[dpdk-dev] [PATCH v18 1/2] power: add PMD power management API and callback

[Anatoly Burakov <anatoly.burakov@intel.com>]

From: Liang Ma <liang.j.ma@intel.com>

Add a simple on/off switch that will enable saving power when no
packets are arriving. It is based on counting the number of empty
polls and, when the number reaches a certain threshold, entering an
architecture-defined optimized power state that will either wait
until a TSC timestamp expires, or when packets arrive.

This API mandates a core-to-single-queue mapping (that is, multiple
queued per device are supported, but they have to be polled on different
cores).

This design is using PMD RX callbacks.

1. UMWAIT/UMONITOR:

   When a certain threshold of empty polls is reached, the core will go
   into a power optimized sleep while waiting on an address of next RX
   descriptor to be written to.

2. TPAUSE/Pause instruction

   This method uses the pause (or TPAUSE, if available) instruction to
   avoid busy polling.

3. Frequency scaling
   Reuse existing DPDK power library to scale up/down core frequency
   depending on traffic volume.

Signed-off-by: Liang Ma <liang.j.ma@intel.com>
Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Acked-by: David Hunt <david.hunt@intel.com>
---

Notes:
    v17:
    - Added memory barriers suggested by Konstantin
    - Removed the BUSY state

 doc/guides/prog_guide/power_man.rst    |  41 +++
 doc/guides/rel_notes/release_21_02.rst |  10 +
 lib/librte_power/meson.build           |   5 +-
 lib/librte_power/rte_power_pmd_mgmt.c  | 365 +++++++++++++++++++++++++
 lib/librte_power/rte_power_pmd_mgmt.h  |  91 ++++++
 lib/librte_power/version.map           |   5 +
 6 files changed, 515 insertions(+), 2 deletions(-)
 create mode 100644 lib/librte_power/rte_power_pmd_mgmt.c
 create mode 100644 lib/librte_power/rte_power_pmd_mgmt.h

diff --git a/doc/guides/prog_guide/power_man.rst b/doc/guides/prog_guide/power_man.rst
index 0a3755a901..f36ba0027c 100644
--- a/doc/guides/prog_guide/power_man.rst
+++ b/doc/guides/prog_guide/power_man.rst
@@ -192,6 +192,47 @@ User Cases
 ----------
 The mechanism can applied to any device which is based on polling. e.g. NIC, FPGA.
 
+Ethernet PMD Power Management API
+---------------------------------
+
+Abstract
+~~~~~~~~
+Existing power management mechanisms require developers to change application
+design or change code to make use of it. The PMD power management API provides a
+convenient alternative by utilizing Ethernet PMD RX callbacks, and triggering
+power saving whenever empty poll count reaches a certain number.
+
+  * Monitor
+
+   This power saving scheme will put the CPU into optimized power state and use
+   the ``rte_power_monitor()`` function to monitor the Ethernet PMD RX
+   descriptor address, and wake the CPU up whenever there's new traffic.
+
+  * Pause
+
+   This power saving scheme will avoid busy polling by either entering
+   power-optimized sleep state with ``rte_power_pause()`` function, or, if it's
+   not available, use ``rte_pause()``.
+
+  * Frequency scaling
+
+   This power saving scheme will use existing ``librte_power`` library
+   functionality to scale the core frequency up/down depending on traffic
+   volume.
+
+
+.. note::
+
+   Currently, this power management API is limited to mandatory mapping of 1
+   queue to 1 core (multiple queues are supported, but they must be polled from
+   different cores).
+
+API Overview for Ethernet PMD Power Management
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+* **Queue Enable**: Enable specific power scheme for certain queue/port/core.
+
+* **Queue Disable**: Disable power scheme for certain queue/port/core.
+
 References
 ----------
 
diff --git a/doc/guides/rel_notes/release_21_02.rst b/doc/guides/rel_notes/release_21_02.rst
index be5ea4370c..1988960b76 100644
--- a/doc/guides/rel_notes/release_21_02.rst
+++ b/doc/guides/rel_notes/release_21_02.rst
@@ -76,6 +76,16 @@ New Features
 
   * Added inner UDP/IPv4 support for VXLAN IPv4 GSO.
 
+* **Added Ethernet PMD power management helper API.**
+
+  A new helper API has been added to make using Ethernet PMD power management
+  easier for the user: ``rte_power_ethdev_pmgmt_queue_enable()``. Three power
+  management schemes are supported initially:
+
+  * Power saving based on UMWAIT instruction (x86 only)
+  * Power saving based on ``rte_pause()`` (generic) or TPAUSE instruction (x86 only)
+  * Power saving based on frequency scaling through the ``librte_power`` library
+
 
 Removed Items
 -------------
diff --git a/lib/librte_power/meson.build b/lib/librte_power/meson.build
index 4b4cf1b90b..e5a11cb834 100644
--- a/lib/librte_power/meson.build
+++ b/lib/librte_power/meson.build
@@ -9,6 +9,7 @@ sources = files('rte_power.c', 'power_acpi_cpufreq.c',
 		'power_kvm_vm.c', 'guest_channel.c',
 		'rte_power_empty_poll.c',
 		'power_pstate_cpufreq.c',
+		'rte_power_pmd_mgmt.c',
 		'power_common.c')
-headers = files('rte_power.h','rte_power_empty_poll.h')
-deps += ['timer']
+headers = files('rte_power.h','rte_power_empty_poll.h','rte_power_pmd_mgmt.h')
+deps += ['timer', 'ethdev']
diff --git a/lib/librte_power/rte_power_pmd_mgmt.c b/lib/librte_power/rte_power_pmd_mgmt.c
new file mode 100644
index 0000000000..454ef7091e
--- /dev/null
+++ b/lib/librte_power/rte_power_pmd_mgmt.c
@@ -0,0 +1,365 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2020 Intel Corporation
+ */
+
+#include <rte_lcore.h>
+#include <rte_cycles.h>
+#include <rte_cpuflags.h>
+#include <rte_malloc.h>
+#include <rte_ethdev.h>
+#include <rte_power_intrinsics.h>
+
+#include "rte_power_pmd_mgmt.h"
+
+#define EMPTYPOLL_MAX  512
+
+/* store some internal state */
+static struct pmd_conf_data {
+	/** what do we support? */
+	struct rte_cpu_intrinsics intrinsics_support;
+	/** pre-calculated tsc diff for 1us */
+	uint64_t tsc_per_us;
+	/** how many rte_pause can we fit in a microsecond? */
+	uint64_t pause_per_us;
+} global_data;
+
+/**
+ * Possible power management states of an ethdev port.
+ */
+enum pmd_mgmt_state {
+	/** Device power management is disabled. */
+	PMD_MGMT_DISABLED = 0,
+	/** Device power management is enabled. */
+	PMD_MGMT_ENABLED
+};
+
+struct pmd_queue_cfg {
+	volatile enum pmd_mgmt_state pwr_mgmt_state;
+	/**< State of power management for this queue */
+	enum rte_power_pmd_mgmt_type cb_mode;
+	/**< Callback mode for this queue */
+	const struct rte_eth_rxtx_callback *cur_cb;
+	/**< Callback instance */
+	volatile bool umwait_in_progress;
+	/**< are we currently sleeping? */
+	uint64_t empty_poll_stats;
+	/**< Number of empty polls */
+} __rte_cache_aligned;
+
+static struct pmd_queue_cfg port_cfg[RTE_MAX_ETHPORTS][RTE_MAX_QUEUES_PER_PORT];
+
+static void
+calc_tsc(void)
+{
+	const uint64_t hz = rte_get_timer_hz();
+	const uint64_t tsc_per_us = hz / US_PER_S; /* 1us */
+
+	global_data.tsc_per_us = tsc_per_us;
+
+	/* only do this if we don't have tpause */
+	if (!global_data.intrinsics_support.power_pause) {
+		const uint64_t start = rte_rdtsc_precise();
+		const uint32_t n_pauses = 10000;
+		double us, us_per_pause;
+		uint64_t end;
+		unsigned int i;
+
+		/* estimate number of rte_pause() calls per us*/
+		for (i = 0; i < n_pauses; i++)
+			rte_pause();
+
+		end = rte_rdtsc_precise();
+		us = (end - start) / (double)tsc_per_us;
+		us_per_pause = us / n_pauses;
+
+		global_data.pause_per_us = (uint64_t)(1.0 / us_per_pause);
+	}
+}
+
+static uint16_t
+clb_umwait(uint16_t port_id, uint16_t qidx, struct rte_mbuf **pkts __rte_unused,
+		uint16_t nb_rx, uint16_t max_pkts __rte_unused,
+		void *addr __rte_unused)
+{
+
+	struct pmd_queue_cfg *q_conf;
+
+	q_conf = &port_cfg[port_id][qidx];
+
+	if (unlikely(nb_rx == 0)) {
+		q_conf->empty_poll_stats++;
+		if (unlikely(q_conf->empty_poll_stats > EMPTYPOLL_MAX)) {
+			struct rte_power_monitor_cond pmc;
+			uint16_t ret;
+
+			/*
+			 * we might get a cancellation request while being
+			 * inside the callback, in which case the wakeup
+			 * wouldn't work because it would've arrived too early.
+			 *
+			 * to get around this, we notify the other thread that
+			 * we're sleeping, so that it can spin until we're done.
+			 * unsolicited wakeups are perfectly safe.
+			 */
+			q_conf->umwait_in_progress = true;
+
+			rte_atomic_thread_fence(__ATOMIC_SEQ_CST);
+
+			/* check if we need to cancel sleep */
+			if (q_conf->pwr_mgmt_state == PMD_MGMT_ENABLED) {
+				/* use monitoring condition to sleep */
+				ret = rte_eth_get_monitor_addr(port_id, qidx,
+						&pmc);
+				if (ret == 0)
+					rte_power_monitor(&pmc, -1ULL);
+			}
+			q_conf->umwait_in_progress = false;
+
+			rte_atomic_thread_fence(__ATOMIC_SEQ_CST);
+		}
+	} else
+		q_conf->empty_poll_stats = 0;
+
+	return nb_rx;
+}
+
+static uint16_t
+clb_pause(uint16_t port_id, uint16_t qidx, struct rte_mbuf **pkts __rte_unused,
+		uint16_t nb_rx, uint16_t max_pkts __rte_unused,
+		void *addr __rte_unused)
+{
+	struct pmd_queue_cfg *q_conf;
+
+	q_conf = &port_cfg[port_id][qidx];
+
+	if (unlikely(nb_rx == 0)) {
+		q_conf->empty_poll_stats++;
+		/* sleep for 1 microsecond */
+		if (unlikely(q_conf->empty_poll_stats > EMPTYPOLL_MAX)) {
+			/* use tpause if we have it */
+			if (global_data.intrinsics_support.power_pause) {
+				const uint64_t cur = rte_rdtsc();
+				const uint64_t wait_tsc =
+						cur + global_data.tsc_per_us;
+				rte_power_pause(wait_tsc);
+			} else {
+				uint64_t i;
+				for (i = 0; i < global_data.pause_per_us; i++)
+					rte_pause();
+			}
+		}
+	} else
+		q_conf->empty_poll_stats = 0;
+
+	return nb_rx;
+}
+
+static uint16_t
+clb_scale_freq(uint16_t port_id, uint16_t qidx,
+		struct rte_mbuf **pkts __rte_unused, uint16_t nb_rx,
+		uint16_t max_pkts __rte_unused, void *_  __rte_unused)
+{
+	struct pmd_queue_cfg *q_conf;
+
+	q_conf = &port_cfg[port_id][qidx];
+
+	if (unlikely(nb_rx == 0)) {
+		q_conf->empty_poll_stats++;
+		if (unlikely(q_conf->empty_poll_stats > EMPTYPOLL_MAX))
+			/* scale down freq */
+			rte_power_freq_min(rte_lcore_id());
+	} else {
+		q_conf->empty_poll_stats = 0;
+		/* scale up freq */
+		rte_power_freq_max(rte_lcore_id());
+	}
+
+	return nb_rx;
+}
+
+int
+rte_power_ethdev_pmgmt_queue_enable(unsigned int lcore_id, uint16_t port_id,
+		uint16_t queue_id, enum rte_power_pmd_mgmt_type mode)
+{
+	struct pmd_queue_cfg *queue_cfg;
+	struct rte_eth_dev_info info;
+	int ret;
+
+	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -EINVAL);
+
+	if (queue_id >= RTE_MAX_QUEUES_PER_PORT || lcore_id >= RTE_MAX_LCORE) {
+		ret = -EINVAL;
+		goto end;
+	}
+
+	if (rte_eth_dev_info_get(port_id, &info) < 0) {
+		ret = -EINVAL;
+		goto end;
+	}
+
+	/* check if queue id is valid */
+	if (queue_id >= info.nb_rx_queues) {
+		ret = -EINVAL;
+		goto end;
+	}
+
+	queue_cfg = &port_cfg[port_id][queue_id];
+
+	if (queue_cfg->pwr_mgmt_state != PMD_MGMT_DISABLED) {
+		ret = -EINVAL;
+		goto end;
+	}
+
+	/* we need this in various places */
+	rte_cpu_get_intrinsics_support(&global_data.intrinsics_support);
+
+	switch (mode) {
+	case RTE_POWER_MGMT_TYPE_MONITOR:
+	{
+		struct rte_power_monitor_cond dummy;
+
+		/* check if rte_power_monitor is supported */
+		if (!global_data.intrinsics_support.power_monitor) {
+			RTE_LOG(DEBUG, POWER, "Monitoring intrinsics are not supported\n");
+			ret = -ENOTSUP;
+			goto end;
+		}
+
+		/* check if the device supports the necessary PMD API */
+		if (rte_eth_get_monitor_addr(port_id, queue_id,
+				&dummy) == -ENOTSUP) {
+			RTE_LOG(DEBUG, POWER, "The device does not support rte_eth_get_monitor_addr\n");
+			ret = -ENOTSUP;
+			goto end;
+		}
+		/* initialize data before enabling the callback */
+		queue_cfg->empty_poll_stats = 0;
+		queue_cfg->cb_mode = mode;
+		queue_cfg->umwait_in_progress = false;
+		queue_cfg->pwr_mgmt_state = PMD_MGMT_ENABLED;
+
+		/* ensure we update our state before callback starts */
+		rte_atomic_thread_fence(__ATOMIC_SEQ_CST);
+
+		queue_cfg->cur_cb = rte_eth_add_rx_callback(port_id, queue_id,
+				clb_umwait, NULL);
+		break;
+	}
+	case RTE_POWER_MGMT_TYPE_SCALE:
+	{
+		enum power_management_env env;
+		/* only PSTATE and ACPI modes are supported */
+		if (!rte_power_check_env_supported(PM_ENV_ACPI_CPUFREQ) &&
+				!rte_power_check_env_supported(
+					PM_ENV_PSTATE_CPUFREQ)) {
+			RTE_LOG(DEBUG, POWER, "Neither ACPI nor PSTATE modes are supported\n");
+			ret = -ENOTSUP;
+			goto end;
+		}
+		/* ensure we could initialize the power library */
+		if (rte_power_init(lcore_id)) {
+			ret = -EINVAL;
+			goto end;
+		}
+		/* ensure we initialized the correct env */
+		env = rte_power_get_env();
+		if (env != PM_ENV_ACPI_CPUFREQ &&
+				env != PM_ENV_PSTATE_CPUFREQ) {
+			RTE_LOG(DEBUG, POWER, "Neither ACPI nor PSTATE modes were initialized\n");
+			ret = -ENOTSUP;
+			goto end;
+		}
+		/* initialize data before enabling the callback */
+		queue_cfg->empty_poll_stats = 0;
+		queue_cfg->cb_mode = mode;
+		queue_cfg->pwr_mgmt_state = PMD_MGMT_ENABLED;
+
+		/* this is not necessary here, but do it anyway */
+		rte_atomic_thread_fence(__ATOMIC_SEQ_CST);
+
+		queue_cfg->cur_cb = rte_eth_add_rx_callback(port_id,
+				queue_id, clb_scale_freq, NULL);
+		break;
+	}
+	case RTE_POWER_MGMT_TYPE_PAUSE:
+		/* figure out various time-to-tsc conversions */
+		if (global_data.tsc_per_us == 0)
+			calc_tsc();
+
+		/* initialize data before enabling the callback */
+		queue_cfg->empty_poll_stats = 0;
+		queue_cfg->cb_mode = mode;
+		queue_cfg->pwr_mgmt_state = PMD_MGMT_ENABLED;
+
+		/* this is not necessary here, but do it anyway */
+		rte_atomic_thread_fence(__ATOMIC_SEQ_CST);
+
+		queue_cfg->cur_cb = rte_eth_add_rx_callback(port_id, queue_id,
+				clb_pause, NULL);
+		break;
+	}
+	ret = 0;
+end:
+	return ret;
+}
+
+int
+rte_power_ethdev_pmgmt_queue_disable(unsigned int lcore_id,
+		uint16_t port_id, uint16_t queue_id)
+{
+	struct pmd_queue_cfg *queue_cfg;
+
+	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -EINVAL);
+
+	if (lcore_id >= RTE_MAX_LCORE || queue_id >= RTE_MAX_QUEUES_PER_PORT)
+		return -EINVAL;
+
+	/* no need to check queue id as wrong queue id would not be enabled */
+	queue_cfg = &port_cfg[port_id][queue_id];
+
+	if (queue_cfg->pwr_mgmt_state != PMD_MGMT_ENABLED)
+		return -EINVAL;
+
+	/* stop any callbacks from progressing */
+	queue_cfg->pwr_mgmt_state = PMD_MGMT_DISABLED;
+
+	/* ensure we update our state before continuing */
+	rte_atomic_thread_fence(__ATOMIC_SEQ_CST);
+
+	switch (queue_cfg->cb_mode) {
+	case RTE_POWER_MGMT_TYPE_MONITOR:
+	{
+		bool exit = false;
+		do {
+			/*
+			 * we may request cancellation while the other thread
+			 * has just entered the callback but hasn't started
+			 * sleeping yet, so keep waking it up until we know it's
+			 * done sleeping.
+			 */
+			if (queue_cfg->umwait_in_progress)
+				rte_power_monitor_wakeup(lcore_id);
+			else
+				exit = true;
+		} while (!exit);
+	}
+	/* fall-through */
+	case RTE_POWER_MGMT_TYPE_PAUSE:
+		rte_eth_remove_rx_callback(port_id, queue_id,
+				queue_cfg->cur_cb);
+		break;
+	case RTE_POWER_MGMT_TYPE_SCALE:
+		rte_power_freq_max(lcore_id);
+		rte_eth_remove_rx_callback(port_id, queue_id,
+				queue_cfg->cur_cb);
+		rte_power_exit(lcore_id);
+		break;
+	}
+	/*
+	 * we don't free the RX callback here because it is unsafe to do so
+	 * unless we know for a fact that all data plane threads have stopped.
+	 */
+	queue_cfg->cur_cb = NULL;
+
+	return 0;
+}
diff --git a/lib/librte_power/rte_power_pmd_mgmt.h b/lib/librte_power/rte_power_pmd_mgmt.h
new file mode 100644
index 0000000000..7a0ac24625
--- /dev/null
+++ b/lib/librte_power/rte_power_pmd_mgmt.h
@@ -0,0 +1,91 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2020 Intel Corporation
+ */
+
+#ifndef _RTE_POWER_PMD_MGMT_H
+#define _RTE_POWER_PMD_MGMT_H
+
+/**
+ * @file
+ * RTE PMD Power Management
+ */
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#include <rte_common.h>
+#include <rte_byteorder.h>
+#include <rte_log.h>
+#include <rte_power.h>
+#include <rte_atomic.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * PMD Power Management Type
+ */
+enum rte_power_pmd_mgmt_type {
+	/** Use power-optimized monitoring to wait for incoming traffic */
+	RTE_POWER_MGMT_TYPE_MONITOR = 1,
+	/** Use power-optimized sleep to avoid busy polling */
+	RTE_POWER_MGMT_TYPE_PAUSE,
+	/** Use frequency scaling when traffic is low */
+	RTE_POWER_MGMT_TYPE_SCALE,
+};
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change, or be removed, without prior notice.
+ *
+ * Enable power management on a specified Ethernet device Rx queue and lcore.
+ *
+ * @note This function is not thread-safe.
+ *
+ * @param lcore_id
+ *   The lcore the Rx queue will be polled from.
+ * @param port_id
+ *   The port identifier of the Ethernet device.
+ * @param queue_id
+ *   The queue identifier of the Ethernet device.
+ * @param mode
+ *   The power management scheme to use for specified Rx queue.
+ * @return
+ *   0 on success
+ *   <0 on error
+ */
+__rte_experimental
+int
+rte_power_ethdev_pmgmt_queue_enable(unsigned int lcore_id,
+		uint16_t port_id, uint16_t queue_id,
+		enum rte_power_pmd_mgmt_type mode);
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change, or be removed, without prior notice.
+ *
+ * Disable power management on a specified Ethernet device Rx queue and lcore.
+ *
+ * @note This function is not thread-safe.
+ *
+ * @param lcore_id
+ *   The lcore the Rx queue is polled from.
+ * @param port_id
+ *   The port identifier of the Ethernet device.
+ * @param queue_id
+ *   The queue identifier of the Ethernet device.
+ * @return
+ *   0 on success
+ *   <0 on error
+ */
+__rte_experimental
+int
+rte_power_ethdev_pmgmt_queue_disable(unsigned int lcore_id,
+		uint16_t port_id, uint16_t queue_id);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/lib/librte_power/version.map b/lib/librte_power/version.map
index 69ca9af616..f38a380212 100644
--- a/lib/librte_power/version.map
+++ b/lib/librte_power/version.map
@@ -34,4 +34,9 @@ EXPERIMENTAL {
 	rte_power_guest_channel_receive_msg;
 	rte_power_poll_stat_fetch;
 	rte_power_poll_stat_update;
+
+	# added in 21.02
+	rte_power_ethdev_pmgmt_queue_disable;
+	rte_power_ethdev_pmgmt_queue_enable;
+
 };
-- 
2.25.1