diff options
Diffstat (limited to 'drivers/cpuidle/governors/haltpoll.c')
| -rw-r--r-- | drivers/cpuidle/governors/haltpoll.c | 150 |
1 files changed, 150 insertions, 0 deletions
diff --git a/drivers/cpuidle/governors/haltpoll.c b/drivers/cpuidle/governors/haltpoll.c new file mode 100644 index 000000000000..7a703d2e0064 --- /dev/null +++ b/drivers/cpuidle/governors/haltpoll.c @@ -0,0 +1,150 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * haltpoll.c - haltpoll idle governor + * + * Copyright 2019 Red Hat, Inc. and/or its affiliates. + * + * This work is licensed under the terms of the GNU GPL, version 2. See + * the COPYING file in the top-level directory. + * + * Authors: Marcelo Tosatti <mtosatti@redhat.com> + */ + +#include <linux/kernel.h> +#include <linux/cpuidle.h> +#include <linux/time.h> +#include <linux/ktime.h> +#include <linux/hrtimer.h> +#include <linux/tick.h> +#include <linux/sched.h> +#include <linux/module.h> +#include <linux/kvm_para.h> + +static unsigned int guest_halt_poll_ns __read_mostly = 200000; +module_param(guest_halt_poll_ns, uint, 0644); + +/* division factor to shrink halt_poll_ns */ +static unsigned int guest_halt_poll_shrink __read_mostly = 2; +module_param(guest_halt_poll_shrink, uint, 0644); + +/* multiplication factor to grow per-cpu poll_limit_ns */ +static unsigned int guest_halt_poll_grow __read_mostly = 2; +module_param(guest_halt_poll_grow, uint, 0644); + +/* value in us to start growing per-cpu halt_poll_ns */ +static unsigned int guest_halt_poll_grow_start __read_mostly = 50000; +module_param(guest_halt_poll_grow_start, uint, 0644); + +/* allow shrinking guest halt poll */ +static bool guest_halt_poll_allow_shrink __read_mostly = true; +module_param(guest_halt_poll_allow_shrink, bool, 0644); + +/** + * haltpoll_select - selects the next idle state to enter + * @drv: cpuidle driver containing state data + * @dev: the CPU + * @stop_tick: indication on whether or not to stop the tick + */ +static int haltpoll_select(struct cpuidle_driver *drv, + struct cpuidle_device *dev, + bool *stop_tick) +{ + int latency_req = cpuidle_governor_latency_req(dev->cpu); + + if (!drv->state_count || latency_req == 0) { + *stop_tick = false; + return 0; + } + + if (dev->poll_limit_ns == 0) + return 1; + + /* Last state was poll? */ + if (dev->last_state_idx == 0) { + /* Halt if no event occurred on poll window */ + if (dev->poll_time_limit == true) + return 1; + + *stop_tick = false; + /* Otherwise, poll again */ + return 0; + } + + *stop_tick = false; + /* Last state was halt: poll */ + return 0; +} + +static void adjust_poll_limit(struct cpuidle_device *dev, unsigned int block_us) +{ + unsigned int val; + u64 block_ns = block_us*NSEC_PER_USEC; + + /* Grow cpu_halt_poll_us if + * cpu_halt_poll_us < block_ns < guest_halt_poll_us + */ + if (block_ns > dev->poll_limit_ns && block_ns <= guest_halt_poll_ns) { + val = dev->poll_limit_ns * guest_halt_poll_grow; + + if (val < guest_halt_poll_grow_start) + val = guest_halt_poll_grow_start; + if (val > guest_halt_poll_ns) + val = guest_halt_poll_ns; + + dev->poll_limit_ns = val; + } else if (block_ns > guest_halt_poll_ns && + guest_halt_poll_allow_shrink) { + unsigned int shrink = guest_halt_poll_shrink; + + val = dev->poll_limit_ns; + if (shrink == 0) + val = 0; + else + val /= shrink; + dev->poll_limit_ns = val; + } +} + +/** + * haltpoll_reflect - update variables and update poll time + * @dev: the CPU + * @index: the index of actual entered state + */ +static void haltpoll_reflect(struct cpuidle_device *dev, int index) +{ + dev->last_state_idx = index; + + if (index != 0) + adjust_poll_limit(dev, dev->last_residency); +} + +/** + * haltpoll_enable_device - scans a CPU's states and does setup + * @drv: cpuidle driver + * @dev: the CPU + */ +static int haltpoll_enable_device(struct cpuidle_driver *drv, + struct cpuidle_device *dev) +{ + dev->poll_limit_ns = 0; + + return 0; +} + +static struct cpuidle_governor haltpoll_governor = { + .name = "haltpoll", + .rating = 9, + .enable = haltpoll_enable_device, + .select = haltpoll_select, + .reflect = haltpoll_reflect, +}; + +static int __init init_haltpoll(void) +{ + if (kvm_para_available()) + return cpuidle_register_governor(&haltpoll_governor); + + return 0; +} + +postcore_initcall(init_haltpoll); |