[v8,1/2] power: introduce PM QoS API on CPU wide

Message ID 20240709072518.4225-2-lihuisong@huawei.com (mailing list archive)
State New
Delegated to: Thomas Monjalon
Headers
Series power: introduce PM QoS interface |

Checks

Context Check Description
ci/checkpatch success coding style OK

Commit Message

lihuisong (C) July 9, 2024, 7:25 a.m. UTC
  The deeper the idle state, the lower the power consumption, but the longer
the resume time. Some service are delay sensitive and very except the low
resume time, like interrupt packet receiving mode.

And the "/sys/devices/system/cpu/cpuX/power/pm_qos_resume_latency_us" sysfs
interface is used to set and get the resume latency limit on the cpuX for
userspace. Each cpuidle governor in Linux select which idle state to enter
based on this CPU resume latency in their idle task.

The per-CPU PM QoS API can be used to control this CPU's idle state
selection and limit just enter the shallowest idle state to low the delay
after sleep by setting strict resume latency (zero value).

Signed-off-by: Huisong Li <lihuisong@huawei.com>
Acked-by: Morten Brørup <mb@smartsharesystems.com>
---
 doc/guides/prog_guide/power_man.rst    |  24 ++++++
 doc/guides/rel_notes/release_24_07.rst |   4 +
 lib/power/meson.build                  |   2 +
 lib/power/rte_power_qos.c              | 114 +++++++++++++++++++++++++
 lib/power/rte_power_qos.h              |  73 ++++++++++++++++
 lib/power/version.map                  |   2 +
 6 files changed, 219 insertions(+)
 create mode 100644 lib/power/rte_power_qos.c
 create mode 100644 lib/power/rte_power_qos.h
  

Patch

diff --git a/doc/guides/prog_guide/power_man.rst b/doc/guides/prog_guide/power_man.rst
index f6674efe2d..faa32b4320 100644
--- a/doc/guides/prog_guide/power_man.rst
+++ b/doc/guides/prog_guide/power_man.rst
@@ -249,6 +249,30 @@  Get Num Pkgs
 Get Num Dies
   Get the number of die's on a given package.
 
+
+PM QoS
+------
+
+The deeper the idle state, the lower the power consumption, but the longer
+the resume time. Some service are delay sensitive and very except the low
+resume time, like interrupt packet receiving mode.
+
+And the "/sys/devices/system/cpu/cpuX/power/pm_qos_resume_latency_us" sysfs
+interface is used to set and get the resume latency limit on the cpuX for
+userspace. Each cpuidle governor in Linux select which idle state to enter
+based on this CPU resume latency in their idle task.
+
+The per-CPU PM QoS API can be used to set and get the CPU resume latency based
+on this sysfs.
+
+The ``rte_power_qos_set_cpu_resume_latency()`` function can control the CPU's
+idle state selection in Linux and limit just to enter the shallowest idle state
+to low the delay of resuming service after sleeping by setting strict resume
+latency (zero value).
+
+The ``rte_power_qos_get_cpu_resume_latency()`` function can get the resume
+latency on specified CPU.
+
 References
 ----------
 
diff --git a/doc/guides/rel_notes/release_24_07.rst b/doc/guides/rel_notes/release_24_07.rst
index 50ffc1f74a..e771868d9f 100644
--- a/doc/guides/rel_notes/release_24_07.rst
+++ b/doc/guides/rel_notes/release_24_07.rst
@@ -156,6 +156,10 @@  New Features
   * Added defer queue reclamation via RCU.
   * Added SVE support for bulk lookup.
 
+* **Introduce per-CPU PM QoS interface.**
+
+  * Introduce per-CPU PM QoS interface to low the delay after sleep.
+
 
 Removed Items
 -------------
diff --git a/lib/power/meson.build b/lib/power/meson.build
index b8426589b2..8222e178b0 100644
--- a/lib/power/meson.build
+++ b/lib/power/meson.build
@@ -23,12 +23,14 @@  sources = files(
         'rte_power.c',
         'rte_power_uncore.c',
         'rte_power_pmd_mgmt.c',
+        'rte_power_qos.c',
 )
 headers = files(
         'rte_power.h',
         'rte_power_guest_channel.h',
         'rte_power_pmd_mgmt.h',
         'rte_power_uncore.h',
+        'rte_power_qos.h',
 )
 if cc.has_argument('-Wno-cast-qual')
     cflags += '-Wno-cast-qual'
diff --git a/lib/power/rte_power_qos.c b/lib/power/rte_power_qos.c
new file mode 100644
index 0000000000..375746f832
--- /dev/null
+++ b/lib/power/rte_power_qos.c
@@ -0,0 +1,114 @@ 
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2024 HiSilicon Limited
+ */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <rte_lcore.h>
+#include <rte_log.h>
+
+#include "power_common.h"
+#include "rte_power_qos.h"
+
+#define PM_QOS_SYSFILE_RESUME_LATENCY_US	\
+	"/sys/devices/system/cpu/cpu%u/power/pm_qos_resume_latency_us"
+
+int
+rte_power_qos_set_cpu_resume_latency(uint16_t lcore_id, int latency)
+{
+	char buf[LINE_MAX];
+	FILE *f;
+	int ret;
+
+	if (!rte_lcore_is_enabled(lcore_id)) {
+		POWER_LOG(ERR, "lcore id %u is not enabled", lcore_id);
+		return -EINVAL;
+	}
+
+	if (latency < 0) {
+		POWER_LOG(ERR, "latency should be greater than and equal to 0");
+		return -EINVAL;
+	}
+
+	ret = open_core_sysfs_file(&f, "w", PM_QOS_SYSFILE_RESUME_LATENCY_US, lcore_id);
+	if (ret != 0) {
+		POWER_LOG(ERR, "Failed to open "PM_QOS_SYSFILE_RESUME_LATENCY_US, lcore_id);
+		return ret;
+	}
+
+	/*
+	 * Based on the sysfs interface pm_qos_resume_latency_us under
+	 * @PM_QOS_SYSFILE_RESUME_LATENCY_US directory in kernel, their meanning
+	 * is as follows for different input string.
+	 * 1> the resume latency is 0 if the input is "n/a".
+	 * 2> the resume latency is no constraint if the input is "0".
+	 * 3> the resume latency is the actual value to be set.
+	 */
+	if (latency == 0)
+		snprintf(buf, sizeof(buf), "%s", "n/a");
+	else if (latency == RTE_POWER_QOS_RESUME_LATENCY_NO_CONSTRAINT)
+		snprintf(buf, sizeof(buf), "%u", 0);
+	else
+		snprintf(buf, sizeof(buf), "%u", latency);
+
+	ret = write_core_sysfs_s(f, buf);
+	if (ret != 0) {
+		POWER_LOG(ERR, "Failed to write "PM_QOS_SYSFILE_RESUME_LATENCY_US, lcore_id);
+		goto out;
+	}
+
+out:
+	if (f != NULL)
+		fclose(f);
+
+	return ret;
+}
+
+int
+rte_power_qos_get_cpu_resume_latency(uint16_t lcore_id)
+{
+	char buf[LINE_MAX];
+	int latency = -1;
+	FILE *f;
+	int ret;
+
+	if (!rte_lcore_is_enabled(lcore_id)) {
+		POWER_LOG(ERR, "lcore id %u is not enabled", lcore_id);
+		return -EINVAL;
+	}
+
+	ret = open_core_sysfs_file(&f, "r", PM_QOS_SYSFILE_RESUME_LATENCY_US, lcore_id);
+	if (ret != 0) {
+		POWER_LOG(ERR, "Failed to open "PM_QOS_SYSFILE_RESUME_LATENCY_US, lcore_id);
+		return ret;
+	}
+
+	ret = read_core_sysfs_s(f, buf, sizeof(buf));
+	if (ret != 0) {
+		POWER_LOG(ERR, "Failed to read "PM_QOS_SYSFILE_RESUME_LATENCY_US, lcore_id);
+		goto out;
+	}
+
+	/*
+	 * Based on the sysfs interface pm_qos_resume_latency_us under
+	 * @PM_QOS_SYSFILE_RESUME_LATENCY_US directory in kernel, their meanning
+	 * is as follows for different output string.
+	 * 1> the resume latency is 0 if the output is "n/a".
+	 * 2> the resume latency is no constraint if the output is "0".
+	 * 3> the resume latency is the actual value in used for other string.
+	 */
+	if (strcmp(buf, "n/a") == 0)
+		latency = 0;
+	else {
+		latency = strtoul(buf, NULL, 10);
+		latency = latency == 0 ? RTE_POWER_QOS_RESUME_LATENCY_NO_CONSTRAINT : latency;
+	}
+
+out:
+	if (f != NULL)
+		fclose(f);
+
+	return latency != -1 ? latency : ret;
+}
diff --git a/lib/power/rte_power_qos.h b/lib/power/rte_power_qos.h
new file mode 100644
index 0000000000..990c488373
--- /dev/null
+++ b/lib/power/rte_power_qos.h
@@ -0,0 +1,73 @@ 
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2024 HiSilicon Limited
+ */
+
+#ifndef RTE_POWER_QOS_H
+#define RTE_POWER_QOS_H
+
+#include <stdint.h>
+
+#include <rte_compat.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @file rte_power_qos.h
+ *
+ * PM QoS API.
+ *
+ * The CPU-wide resume latency limit has a positive impact on this CPU's idle
+ * state selection in each cpuidle governor.
+ * Please see the PM QoS on CPU wide in the following link:
+ * https://www.kernel.org/doc/html/latest/admin-guide/abi-testing.html?highlight=pm_qos_resume_latency_us#abi-sys-devices-power-pm-qos-resume-latency-us
+ *
+ * The deeper the idle state, the lower the power consumption, but the
+ * longer the resume time. Some service are delay sensitive and very except the
+ * low resume time, like interrupt packet receiving mode.
+ *
+ * In these case, per-CPU PM QoS API can be used to control this CPU's idle
+ * state selection and limit just enter the shallowest idle state to low the
+ * delay after sleep by setting strict resume latency (zero value).
+ */
+
+#define RTE_POWER_QOS_STRICT_LATENCY_VALUE             0
+#define RTE_POWER_QOS_RESUME_LATENCY_NO_CONSTRAINT    ((int)(UINT32_MAX >> 1))
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice.
+ *
+ * @param lcore_id
+ *   target logical core id
+ *
+ * @param latency
+ *   The latency should be greater than and equal to zero in microseconds unit.
+ *
+ * @return
+ *   0 on success. Otherwise negative value is returned.
+ */
+__rte_experimental
+int rte_power_qos_set_cpu_resume_latency(uint16_t lcore_id, int latency);
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice.
+ *
+ * Get the current resume latency of this logical core.
+ * The default value in kernel is @see RTE_POWER_QOS_RESUME_LATENCY_NO_CONSTRAINT
+ * if don't set it.
+ *
+ * @return
+ *   Negative value on failure.
+ *   >= 0 means the actual resume latency limit on this core.
+ */
+__rte_experimental
+int rte_power_qos_get_cpu_resume_latency(uint16_t lcore_id);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* RTE_POWER_QOS_H */
diff --git a/lib/power/version.map b/lib/power/version.map
index ad92a65f91..81b8ff11b7 100644
--- a/lib/power/version.map
+++ b/lib/power/version.map
@@ -51,4 +51,6 @@  EXPERIMENTAL {
 	rte_power_set_uncore_env;
 	rte_power_uncore_freqs;
 	rte_power_unset_uncore_env;
+	rte_power_qos_set_cpu_resume_latency;
+	rte_power_qos_get_cpu_resume_latency;
 };