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 #include <trace/events/power.h>
23
24 static unsigned int guest_halt_poll_ns __read_mostly = 200000;
25 module_param(guest_halt_poll_ns, uint, 0644);
26
27 /* division factor to shrink halt_poll_ns */
28 static unsigned int guest_halt_poll_shrink __read_mostly = 2;
29 module_param(guest_halt_poll_shrink, uint, 0644);
30
31 /* multiplication factor to grow per-cpu poll_limit_ns */
32 static unsigned int guest_halt_poll_grow __read_mostly = 2;
33 module_param(guest_halt_poll_grow, uint, 0644);
34
35 /* value in us to start growing per-cpu halt_poll_ns */
36 static unsigned int guest_halt_poll_grow_start __read_mostly = 50000;
37 module_param(guest_halt_poll_grow_start, uint, 0644);
38
39 /* allow shrinking guest halt poll */
40 static bool guest_halt_poll_allow_shrink __read_mostly = true;
41 module_param(guest_halt_poll_allow_shrink, bool, 0644);
42
43 /**
44 * haltpoll_select - selects the next idle state to enter
45 * @drv: cpuidle driver containing state data
46 * @dev: the CPU
47 * @stop_tick: indication on whether or not to stop the tick
48 */
haltpoll_select(struct cpuidle_driver * drv,struct cpuidle_device * dev,bool * stop_tick)49 static int haltpoll_select(struct cpuidle_driver *drv,
50 struct cpuidle_device *dev,
51 bool *stop_tick)
52 {
53 s64 latency_req = cpuidle_governor_latency_req(dev->cpu);
54
55 if (!drv->state_count || latency_req == 0) {
56 *stop_tick = false;
57 return 0;
58 }
59
60 if (dev->poll_limit_ns == 0)
61 return 1;
62
63 /* Last state was poll? */
64 if (dev->last_state_idx == 0) {
65 /* Halt if no event occurred on poll window */
66 if (dev->poll_time_limit == true)
67 return 1;
68
69 *stop_tick = false;
70 /* Otherwise, poll again */
71 return 0;
72 }
73
74 *stop_tick = false;
75 /* Last state was halt: poll */
76 return 0;
77 }
78
adjust_poll_limit(struct cpuidle_device * dev,u64 block_ns)79 static void adjust_poll_limit(struct cpuidle_device *dev, u64 block_ns)
80 {
81 unsigned int val;
82
83 /* Grow cpu_halt_poll_us if
84 * cpu_halt_poll_us < block_ns < guest_halt_poll_us
85 */
86 if (block_ns > dev->poll_limit_ns && block_ns <= guest_halt_poll_ns) {
87 val = dev->poll_limit_ns * guest_halt_poll_grow;
88
89 if (val < guest_halt_poll_grow_start)
90 val = guest_halt_poll_grow_start;
91 if (val > guest_halt_poll_ns)
92 val = guest_halt_poll_ns;
93
94 trace_guest_halt_poll_ns_grow(val, dev->poll_limit_ns);
95 dev->poll_limit_ns = val;
96 } else if (block_ns > guest_halt_poll_ns &&
97 guest_halt_poll_allow_shrink) {
98 unsigned int shrink = guest_halt_poll_shrink;
99
100 val = dev->poll_limit_ns;
101 if (shrink == 0)
102 val = 0;
103 else
104 val /= shrink;
105 trace_guest_halt_poll_ns_shrink(val, dev->poll_limit_ns);
106 dev->poll_limit_ns = val;
107 }
108 }
109
110 /**
111 * haltpoll_reflect - update variables and update poll time
112 * @dev: the CPU
113 * @index: the index of actual entered state
114 */
haltpoll_reflect(struct cpuidle_device * dev,int index)115 static void haltpoll_reflect(struct cpuidle_device *dev, int index)
116 {
117 dev->last_state_idx = index;
118
119 if (index != 0)
120 adjust_poll_limit(dev, dev->last_residency_ns);
121 }
122
123 /**
124 * haltpoll_enable_device - scans a CPU's states and does setup
125 * @drv: cpuidle driver
126 * @dev: the CPU
127 */
haltpoll_enable_device(struct cpuidle_driver * drv,struct cpuidle_device * dev)128 static int haltpoll_enable_device(struct cpuidle_driver *drv,
129 struct cpuidle_device *dev)
130 {
131 dev->poll_limit_ns = 0;
132
133 return 0;
134 }
135
136 static struct cpuidle_governor haltpoll_governor = {
137 .name = "haltpoll",
138 .rating = 9,
139 .enable = haltpoll_enable_device,
140 .select = haltpoll_select,
141 .reflect = haltpoll_reflect,
142 };
143
init_haltpoll(void)144 static int __init init_haltpoll(void)
145 {
146 if (kvm_para_available())
147 return cpuidle_register_governor(&haltpoll_governor);
148
149 return 0;
150 }
151
152 postcore_initcall(init_haltpoll);
153