[PATCH v4 3/6] rtla/utils: Add idle state disabling via libcpupower

[tglozar]

From: Tomas Glozar <tglozar@xxxxxxxxxx>

Add functions to utils.c to disable idle states through functions of
libcpupower. This will serve as the basis for disabling idle states
per cpu when running timerlat.

Signed-off-by: Tomas Glozar <tglozar@xxxxxxxxxx>
---
 tools/tracing/rtla/src/utils.c | 150 +++++++++++++++++++++++++++++++++
 tools/tracing/rtla/src/utils.h |  13 +++
 2 files changed, 163 insertions(+)

diff --git a/tools/tracing/rtla/src/utils.c b/tools/tracing/rtla/src/utils.c
index 6fae234aaf36..4995d35cf3ec 100644
--- a/tools/tracing/rtla/src/utils.c
+++ b/tools/tracing/rtla/src/utils.c
@@ -4,6 +4,9 @@
  */
 
 #define _GNU_SOURCE
+#ifdef HAVE_LIBCPUPOWER_SUPPORT
+#include <cpuidle.h>
+#endif /* HAVE_LIBCPUPOWER_SUPPORT */
 #include <dirent.h>
 #include <stdarg.h>
 #include <stdlib.h>
@@ -515,6 +518,153 @@ int set_cpu_dma_latency(int32_t latency)
 	return fd;
 }
 
+#ifdef HAVE_LIBCPUPOWER_SUPPORT
+static unsigned int **saved_cpu_idle_disable_state;
+static size_t saved_cpu_idle_disable_state_alloc_ctr;
+
+/*
+ * save_cpu_idle_state_disable - save disable for all idle states of a cpu
+ *
+ * Saves the current disable of all idle states of a cpu, to be subsequently
+ * restored via restore_cpu_idle_disable_state.
+ *
+ * Return: idle state count on success, negative on error
+ */
+int save_cpu_idle_disable_state(unsigned int cpu)
+{
+	unsigned int nr_states;
+	unsigned int state;
+	int disabled;
+	int nr_cpus;
+
+	nr_states = cpuidle_state_count(cpu);
+
+	if (nr_states == 0)
+		return 0;
+
+	if (saved_cpu_idle_disable_state == NULL) {
+		nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
+		saved_cpu_idle_disable_state = calloc(nr_cpus, sizeof(unsigned int *));
+		if (!saved_cpu_idle_disable_state)
+			return -1;
+	}
+
+	saved_cpu_idle_disable_state[cpu] = calloc(nr_states, sizeof(unsigned int));
+	if (!saved_cpu_idle_disable_state[cpu])
+		return -1;
+	saved_cpu_idle_disable_state_alloc_ctr++;
+
+	for (state = 0; state < nr_states; state++) {
+		disabled = cpuidle_is_state_disabled(cpu, state);
+		if (disabled < 0)
+			return disabled;
+		saved_cpu_idle_disable_state[cpu][state] = disabled;
+	}
+
+	return nr_states;
+}
+
+/*
+ * restore_cpu_idle_disable_state - restore disable for all idle states of a cpu
+ *
+ * Restores the current disable state of all idle states of a cpu that was
+ * previously saved by save_cpu_idle_disable_state.
+ *
+ * Return: idle state count on success, negative on error
+ */
+int restore_cpu_idle_disable_state(unsigned int cpu)
+{
+	unsigned int nr_states;
+	unsigned int state;
+	int disabled;
+	int result;
+
+	nr_states = cpuidle_state_count(cpu);
+
+	if (nr_states == 0)
+		return 0;
+
+	if (!saved_cpu_idle_disable_state)
+		return -1;
+
+	for (state = 0; state < nr_states; state++) {
+		if (!saved_cpu_idle_disable_state[cpu])
+			return -1;
+		disabled = saved_cpu_idle_disable_state[cpu][state];
+		result = cpuidle_state_disable(cpu, state, disabled);
+		if (result < 0)
+			return result;
+	}
+
+	free(saved_cpu_idle_disable_state[cpu]);
+	saved_cpu_idle_disable_state[cpu] = NULL;
+	saved_cpu_idle_disable_state_alloc_ctr--;
+	if (saved_cpu_idle_disable_state_alloc_ctr == 0) {
+		free(saved_cpu_idle_disable_state);
+		saved_cpu_idle_disable_state = NULL;
+	}
+
+	return nr_states;
+}
+
+/*
+ * free_cpu_idle_disable_states - free saved idle state disable for all cpus
+ *
+ * Frees the memory used for storing cpu idle state disable for all cpus
+ * and states.
+ *
+ * Normally, the memory is freed automatically in
+ * restore_cpu_idle_disable_state; this is mostly for cleaning up after an
+ * error.
+ */
+void free_cpu_idle_disable_states(void)
+{
+	int cpu;
+	int nr_cpus;
+
+	if (!saved_cpu_idle_disable_state)
+		return;
+
+	nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
+
+	for (cpu = 0; cpu < nr_cpus; cpu++) {
+		free(saved_cpu_idle_disable_state[cpu]);
+		saved_cpu_idle_disable_state[cpu] = NULL;
+	}
+
+	free(saved_cpu_idle_disable_state);
+	saved_cpu_idle_disable_state = NULL;
+}
+
+/*
+ * set_deepest_cpu_idle_state - limit idle state of cpu
+ *
+ * Disables all idle states deeper than the one given in
+ * deepest_state (assuming states with higher number are deeper).
+ *
+ * This is used to reduce the exit from idle latency. Unlike
+ * set_cpu_dma_latency, it can disable idle states per cpu.
+ *
+ * Return: idle state count on success, negative on error
+ */
+int set_deepest_cpu_idle_state(unsigned int cpu, unsigned int deepest_state)
+{
+	unsigned int nr_states;
+	unsigned int state;
+	int result;
+
+	nr_states = cpuidle_state_count(cpu);
+
+	for (state = deepest_state + 1; state < nr_states; state++) {
+		result = cpuidle_state_disable(cpu, state, 1);
+		if (result < 0)
+			return result;
+	}
+
+	return nr_states;
+}
+#endif /* HAVE_LIBCPUPOWER_SUPPORT */
+
 #define _STR(x) #x
 #define STR(x) _STR(x)
 
diff --git a/tools/tracing/rtla/src/utils.h b/tools/tracing/rtla/src/utils.h
index 99c9cf81bcd0..101d4799a009 100644
--- a/tools/tracing/rtla/src/utils.h
+++ b/tools/tracing/rtla/src/utils.h
@@ -66,6 +66,19 @@ int set_comm_sched_attr(const char *comm_prefix, struct sched_attr *attr);
 int set_comm_cgroup(const char *comm_prefix, const char *cgroup);
 int set_pid_cgroup(pid_t pid, const char *cgroup);
 int set_cpu_dma_latency(int32_t latency);
+#ifdef HAVE_LIBCPUPOWER_SUPPORT
+int save_cpu_idle_disable_state(unsigned int cpu);
+int restore_cpu_idle_disable_state(unsigned int cpu);
+void free_cpu_idle_disable_states(void);
+int set_deepest_cpu_idle_state(unsigned int cpu, unsigned int state);
+static inline int have_libcpupower_support(void) { return 1; }
+#else
+static inline int save_cpu_idle_disable_state(unsigned int cpu) { return -1; }
+static inline int restore_cpu_idle_disable_state(unsigned int cpu) { return -1; }
+static inline void free_cpu_idle_disable_states(void) { }
+static inline int set_deepest_cpu_idle_state(unsigned int cpu, unsigned int state) { return -1; }
+static inline int have_libcpupower_support(void) { return 0; }
+#endif /* HAVE_LIBCPUPOWER_SUPPORT */
 int auto_house_keeping(cpu_set_t *monitored_cpus);
 
 #define ns_to_usf(x) (((double)x/1000))
-- 
2.47.0