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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 /arch/x86/kernel/itmt.c
parent5e76b2ab36b40ca33023e78725bdc69eafd63134 (diff)
downloadtalos-obmc-linux-f9793e34952cda133caaa35738a4b46053331c96.tar.gz
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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>
Diffstat (limited to 'arch/x86/kernel/itmt.c')
-rw-r--r--arch/x86/kernel/itmt.c108
1 files changed, 107 insertions, 1 deletions
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);
}
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