[PATCH]new ACPI processor driver to force CPUs idle

Shaohua Li
2009-06-24T04:13:53Z

This patch supports the processor aggregator device. When OS gets one ACPI
notification, the driver will idle some number of cpus.

To make CPU idle, the patch will create power saving thread. Scheduler
will migrate the thread to preferred CPU. The thread has max priority and
has SCHED_RR policy, so it can occupy one CPU. To save power, the thread will
keep calling C-state instruction. Routine power_saving_thread() is the entry
of the thread.

To avoid starvation, the thread will sleep 5% time for every second
(current RT scheduler has threshold to avoid starvation, but if other
CPUs are idle, the CPU can borrow CPU timer from other, so makes the mechanism
not work here)

This approach (to force CPU idle) should hasn't impact to scheduler and tasks
with affinity still can get chance to run even the tasks run on idled cpu. Any
comments/suggestions are welcome.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
---
drivers/acpi/Kconfig | 11 +
drivers/acpi/Makefile | 2
drivers/acpi/processor_aggregator.c | 389 ++++++++++++++++++++++++++++++++++++
3 files changed, 402 insertions(+)

Index: linux/drivers/acpi/Kconfig
===================================================================
--- linux.orig/drivers/acpi/Kconfig 2009-06-23 15:34:33.000000000 +0800
+++ linux/drivers/acpi/Kconfig 2009-06-23 15:52:53.000000000 +0800
@@ -196,6 +196,17 @@ config ACPI_HOTPLUG_CPU
select ACPI_CONTAINER
default y

+config ACPI_PROCESSOR_AGGREGATOR
+ tristate "Processor Aggregator"
+ depends on ACPI_PROCESSOR
+ depends on EXPERIMENTAL
+ help
+ ACPI 4.0 defines processor Aggregator, which enables OS to perform
+ specfic processor configuration and control that applies to all
+ processors in the platform. Currently only logical processor idling
+ is defined, which is to reduce power consumption. This driver
+ support the new device.
+
config ACPI_THERMAL
tristate "Thermal Zone"
depends on ACPI_PROCESSOR
Index: linux/drivers/acpi/Makefile
===================================================================
--- linux.orig/drivers/acpi/Makefile 2009-06-23 15:34:33.000000000 +0800
+++ linux/drivers/acpi/Makefile 2009-06-23 15:52:53.000000000 +0800
@@ -61,3 +61,5 @@ obj-$(CONFIG_ACPI_SBS) += sbs.o
processor-y := processor_core.o processor_throttling.o
processor-y += processor_idle.o processor_thermal.o
processor-$(CONFIG_CPU_FREQ) += processor_perflib.o
+
+obj-$(CONFIG_ACPI_PROCESSOR_AGGREGATOR) += processor_aggregator.o
Index: linux/drivers/acpi/processor_aggregator.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux/drivers/acpi/processor_aggregator.c 2009-06-24 11:58:33.000000000 +0800
@@ -0,0 +1,389 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at
+ * your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+#include <linux/kernel.h>
+#include <linux/cpumask.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/kthread.h>
+#include <linux/freezer.h>
+#include <linux/cpu.h>
+#include <linux/clockchips.h>
+#include <acpi/acpi_bus.h>
+#include <acpi/acpi_drivers.h>
+
+#define ACPI_PROCESSOR_AGGREGATOR_CLASS "processor_aggregator"
+#define ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME "Processor Aggregator"
+#define ACPI_PROCESSOR_AGGREGATOR_NOTIFY 0x80
+static DEFINE_MUTEX(isolated_cpus_lock);
+
+#define MWAIT_SUBSTATE_MASK (0xf)
+#define MWAIT_CSTATE_MASK (0xf)
+#define MWAIT_SUBSTATE_SIZE (4)
+#define CPUID_MWAIT_LEAF (5)
+#define CPUID5_ECX_EXTENSIONS_SUPPORTED (0x1)
+#define CPUID5_ECX_INTERRUPT_BREAK (0x2)
+static unsigned long power_saving_mwait_eax;
+static void power_saving_mwait_init(void)
+{
+ unsigned int eax, ebx, ecx, edx;
+ unsigned int highest_cstate = 0;
+ unsigned int highest_subcstate = 0;
+ int i;
+
+ if (!boot_cpu_has(X86_FEATURE_MWAIT))
+ return;
+ if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
+ return;
+
+ cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
+
+ if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
+ !(ecx & CPUID5_ECX_INTERRUPT_BREAK))
+ return;
+
+ edx >>= MWAIT_SUBSTATE_SIZE;
+ for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) {
+ if (edx & MWAIT_SUBSTATE_MASK) {
+ highest_cstate = i;
+ highest_subcstate = edx & MWAIT_SUBSTATE_MASK;
+ }
+ }
+ power_saving_mwait_eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) |
+ (highest_subcstate - 1);
+
+ for_each_online_cpu(i)
+ clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ON, &i);
+
+#if defined (CONFIG_GENERIC_TIME) && defined (CONFIG_X86)
+ switch (boot_cpu_data.x86_vendor) {
+ case X86_VENDOR_AMD:
+ case X86_VENDOR_INTEL:
+ /*
+ * AMD Fam10h TSC will tick in all
+ * C/P/S0/S1 states when this bit is set.
+ */
+ if (boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
+ return;
+
+ /*FALL THROUGH*/
+ default:
+ /* TSC could halt in idle, so notify users */
+ mark_tsc_unstable("TSC halts in idle");
+ }
+#endif
+}
+
+static int power_saving_thread(void *data)
+{
+ struct sched_param param = {.sched_priority = MAX_RT_PRIO - 1};
+ int do_sleep;
+
+ /*
+ * we just create a RT task to do power saving. Scheduler will migrate
+ * the task to any CPU.
+ */
+ sched_setscheduler(current, SCHED_RR, &param);
+
+ while (!kthread_should_stop()) {
+ int cpu;
+ u64 expire_time;
+
+ try_to_freeze();
+
+ do_sleep = 0;
+
+ current_thread_info()->status &= ~TS_POLLING;
+ /*
+ * TS_POLLING-cleared state must be visible before we test
+ * NEED_RESCHED:
+ */
+ smp_mb();
+
+ expire_time = jiffies + HZ * 95 /100;
+
+ while (!need_resched()) {
+ local_irq_disable();
+ cpu = smp_processor_id();
+ clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
+ stop_critical_timings();
+
+ __monitor((void *)&current_thread_info()->flags, 0, 0);
+ smp_mb();
+ if (!need_resched())
+ __mwait(power_saving_mwait_eax, 1);
+
+ start_critical_timings();
+ clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
+ local_irq_enable();
+
+ if (jiffies > expire_time) {
+ do_sleep = 1;
+ break;
+ }
+ }
+
+ current_thread_info()->status |= TS_POLLING;
+
+ /*
+ * current sched_rt has threshold for rt task running time.
+ * When a rt task uses 95% CPU time, the rt thread will be
+ * scheduled out for 5% CPU time to not starve other tasks. But
+ * the mechanism only works when all CPUs have RT task running,
+ * as if one CPU hasn't RT task, RT task from other CPUs will
+ * borrow CPU time from this CPU and cause RT task use > 95%
+ * CPU time. To make 'avoid staration' work, takes a nap here.
+ */
+ if (do_sleep)
+ schedule_timeout_killable(HZ * 5 /100);
+ }
+ return 0;
+}
+
+static struct task_struct *ps_tsks[NR_CPUS];
+static unsigned int ps_tsk_num;
+static int create_power_saving_task(void)
+{
+ ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread, NULL,
+ "power_saving/%d", ps_tsk_num);
+ if (ps_tsks[ps_tsk_num]) {
+ ps_tsk_num++;
+ return 0;
+ }
+ return -EINVAL;
+}
+
+static void destroy_power_saving_task(void)
+{
+ if (ps_tsk_num > 0) {
+ ps_tsk_num--;
+ kthread_stop(ps_tsks[ps_tsk_num]);
+ }
+}
+
+static void set_power_saving_task_num(unsigned int num)
+{
+ if (num > ps_tsk_num) {
+ while (ps_tsk_num < num) {
+ if (create_power_saving_task())
+ return;
+ }
+ } else if (num < ps_tsk_num) {
+ while (ps_tsk_num > num)
+ destroy_power_saving_task();
+ }
+}
+
+static int acpi_processor_aggregator_idle_cpus(unsigned int num_cpus)
+{
+ get_online_cpus();
+
+ num_cpus = min_t(unsigned int, num_cpus, num_online_cpus());
+ set_power_saving_task_num(num_cpus);
+
+ put_online_cpus();
+ return 0;
+}
+
+static uint32_t acpi_processor_aggregator_idle_cpus_num(void)
+{
+ return ps_tsk_num;
+}
+
+static ssize_t acpi_processor_aggregator_idlecpus_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t count)
+{
+ unsigned long num;
+ if (strict_strtoul(buf, 0, &num))
+ return -EINVAL;
+ mutex_lock(&isolated_cpus_lock);
+ acpi_processor_aggregator_idle_cpus(num);
+ mutex_unlock(&isolated_cpus_lock);
+ return count;
+}
+
+static ssize_t acpi_processor_aggregator_idlecpus_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ return scnprintf(buf, PAGE_SIZE, "%d",
+ acpi_processor_aggregator_idle_cpus_num());
+}
+static DEVICE_ATTR(idlecpus, S_IRUGO|S_IWUSR,
+ acpi_processor_aggregator_idlecpus_show,
+ acpi_processor_aggregator_idlecpus_store);
+
+static int acpi_processor_aggregator_add_sysfs(struct acpi_device *device)
+{
+ int result;
+
+ result = device_create_file(&device->dev, &dev_attr_idlecpus);
+ if (result)
+ return -ENODEV;
+ return 0;
+}
+
+static void acpi_processor_aggregator_remove_sysfs(struct acpi_device *device)
+{
+ device_remove_file(&device->dev, &dev_attr_idlecpus);
+}
+
+/* Query firmware how many CPUs should be idle */
+static int acpi_processor_aggregator_pur(acpi_handle handle, int *num_cpus)
+{
+ struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
+ acpi_status status;
+ union acpi_object *package;
+ int rev, num, ret = -EINVAL;
+
+ status = acpi_evaluate_object(handle, "_PUR", NULL, &buffer);
+ if (ACPI_FAILURE(status))
+ return -EINVAL;
+ package = buffer.pointer;
+ if (package->type != ACPI_TYPE_PACKAGE || package->package.count != 2)
+ goto out;
+ rev = package->package.elements[0].integer.value;
+ num = package->package.elements[1].integer.value;
+ if (rev != 1)
+ goto out;
+ *num_cpus = num;
+ ret = 0;
+out:
+ kfree(buffer.pointer);
+ return ret;
+}
+
+/* Notify firmware how many CPUs are idle */
+static void acpi_processor_aggregator_ost(acpi_handle handle, int stat,
+ uint32_t idle_cpus)
+{
+ union acpi_object params[3] = {
+ {.type = ACPI_TYPE_INTEGER,},
+ {.type = ACPI_TYPE_INTEGER,},
+ {.type = ACPI_TYPE_BUFFER,},
+ };
+ struct acpi_object_list arg_list = {3, params};
+
+ params[0].integer.value = ACPI_PROCESSOR_AGGREGATOR_NOTIFY;
+ params[1].integer.value = stat;
+ params[2].buffer.length = 4;
+ params[2].buffer.pointer = (void *)&idle_cpus;
+ acpi_evaluate_object(handle, "_OST", &arg_list, NULL);
+}
+
+static void acpi_processor_aggregator_handle_notify(acpi_handle handle)
+{
+ int num_cpus, ret;
+ uint32_t idle_cpus;
+
+ mutex_lock(&isolated_cpus_lock);
+ if (acpi_processor_aggregator_pur(handle, &num_cpus)) {
+ mutex_unlock(&isolated_cpus_lock);
+ return;
+ }
+ ret = acpi_processor_aggregator_idle_cpus(num_cpus);
+ idle_cpus = acpi_processor_aggregator_idle_cpus_num();
+ if (!ret)
+ acpi_processor_aggregator_ost(handle, 0, idle_cpus);
+ else
+ acpi_processor_aggregator_ost(handle, 1, 0);
+ mutex_unlock(&isolated_cpus_lock);
+}
+
+static void acpi_processor_aggregator_notify(acpi_handle handle, u32 event,
+ void *data)
+{
+ struct acpi_device *device = data;
+
+ switch (event) {
+ case ACPI_PROCESSOR_AGGREGATOR_NOTIFY:
+ acpi_processor_aggregator_handle_notify(handle);
+ acpi_bus_generate_proc_event(device, event, 0);
+ acpi_bus_generate_netlink_event(device->pnp.device_class,
+ dev_name(&device->dev), event, 0);
+ break;
+ default:
+ printk(KERN_WARNING"Unsupported event [0x%x]\n", event);
+ break;
+ }
+}
+
+static int acpi_processor_aggregator_add(struct acpi_device *device)
+{
+ acpi_status status;
+
+ strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME);
+ strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS);
+
+ if (acpi_processor_aggregator_add_sysfs(device))
+ return -ENODEV;
+
+ status = acpi_install_notify_handler(device->handle,
+ ACPI_DEVICE_NOTIFY, acpi_processor_aggregator_notify, device);
+ if (ACPI_FAILURE(status)) {
+ acpi_processor_aggregator_remove_sysfs(device);
+ return -ENODEV;
+ }
+
+ return 0;
+}
+
+static int acpi_processor_aggregator_remove(struct acpi_device *device, int type)
+{
+ mutex_lock(&isolated_cpus_lock);
+ acpi_processor_aggregator_idle_cpus(0);
+ mutex_unlock(&isolated_cpus_lock);
+
+ acpi_remove_notify_handler(device->handle,
+ ACPI_DEVICE_NOTIFY, acpi_processor_aggregator_notify);
+ acpi_processor_aggregator_remove_sysfs(device);
+ return 0;
+}
+
+static const struct acpi_device_id processor_aggregator_device_ids[] = {
+ {"ACPI000C", 0},
+ {"", 0},
+};
+MODULE_DEVICE_TABLE(acpi, processor_aggregator_device_ids);
+
+static struct acpi_driver acpi_processor_aggregator_driver = {
+ .name = "processor_aggregator",
+ .class = ACPI_PROCESSOR_AGGREGATOR_CLASS,
+ .ids = processor_aggregator_device_ids,
+ .ops = {
+ .add = acpi_processor_aggregator_add,
+ .remove = acpi_processor_aggregator_remove,
+ },
+};
+
+static int __init acpi_processor_aggregator_init(void)
+{
+ power_saving_mwait_init();
+ if (power_saving_mwait_eax == 0)
+ return -EINVAL;
+
+ return acpi_bus_register_driver(&acpi_processor_aggregator_driver);
+}
+
+static void __exit acpi_processor_aggregator_exit(void)
+{
+ acpi_bus_unregister_driver(&acpi_processor_aggregator_driver);
+}
+
+module_init(acpi_processor_aggregator_init);
+module_exit(acpi_processor_aggregator_exit);
+MODULE_AUTHOR("Shaohua Li<shaohua.li@intel.com>");
+MODULE_DESCRIPTION("ACPI Processor Aggregator Driver");
+MODULE_LICENSE("GPL");