projects / mirror_ubuntu-hirsute-kernel.git / blame
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1 | // SPDX-License-Identifier: GPL-2.0 |
| 2 | /* | |
| 3 | * haltpoll.c - haltpoll idle governor | |
| 4 | * | |
| 5 | * Copyright 2019 Red Hat, Inc. and/or its affiliates. | |
| 6 | * | |
| 7 | * This work is licensed under the terms of the GNU GPL, version 2. See | |
| 8 | * the COPYING file in the top-level directory. | |
| 9 | * | |
| 10 | * Authors: Marcelo Tosatti <mtosatti@redhat.com> | |
| 11 | */ | |
| 12 | ||
| 13 | #include <linux/kernel.h> | |
| 14 | #include <linux/cpuidle.h> | |
| 15 | #include <linux/time.h> | |
| 16 | #include <linux/ktime.h> | |
| 17 | #include <linux/hrtimer.h> | |
| 18 | #include <linux/tick.h> | |
| 19 | #include <linux/sched.h> | |
| 20 | #include <linux/module.h> | |
| 21 | #include <linux/kvm_para.h> | |
| 22 | ||
| 23 | static unsigned int guest_halt_poll_ns __read_mostly = 200000; | |
| 24 | module_param(guest_halt_poll_ns, uint, 0644); | |
| 25 | ||
| 26 | /* division factor to shrink halt_poll_ns */ | |
| 27 | static unsigned int guest_halt_poll_shrink __read_mostly = 2; | |
| 28 | module_param(guest_halt_poll_shrink, uint, 0644); | |
| 29 | ||
| 30 | /* multiplication factor to grow per-cpu poll_limit_ns */ | |
| 31 | static unsigned int guest_halt_poll_grow __read_mostly = 2; | |
| 32 | module_param(guest_halt_poll_grow, uint, 0644); | |
| 33 | ||
| 34 | /* value in us to start growing per-cpu halt_poll_ns */ | |
| 35 | static unsigned int guest_halt_poll_grow_start __read_mostly = 50000; | |
| 36 | module_param(guest_halt_poll_grow_start, uint, 0644); | |
| 37 | ||
| 38 | /* allow shrinking guest halt poll */ | |
| 39 | static bool guest_halt_poll_allow_shrink __read_mostly = true; | |
| 40 | module_param(guest_halt_poll_allow_shrink, bool, 0644); | |
| 41 | ||
| 42 | /** | |
| 43 | * haltpoll_select - selects the next idle state to enter | |
| 44 | * @drv: cpuidle driver containing state data | |
| 45 | * @dev: the CPU | |
| 46 | * @stop_tick: indication on whether or not to stop the tick | |
| 47 | */ | |
| 48 | static int haltpoll_select(struct cpuidle_driver *drv, | |
| 49 | struct cpuidle_device *dev, | |
| 50 | bool *stop_tick) | |
| 51 | { | |
| c1d51f68 | 52 | s64 latency_req = cpuidle_governor_latency_req(dev->cpu); |
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53 | |
| 54 | if (!drv->state_count || latency_req == 0) { | |
| 55 | *stop_tick = false; | |
| 56 | return 0; | |
| 57 | } | |
| 58 | ||
| 59 | if (dev->poll_limit_ns == 0) | |
| 60 | return 1; | |
| 61 | ||
| 62 | /* Last state was poll? */ | |
| 63 | if (dev->last_state_idx == 0) { | |
| 64 | /* Halt if no event occurred on poll window */ | |
| 65 | if (dev->poll_time_limit == true) | |
| 66 | return 1; | |
| 67 | ||
| 68 | *stop_tick = false; | |
| 69 | /* Otherwise, poll again */ | |
| 70 | return 0; | |
| 71 | } | |
| 72 | ||
| 73 | *stop_tick = false; | |
| 74 | /* Last state was halt: poll */ | |
| 75 | return 0; | |
| 76 | } | |
| 77 | ||
| c1d51f68 | 78 | static void adjust_poll_limit(struct cpuidle_device *dev, u64 block_ns) |
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79 | { |
| 80 | unsigned int val; | |
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81 | |
| 82 | /* Grow cpu_halt_poll_us if | |
| 83 | * cpu_halt_poll_us < block_ns < guest_halt_poll_us | |
| 84 | */ | |
| 85 | if (block_ns > dev->poll_limit_ns && block_ns <= guest_halt_poll_ns) { | |
| 86 | val = dev->poll_limit_ns * guest_halt_poll_grow; | |
| 87 | ||
| 88 | if (val < guest_halt_poll_grow_start) | |
| 89 | val = guest_halt_poll_grow_start; | |
| 90 | if (val > guest_halt_poll_ns) | |
| 91 | val = guest_halt_poll_ns; | |
| 92 | ||
| 93 | dev->poll_limit_ns = val; | |
| 94 | } else if (block_ns > guest_halt_poll_ns && | |
| 95 | guest_halt_poll_allow_shrink) { | |
| 96 | unsigned int shrink = guest_halt_poll_shrink; | |
| 97 | ||
| 98 | val = dev->poll_limit_ns; | |
| 99 | if (shrink == 0) | |
| 100 | val = 0; | |
| 101 | else | |
| 102 | val /= shrink; | |
| 103 | dev->poll_limit_ns = val; | |
| 104 | } | |
| 105 | } | |
| 106 | ||
| 107 | /** | |
| 108 | * haltpoll_reflect - update variables and update poll time | |
| 109 | * @dev: the CPU | |
| 110 | * @index: the index of actual entered state | |
| 111 | */ | |
| 112 | static void haltpoll_reflect(struct cpuidle_device *dev, int index) | |
| 113 | { | |
| 114 | dev->last_state_idx = index; | |
| 115 | ||
| 116 | if (index != 0) | |
| c1d51f68 | 117 | adjust_poll_limit(dev, dev->last_residency_ns); |
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118 | } |
| 119 | ||
| 120 | /** | |
| 121 | * haltpoll_enable_device - scans a CPU's states and does setup | |
| 122 | * @drv: cpuidle driver | |
| 123 | * @dev: the CPU | |
| 124 | */ | |
| 125 | static int haltpoll_enable_device(struct cpuidle_driver *drv, | |
| 126 | struct cpuidle_device *dev) | |
| 127 | { | |
| 128 | dev->poll_limit_ns = 0; | |
| 129 | ||
| 130 | return 0; | |
| 131 | } | |
| 132 | ||
| 133 | static struct cpuidle_governor haltpoll_governor = { | |
| 134 | .name = "haltpoll", | |
| 73214408 | 135 | .rating = 9, |
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136 | .enable = haltpoll_enable_device, |
| 137 | .select = haltpoll_select, | |
| 138 | .reflect = haltpoll_reflect, | |
| 139 | }; | |
| 140 | ||
| 141 | static int __init init_haltpoll(void) | |
| 142 | { | |
| 143 | if (kvm_para_available()) | |
| 144 | return cpuidle_register_governor(&haltpoll_governor); | |
| 145 | ||
| 146 | return 0; | |
| 147 | } | |
| 148 | ||
| 149 | postcore_initcall(init_haltpoll); |