[dpdk-dev] [PATCH v6 05/10] power: add PMD power management API and callback
Ananyev, Konstantin
konstantin.ananyev at intel.com
Wed Oct 14 20:41:07 CEST 2020
> From: Liang Ma <liang.j.ma at 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. Pause instruction
>
> Instead of move the core into deeper C state, this method uses the
> pause 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 at intel.com>
> Signed-off-by: Anatoly Burakov <anatoly.burakov at intel.com>
> ---
>
> Notes:
> v6:
> - Added wakeup mechanism for UMWAIT
> - Removed memory allocation (everything is now allocated statically)
> - Fixed various typos and comments
> - Check for invalid queue ID
> - Moved release notes to this patch
>
> v5:
> - Make error checking more robust
> - Prevent initializing scaling if ACPI or PSTATE env wasn't set
> - Prevent initializing UMWAIT path if PMD doesn't support get_wake_addr
> - Add some debug logging
> - Replace x86-specific code path to generic path using the intrinsic check
>
> doc/guides/rel_notes/release_20_11.rst | 11 +
> lib/librte_power/meson.build | 5 +-
> lib/librte_power/rte_power_pmd_mgmt.c | 300 +++++++++++++++++++++++++
> lib/librte_power/rte_power_pmd_mgmt.h | 92 ++++++++
> lib/librte_power/rte_power_version.map | 4 +
> 5 files changed, 410 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/rel_notes/release_20_11.rst b/doc/guides/rel_notes/release_20_11.rst
> index ca4f43f7f9..06b822aa36 100644
> --- a/doc/guides/rel_notes/release_20_11.rst
> +++ b/doc/guides/rel_notes/release_20_11.rst
> @@ -197,6 +197,17 @@ New Features
> * Added new ``RTE_ACL_CLASSIFY_AVX512X32`` vector implementation,
> which can process up to 32 flows in parallel. Requires AVX512 support.
>
> +* **Add PMD power management mechanism**
> +
> + 3 new Ethernet PMD power management mechanism is added through existing
> + RX callback infrastructure.
> +
> + * Add power saving scheme based on UMWAIT instruction (x86 only)
> + * Add power saving scheme based on ``rte_pause()``
> + * Add power saving scheme based on frequency scaling through the power library
> + * Add new EXPERIMENTAL API ``rte_power_pmd_mgmt_queue_enable()``
> + * Add new EXPERIMENTAL API ``rte_power_pmd_mgmt_queue_disable()``
> +
>
> Removed Items
> -------------
> diff --git a/lib/librte_power/meson.build b/lib/librte_power/meson.build
> index 78c031c943..cc3c7a8646 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..2b7d2a1a46
> --- /dev/null
> +++ b/lib/librte_power/rte_power_pmd_mgmt.c
> @@ -0,0 +1,300 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2010-2020 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
> +
> +/**
> + * 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 {
> + 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 */
> + rte_spinlock_t umwait_lock;
> + /**< Per-queue status lock - used only for UMWAIT mode */
> + volatile void *wait_addr;
> + /**< UMWAIT wakeup address */
> + 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];
> +
> +/* trigger a write to the cache line we're waiting on */
> +static void umwait_wakeup(volatile void *addr)
> +{
> + uint64_t val;
> +
> + val = __atomic_load_n((volatile uint64_t *)addr, __ATOMIC_RELAXED);
> + __atomic_compare_exchange_n((volatile uint64_t *)addr, &val, val, 0,
> + __ATOMIC_RELAXED, __ATOMIC_RELAXED);
> +}
> +
> +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)) {
> + volatile void *target_addr;
> + uint64_t expected, mask;
> + uint16_t ret;
> + uint8_t data_sz;
> +
> + /*
> + * get address of next descriptor in the RX
> + * ring for this queue, as well as expected
> + * value and a mask.
> + */
> + ret = rte_eth_get_wake_addr(port_id, qidx,
> + &target_addr, &expected, &mask,
> + &data_sz);
> + if (ret == 0) {
> + /*
> + * we need to ensure we can wake up by another
> + * thread triggering a write, so we need the
> + * address to always be up to date.
> + */
> + rte_spinlock_lock(&q_conf->umwait_lock);
I think you need to check state here, and _disable() have to set state with lock grabbed.
Otherwise this lock wouldn't protect you from race conditions.
As an example:
CP at T0:
rte_spinlock_lock(&queue_cfg->umwait_lock);
if (queue_cfg->wait_addr != NULL) //wait_addr == NULL, fallthrough
rte_spinlock_unlock(&queue_cfg->umwait_lock);
DP at T1:
rte_spinlock_lock(&queue_cfg->umwait_lock);
queue_cfg->wait_addr = target_addr;
monitor_sync(...); // DP was put to sleep
CP at T2:
queue_cfg->cur_cb = NULL;
queue_cfg->pwr_mgmt_state = PMD_MGMT_DISABLED;
ret = 0;
rte_power_pmd_mgmt_queue_disable() finished with success,
but DP core wasn't wokenup.
To be more specific:
clb_umwait(...) {
...
lock(&qcfg->lck);
if (qcfg->state == ENABLED) {
qcfg->wake_addr = addr;
monitor_sync(addr, ...,&qcfg->lck);
}
unlock(&qcfg->lck);
...
}
_disable(...) {
...
lock(&qcfg->lck);
qcfg->state = DISABLED;
if (qcfg->wake_addr != NULL)
monitor_wakeup(qcfg->wake_addr);
unlock(&qcfg->lock);
...
}
> + q_conf->wait_addr = target_addr;
> + /* -1ULL is maximum value for TSC */
> + rte_power_monitor_sync(target_addr, expected,
> + mask, -1ULL, data_sz,
> + &q_conf->umwait_lock);
> + /* erase the address */
> + q_conf->wait_addr = NULL;
> + rte_spinlock_unlock(&q_conf->umwait_lock);
> + }
> + }
> + } 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))
> + rte_delay_us(1);
> + } 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_pmd_mgmt_queue_enable(unsigned int lcore_id,
> + uint16_t port_id, uint16_t queue_id,
> + enum rte_power_pmd_mgmt_type mode)
> +{
> + struct rte_eth_dev *dev;
> + struct pmd_queue_cfg *queue_cfg;
> + int ret;
> +
> + RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -EINVAL);
> + dev = &rte_eth_devices[port_id];
> +
> + /* check if queue id is valid */
> + if (queue_id >= dev->data->nb_rx_queues ||
> + queue_id >= RTE_MAX_QUEUES_PER_PORT) {
> + return -EINVAL;
> + }
> +
> + queue_cfg = &port_cfg[port_id][queue_id];
> +
> + if (queue_cfg->pwr_mgmt_state == PMD_MGMT_ENABLED) {
> + ret = -EINVAL;
> + goto end;
> + }
> +
> + switch (mode) {
> + case RTE_POWER_MGMT_TYPE_WAIT:
> + {
> + /* check if rte_power_monitor is supported */
> + uint64_t dummy_expected, dummy_mask;
> + struct rte_cpu_intrinsics i;
> + volatile void *dummy_addr;
> + uint8_t dummy_sz;
> +
> + rte_cpu_get_intrinsics_support(&i);
> +
> + if (!i.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_wake_addr(port_id, queue_id,
> + &dummy_addr, &dummy_expected,
> + &dummy_mask, &dummy_sz) == -ENOTSUP) {
> + RTE_LOG(DEBUG, POWER, "The device does not support rte_eth_rxq_ring_addr_get\n");
> + ret = -ENOTSUP;
> + goto end;
> + }
> + /* initialize UMWAIT spinlock */
> + rte_spinlock_init(&queue_cfg->umwait_lock);
I think don't need to do that.
It supposed to be in valid state (otherwise you are probably in trouble anyway).
> +
> + /* 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;
> +
> + queue_cfg->cur_cb = rte_eth_add_rx_callback(port_id, queue_id,
> + clb_umwait, NULL);
Would be a bit cleaner/nicer to move add_rx_callback out of switch() {}
As you have to do it always anyway.
Same thought for disable() and remove_rx_callback().
> + 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;
> +
> + queue_cfg->cur_cb = rte_eth_add_rx_callback(port_id,
> + queue_id, clb_scale_freq, NULL);
> + break;
> + }
> + case RTE_POWER_MGMT_TYPE_PAUSE:
> + /* 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;
> +
> + 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_pmd_mgmt_queue_disable(unsigned int lcore_id,
> + uint16_t port_id, uint16_t queue_id)
> +{
> + struct pmd_queue_cfg *queue_cfg;
> + int ret;
> +
> + queue_cfg = &port_cfg[port_id][queue_id];
> +
> + if (queue_cfg->pwr_mgmt_state == PMD_MGMT_DISABLED) {
> + ret = -EINVAL;
> + goto end;
> + }
> +
> + switch (queue_cfg->cb_mode) {
> + case RTE_POWER_MGMT_TYPE_WAIT:
> + rte_spinlock_lock(&queue_cfg->umwait_lock);
> +
> + /* wake up the core from UMWAIT sleep, if any */
> + if (queue_cfg->wait_addr != NULL)
> + umwait_wakeup(queue_cfg->wait_addr);
> +
> + rte_spinlock_unlock(&queue_cfg->umwait_lock);
> + /* 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;
> + queue_cfg->pwr_mgmt_state = PMD_MGMT_DISABLED;
> + ret = 0;
> +end:
> + return ret;
> +}
> 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..a7a3f98268
> --- /dev/null
> +++ b/lib/librte_power/rte_power_pmd_mgmt.h
> @@ -0,0 +1,92 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2010-2020 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 {
> + /** WAIT callback mode. */
> + RTE_POWER_MGMT_TYPE_WAIT = 1,
> + /** PAUSE callback mode. */
> + RTE_POWER_MGMT_TYPE_PAUSE,
> + /** Freq Scaling callback mode. */
> + RTE_POWER_MGMT_TYPE_SCALE,
> +};
> +
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change, or be removed, without prior notice
> + *
> + * Setup per-queue power management callback.
> + *
> + * @note This function is not thread-safe.
> + *
> + * @param lcore_id
> + * lcore_id.
> + * @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 callback function type.
> +
> + * @return
> + * 0 on success
> + * <0 on error
> + */
> +__rte_experimental
> +int
> +rte_power_pmd_mgmt_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
> + *
> + * Remove per-queue power management callback.
> + *
> + * @note This function is not thread-safe.
> + *
> + * @param lcore_id
> + * lcore_id.
> + * @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_pmd_mgmt_queue_disable(unsigned int lcore_id,
> + uint16_t port_id,
> + uint16_t queue_id);
> +#ifdef __cplusplus
> +}
> +#endif
> +
> +#endif
> diff --git a/lib/librte_power/rte_power_version.map b/lib/librte_power/rte_power_version.map
> index 69ca9af616..3f2f6cd6f6 100644
> --- a/lib/librte_power/rte_power_version.map
> +++ b/lib/librte_power/rte_power_version.map
> @@ -34,4 +34,8 @@ EXPERIMENTAL {
> rte_power_guest_channel_receive_msg;
> rte_power_poll_stat_fetch;
> rte_power_poll_stat_update;
> + # added in 20.11
> + rte_power_pmd_mgmt_queue_enable;
> + rte_power_pmd_mgmt_queue_disable;
> +
> };
> --
> 2.17.1
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