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From: tglozar@redhat.com
To: bristot@kernel.org,
	rostedt@goodmis.org
Cc: linux-trace-kernel@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	jkacur@redhat.com,
	jwyatt@redhat.com,
	Tomas Glozar <tglozar@redhat.com>
Subject: [PATCH 2/5] rtla/utils: Add idle state disabling via libcpupower
Date: Wed, 12 Jun 2024 16:54:36 +0200
Message-ID: <20240612145439.206990-3-tglozar@redhat.com>
In-Reply-To: <20240612145439.206990-1-tglozar@redhat.com>
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From: Tomas Glozar <tglozar@redhat.com>

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@redhat.com>
---
 tools/tracing/rtla/src/utils.c | 133 +++++++++++++++++++++++++++++++++
 tools/tracing/rtla/src/utils.h |   4 +
 2 files changed, 137 insertions(+)

diff --git a/tools/tracing/rtla/src/utils.c b/tools/tracing/rtla/src/utils.c
index 9ac71a66840c..638c50f0f88e 100644
--- a/tools/tracing/rtla/src/utils.c
+++ b/tools/tracing/rtla/src/utils.c
@@ -4,6 +4,7 @@
  */
 
 #define _GNU_SOURCE
+#include <cpuidle.h>
 #include <dirent.h>
 #include <stdarg.h>
 #include <stdlib.h>
@@ -519,6 +520,138 @@ int set_cpu_dma_latency(int32_t latency)
 	return fd;
 }
 
+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 *));
+	}
+
+	saved_cpu_idle_disable_state[cpu] = calloc(nr_states, sizeof(unsigned int));
+	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;
+
+	for (state = 0; state < nr_states; state++) {
+		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;
+
+	if (!saved_cpu_idle_disable_state)
+		return;
+
+	for (cpu = 0; cpu < sysconf(_SC_NPROCESSORS_CONF); cpu++) {
+		if (!saved_cpu_idle_disable_state[cpu])
+			continue;
+		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_cpu_idle_disable_state - set disable for all idle states of a cpu
+ *
+ * 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_cpu_idle_disable_state(unsigned int cpu, unsigned int disable)
+{
+	unsigned int nr_states;
+	unsigned int state;
+	int result;
+
+	nr_states = cpuidle_state_count(cpu);
+
+	for (state = 0; state < nr_states; state++) {
+		result = cpuidle_state_disable(cpu, state, disable);
+		if (result < 0)
+			return result;
+	}
+
+	return nr_states;
+}
+
 #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 d44513e6c66a..b310ed5cd867 100644
--- a/tools/tracing/rtla/src/utils.h
+++ b/tools/tracing/rtla/src/utils.h
@@ -64,6 +64,10 @@ 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);
+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_cpu_idle_disable_state(unsigned int cpu, unsigned int disable);
 int auto_house_keeping(cpu_set_t *monitored_cpus);
 
 #define ns_to_usf(x) (((double)x/1000))
-- 
2.43.0