86/oprofile/op_model_p4.c
index 56b4757a1f47..e641545d4796 100644
--- a/arch/x86/oprofile/op_model_p4.c
+++ b/arch/x86/oprofile/op_model_p4.c
@@ -701,6 +701,8 @@ 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_hardware_counters = NUM_COUNTERS_HT2,
+        .num_hardware_controls = NUM_CONTROLS_HT2,
         .fill_in_addresses = &p4_fill_in_addresses,
         .setup_ctrs = &p4_setup_ctrs,
         .check_ctrs = &p4_check_ctrs,
@@ -713,6 +715,8 @@ 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_hardware_counters = NUM_COUNTERS_NON_HT,
+        .num_hardware_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 eff431f6c57b..e5811aa480eb 100644
--- a/arch/x86/oprofile/op_model_ppro.c
+++ b/arch/x86/oprofile/op_model_ppro.c
@@ -183,6 +183,8 @@ static void ppro_shutdown(struct op_msrs const * const msrs)
 struct op_x86_model_spec const op_ppro_spec = {
         .num_counters = NUM_COUNTERS,
         .num_controls = NUM_CONTROLS,
+        .num_hardware_counters = NUM_COUNTERS,
+        .num_hardware_controls = NUM_CONTROLS,
         .fill_in_addresses = &ppro_fill_in_addresses,
         .setup_ctrs = &ppro_setup_ctrs,
         .check_ctrs = &ppro_check_ctrs,
diff --git a/arch/x86/oprofile/op_x86_model.h b/arch/x86/oprofile/op_x86_model.h
index 05a0261ba0c3..e07ba1076371 100644
--- a/arch/x86/oprofile/op_x86_model.h
+++ b/arch/x86/oprofile/op_x86_model.h
@@ -19,6 +19,7 @@ struct op_saved_msr {
 struct op_msr {
         unsigned long addr;
         struct op_saved_msr saved;
+        struct op_saved_msr multiplex;
 };
 
 struct op_msrs {
@@ -34,6 +35,8 @@ struct pt_regs;
 struct op_x86_model_spec {
         int (*init)(struct oprofile_operations *ops);
         void (*exit)(void);
+        unsigned int const num_hardware_counters;
+        unsigned int const num_hardware_controls;
         unsigned int const num_counters;
         unsigned int const num_controls;
         void (*fill_in_addresses)(struct op_msrs * const msrs);
diff --git a/drivers/oprofile/oprof.c b/drivers/oprofile/oprof.c
index 2c645170f06e..b2fa5df64a62 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"
@@ -19,13 +21,18 @@
 #include "cpu_buffer.h"
 #include "buffer_sync.h"
 #include "oprofile_stats.h"
+
+static unsigned long is_setup;
+static void switch_worker(struct work_struct *work);
+static DECLARE_DELAYED_WORK(switch_work, switch_worker);
+static DEFINE_MUTEX(start_mutex);
  
 struct oprofile_operations oprofile_ops;
 
+unsigned long timeout_jiffies;
 unsigned long oprofile_started;
 unsigned long backtrace_depth;
-static unsigned long is_setup;
-static DEFINE_MUTEX(start_mutex);
+/* Multiplexing defaults at 1 msec*/
 
 /* timer
    0 - use performance monitoring hardware if available
@@ -87,6 +94,16 @@ out:
         return err;
 }
 
+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();
+}
 
 /* Actually start profiling (echo 1>/dev/oprofile/enable) */
 int oprofile_start(void)
@@ -94,7 +111,6 @@ int oprofile_start(void)
         int err = -EINVAL;
  
         mutex_lock(&start_mutex);
- 
         if (!is_setup)
                 goto out;
 
@@ -108,6 +124,9 @@ int oprofile_start(void)
         if ((err = oprofile_ops.start()))
                 goto out;
 
+        if (oprofile_ops.switch_events)
+                start_switch_worker();
+
         oprofile_started = 1;
 out:
         mutex_unlock(&start_mutex);
@@ -123,6 +142,7 @@ void oprofile_stop(void)
                 goto out;
         oprofile_ops.stop();
         oprofile_started = 0;
+        cancel_delayed_work_sync(&switch_work);
         /* wake up the daemon to read what remains */
         wake_up_buffer_waiter();
 out:
@@ -155,6 +175,32 @@ post_sync:
         mutex_unlock(&start_mutex);
 }
 
+/* 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(1);
+
+out:
+        mutex_unlock(&start_mutex);
+        return err;
+
+}
 
 int oprofile_set_backtrace(unsigned long val)
 {
@@ -179,10 +225,16 @@ out:
         return err;
 }
 
+static void __init oprofile_switch_timer_init(void)
+{
+        timeout_jiffies = msecs_to_jiffies(1);
+}
+
 static int __init oprofile_init(void)
 {
         int err;
 
+        oprofile_switch_timer_init();
         err = oprofile_arch_init(&oprofile_ops);
 
         if (err < 0 || timer) {
diff --git a/drivers/oprofile/oprof.h b/drivers/oprofile/oprof.h
index 18323650806e..c4406a7366bb 100644
--- a/drivers/oprofile/oprof.h
+++ b/drivers/oprofile/oprof.h
@@ -27,7 +27,8 @@ extern unsigned long fs_buffer_watershed;
 extern struct oprofile_operations oprofile_ops;
 extern unsigned long oprofile_started;
 extern unsigned long 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 ef953ba5ab6b..cc4f5a1f8ef2 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"
@@ -18,6 +19,40 @@ unsigned long fs_buffer_size = 131072;
 unsigned long fs_cpu_buffer_size = 8192;
 unsigned long fs_buffer_watershed = 32768; /* FIXME: tune */
 
+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,
+};
+
+
 static ssize_t depth_read(struct file * file, char __user * buf, size_t count, loff_t * offset)
 {
         return oprofilefs_ulong_to_user(backtrace_depth, buf, count, offset);
@@ -85,11 +120,10 @@ static ssize_t enable_write(struct file * file, char const __user * buf, size_t
 
         if (*offset)
                 return -EINVAL;
-
         retval = oprofilefs_ulong_from_user(&val, buf, count);
         if (retval)
                 return retval;
- 
+
         if (val)
                 retval = oprofile_start();
         else
@@ -129,6 +163,7 @@ 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);
+        oprofilefs_create_file(sb, root, "timeout_ms", &timeout_fops);
         oprofile_create_stats_files(sb, root);
         if (oprofile_ops.create_files)
                 oprofile_ops.create_files(sb, root);
diff --git a/include/linux/oprofile.h b/include/linux/oprofile.h
index bcb8f725427c..687f2f4c36a1 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;
 };