Re: [PATCH v2 3/6] rtla/utils: Add idle state disabling via libcpupower
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2024-07-31 15:41:03
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On Wed, 31 Jul 2024 10:36:52 +0200 tglozar@redhat.com wrote:
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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 | 140 +++++++++++++++++++++++++++++++++ tools/tracing/rtla/src/utils.h | 6 ++ 2 files changed, 146 insertions(+)diff --git a/tools/tracing/rtla/src/utils.c b/tools/tracing/rtla/src/utils.c index 9ac71a66840c..9279b8ce08c3 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>@@ -519,6 +522,143 @@ 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 *));
Need to check if the calloc failed and return an error if it did.
+ } + + saved_cpu_idle_disable_state[cpu] = calloc(nr_states, sizeof(unsigned int));
Here too.
+ 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;Hmm, should this warn if state is not zero and disabled is negative.
+ 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;
+Should probably have a check to see if saved_cpu_idle_disable exists.
+ nr_states = cpuidle_state_count(cpu); + + if (nr_states == 0) + return 0; +
As well as saved_cpu_idle_disable_state[cpu] exists. Just for robustness.
+ 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;
No need to check here. free() works fine with passing NULL to it. -- Steve
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+ 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 d44513e6c66a..51b6054c2679 100644 --- a/tools/tracing/rtla/src/utils.h +++ b/tools/tracing/rtla/src/utils.h@@ -64,6 +64,12 @@ 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); +#endif /* HAVE_LIBCPUPOWER_SUPPORT */ int auto_house_keeping(cpu_set_t *monitored_cpus); #define ns_to_usf(x) (((double)x/1000))