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authorTim Chen <tim.c.chen@linux.intel.com>2016-11-22 12:23:56 -0800
committerThomas Gleixner <tglx@linutronix.de>2016-11-24 20:44:19 +0100
commitf9793e34952cda133caaa35738a4b46053331c96 (patch)
tree190366f26441bc5f2f06119cf8510c6dea2a909b
parent5e76b2ab36b40ca33023e78725bdc69eafd63134 (diff)
downloadlinux-f9793e34952cda133caaa35738a4b46053331c96.tar.bz2
x86/sysctl: Add sysctl for ITMT scheduling feature
Intel Turbo Boost Max Technology 3.0 (ITMT) feature allows some cores to be boosted to higher turbo frequency than others. Add /proc/sys/kernel/sched_itmt_enabled so operator can enable/disable scheduling of tasks that favor cores with higher turbo boost frequency potential. By default, system that is ITMT capable and single socket has this feature turned on. It is more likely to be lightly loaded and operates in Turbo range. When there is a change in the ITMT scheduling operation desired, a rebuild of the sched domain is initiated so the scheduler can set up sched domains with appropriate flag to enable/disable ITMT scheduling operations. Co-developed-by: Peter Zijlstra (Intel) <peterz@infradead.org> Co-developed-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Cc: linux-pm@vger.kernel.org Cc: peterz@infradead.org Cc: jolsa@redhat.com Cc: rjw@rjwysocki.net Cc: linux-acpi@vger.kernel.org Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Cc: bp@suse.de Link: http://lkml.kernel.org/r/07cc62426a28bad57b01ab16bb903a9c84fa5421.1479844244.git.tim.c.chen@linux.intel.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
-rw-r--r--arch/x86/include/asm/topology.h7
-rw-r--r--arch/x86/kernel/itmt.c108
2 files changed, 112 insertions, 3 deletions
diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
index 8ace9511347c..4813df5c21f0 100644
--- a/arch/x86/include/asm/topology.h
+++ b/arch/x86/include/asm/topology.h
@@ -152,23 +152,26 @@ extern bool x86_topology_update;
#include <asm/percpu.h>
DECLARE_PER_CPU_READ_MOSTLY(int, sched_core_priority);
+extern unsigned int __read_mostly sysctl_sched_itmt_enabled;
/* Interface to set priority of a cpu */
void sched_set_itmt_core_prio(int prio, int core_cpu);
/* Interface to notify scheduler that system supports ITMT */
-void sched_set_itmt_support(void);
+int sched_set_itmt_support(void);
/* Interface to notify scheduler that system revokes ITMT support */
void sched_clear_itmt_support(void);
#else /* CONFIG_SCHED_ITMT */
+#define sysctl_sched_itmt_enabled 0
static inline void sched_set_itmt_core_prio(int prio, int core_cpu)
{
}
-static inline void sched_set_itmt_support(void)
+static inline int sched_set_itmt_support(void)
{
+ return 0;
}
static inline void sched_clear_itmt_support(void)
{
diff --git a/arch/x86/kernel/itmt.c b/arch/x86/kernel/itmt.c
index 63c9b3e3509d..672fbf7df2a4 100644
--- a/arch/x86/kernel/itmt.c
+++ b/arch/x86/kernel/itmt.c
@@ -34,6 +34,68 @@ DEFINE_PER_CPU_READ_MOSTLY(int, sched_core_priority);
/* Boolean to track if system has ITMT capabilities */
static bool __read_mostly sched_itmt_capable;
+/*
+ * Boolean to control whether we want to move processes to cpu capable
+ * of higher turbo frequency for cpus supporting Intel Turbo Boost Max
+ * Technology 3.0.
+ *
+ * It can be set via /proc/sys/kernel/sched_itmt_enabled
+ */
+unsigned int __read_mostly sysctl_sched_itmt_enabled;
+
+static int sched_itmt_update_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos)
+{
+ unsigned int old_sysctl;
+ int ret;
+
+ mutex_lock(&itmt_update_mutex);
+
+ if (!sched_itmt_capable) {
+ mutex_unlock(&itmt_update_mutex);
+ return -EINVAL;
+ }
+
+ old_sysctl = sysctl_sched_itmt_enabled;
+ ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+
+ if (!ret && write && old_sysctl != sysctl_sched_itmt_enabled) {
+ x86_topology_update = true;
+ rebuild_sched_domains();
+ }
+
+ mutex_unlock(&itmt_update_mutex);
+
+ return ret;
+}
+
+static unsigned int zero;
+static unsigned int one = 1;
+static struct ctl_table itmt_kern_table[] = {
+ {
+ .procname = "sched_itmt_enabled",
+ .data = &sysctl_sched_itmt_enabled,
+ .maxlen = sizeof(unsigned int),
+ .mode = 0644,
+ .proc_handler = sched_itmt_update_handler,
+ .extra1 = &zero,
+ .extra2 = &one,
+ },
+ {}
+};
+
+static struct ctl_table itmt_root_table[] = {
+ {
+ .procname = "kernel",
+ .mode = 0555,
+ .child = itmt_kern_table,
+ },
+ {}
+};
+
+static struct ctl_table_header *itmt_sysctl_header;
+
/**
* sched_set_itmt_support() - Indicate platform supports ITMT
*
@@ -45,14 +107,39 @@ static bool __read_mostly sched_itmt_capable;
*
* This must be done only after sched_set_itmt_core_prio
* has been called to set the cpus' priorities.
+ * It must not be called with cpu hot plug lock
+ * held as we need to acquire the lock to rebuild sched domains
+ * later.
+ *
+ * Return: 0 on success
*/
-void sched_set_itmt_support(void)
+int sched_set_itmt_support(void)
{
mutex_lock(&itmt_update_mutex);
+ if (sched_itmt_capable) {
+ mutex_unlock(&itmt_update_mutex);
+ return 0;
+ }
+
+ itmt_sysctl_header = register_sysctl_table(itmt_root_table);
+ if (!itmt_sysctl_header) {
+ mutex_unlock(&itmt_update_mutex);
+ return -ENOMEM;
+ }
+
sched_itmt_capable = true;
+ sysctl_sched_itmt_enabled = 1;
+
+ if (sysctl_sched_itmt_enabled) {
+ x86_topology_update = true;
+ rebuild_sched_domains();
+ }
+
mutex_unlock(&itmt_update_mutex);
+
+ return 0;
}
/**
@@ -61,13 +148,32 @@ void sched_set_itmt_support(void)
* This function is used by the OS to indicate that it has
* revoked the platform's support of ITMT feature.
*
+ * It must not be called with cpu hot plug lock
+ * held as we need to acquire the lock to rebuild sched domains
+ * later.
*/
void sched_clear_itmt_support(void)
{
mutex_lock(&itmt_update_mutex);
+ if (!sched_itmt_capable) {
+ mutex_unlock(&itmt_update_mutex);
+ return;
+ }
sched_itmt_capable = false;
+ if (itmt_sysctl_header) {
+ unregister_sysctl_table(itmt_sysctl_header);
+ itmt_sysctl_header = NULL;
+ }
+
+ if (sysctl_sched_itmt_enabled) {
+ /* disable sched_itmt if we are no longer ITMT capable */
+ sysctl_sched_itmt_enabled = 0;
+ x86_topology_update = true;
+ rebuild_sched_domains();
+ }
+
mutex_unlock(&itmt_update_mutex);
}