Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 1 | /* |
| 2 | * kernel/sched_cpupri.c |
| 3 | * |
| 4 | * CPU priority management |
| 5 | * |
| 6 | * Copyright (C) 2007-2008 Novell |
| 7 | * |
| 8 | * Author: Gregory Haskins <ghaskins@novell.com> |
| 9 | * |
| 10 | * This code tracks the priority of each CPU so that global migration |
| 11 | * decisions are easy to calculate. Each CPU can be in a state as follows: |
| 12 | * |
| 13 | * (INVALID), IDLE, NORMAL, RT1, ... RT99 |
| 14 | * |
| 15 | * going from the lowest priority to the highest. CPUs in the INVALID state |
| 16 | * are not eligible for routing. The system maintains this state with |
| 17 | * a 2 dimensional bitmap (the first for priority class, the second for cpus |
| 18 | * in that class). Therefore a typical application without affinity |
| 19 | * restrictions can find a suitable CPU with O(1) complexity (e.g. two bit |
| 20 | * searches). For tasks with affinity restrictions, the algorithm has a |
| 21 | * worst case complexity of O(min(102, nr_domcpus)), though the scenario that |
| 22 | * yields the worst case search is fairly contrived. |
| 23 | * |
| 24 | * This program is free software; you can redistribute it and/or |
| 25 | * modify it under the terms of the GNU General Public License |
| 26 | * as published by the Free Software Foundation; version 2 |
| 27 | * of the License. |
| 28 | */ |
| 29 | |
| 30 | #include "sched_cpupri.h" |
| 31 | |
| 32 | /* Convert between a 140 based task->prio, and our 102 based cpupri */ |
| 33 | static int convert_prio(int prio) |
| 34 | { |
| 35 | int cpupri; |
| 36 | |
| 37 | if (prio == CPUPRI_INVALID) |
| 38 | cpupri = CPUPRI_INVALID; |
| 39 | else if (prio == MAX_PRIO) |
| 40 | cpupri = CPUPRI_IDLE; |
| 41 | else if (prio >= MAX_RT_PRIO) |
| 42 | cpupri = CPUPRI_NORMAL; |
| 43 | else |
| 44 | cpupri = MAX_RT_PRIO - prio + 1; |
| 45 | |
| 46 | return cpupri; |
| 47 | } |
| 48 | |
| 49 | #define for_each_cpupri_active(array, idx) \ |
| 50 | for (idx = find_first_bit(array, CPUPRI_NR_PRIORITIES); \ |
| 51 | idx < CPUPRI_NR_PRIORITIES; \ |
| 52 | idx = find_next_bit(array, CPUPRI_NR_PRIORITIES, idx+1)) |
| 53 | |
| 54 | /** |
| 55 | * cpupri_find - find the best (lowest-pri) CPU in the system |
| 56 | * @cp: The cpupri context |
| 57 | * @p: The task |
Rusty Russell | 13b8bd0 | 2009-03-25 15:01:22 +1030 | [diff] [blame] | 58 | * @lowest_mask: A mask to fill in with selected CPUs (or NULL) |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 59 | * |
| 60 | * Note: This function returns the recommended CPUs as calculated during the |
| 61 | * current invokation. By the time the call returns, the CPUs may have in |
| 62 | * fact changed priorities any number of times. While not ideal, it is not |
| 63 | * an issue of correctness since the normal rebalancer logic will correct |
| 64 | * any discrepancies created by racing against the uncertainty of the current |
| 65 | * priority configuration. |
| 66 | * |
| 67 | * Returns: (int)bool - CPUs were found |
| 68 | */ |
| 69 | int cpupri_find(struct cpupri *cp, struct task_struct *p, |
Rusty Russell | 68e7456 | 2008-11-25 02:35:13 +1030 | [diff] [blame] | 70 | struct cpumask *lowest_mask) |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 71 | { |
| 72 | int idx = 0; |
| 73 | int task_pri = convert_prio(p->prio); |
| 74 | |
| 75 | for_each_cpupri_active(cp->pri_active, idx) { |
| 76 | struct cpupri_vec *vec = &cp->pri_to_cpu[idx]; |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 77 | |
| 78 | if (idx >= task_pri) |
| 79 | break; |
| 80 | |
Rusty Russell | 68e7456 | 2008-11-25 02:35:13 +1030 | [diff] [blame] | 81 | if (cpumask_any_and(&p->cpus_allowed, vec->mask) >= nr_cpu_ids) |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 82 | continue; |
| 83 | |
Gregory Haskins | 07903af | 2009-07-30 10:57:28 -0400 | [diff] [blame] | 84 | if (lowest_mask) { |
Rusty Russell | 13b8bd0 | 2009-03-25 15:01:22 +1030 | [diff] [blame] | 85 | cpumask_and(lowest_mask, &p->cpus_allowed, vec->mask); |
Gregory Haskins | 07903af | 2009-07-30 10:57:28 -0400 | [diff] [blame] | 86 | |
| 87 | /* |
| 88 | * We have to ensure that we have at least one bit |
| 89 | * still set in the array, since the map could have |
| 90 | * been concurrently emptied between the first and |
| 91 | * second reads of vec->mask. If we hit this |
| 92 | * condition, simply act as though we never hit this |
| 93 | * priority level and continue on. |
| 94 | */ |
| 95 | if (cpumask_any(lowest_mask) >= nr_cpu_ids) |
| 96 | continue; |
| 97 | } |
| 98 | |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 99 | return 1; |
| 100 | } |
| 101 | |
| 102 | return 0; |
| 103 | } |
| 104 | |
| 105 | /** |
| 106 | * cpupri_set - update the cpu priority setting |
| 107 | * @cp: The cpupri context |
| 108 | * @cpu: The target cpu |
| 109 | * @pri: The priority (INVALID-RT99) to assign to this CPU |
| 110 | * |
| 111 | * Note: Assumes cpu_rq(cpu)->lock is locked |
| 112 | * |
| 113 | * Returns: (void) |
| 114 | */ |
| 115 | void cpupri_set(struct cpupri *cp, int cpu, int newpri) |
| 116 | { |
| 117 | int *currpri = &cp->cpu_to_pri[cpu]; |
| 118 | int oldpri = *currpri; |
| 119 | unsigned long flags; |
| 120 | |
| 121 | newpri = convert_prio(newpri); |
| 122 | |
| 123 | BUG_ON(newpri >= CPUPRI_NR_PRIORITIES); |
| 124 | |
| 125 | if (newpri == oldpri) |
| 126 | return; |
| 127 | |
| 128 | /* |
| 129 | * If the cpu was currently mapped to a different value, we |
Steven Rostedt | c3a2ae3 | 2009-07-29 00:21:23 -0400 | [diff] [blame] | 130 | * need to map it to the new value then remove the old value. |
| 131 | * Note, we must add the new value first, otherwise we risk the |
| 132 | * cpu being cleared from pri_active, and this cpu could be |
| 133 | * missed for a push or pull. |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 134 | */ |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 135 | if (likely(newpri != CPUPRI_INVALID)) { |
| 136 | struct cpupri_vec *vec = &cp->pri_to_cpu[newpri]; |
| 137 | |
| 138 | spin_lock_irqsave(&vec->lock, flags); |
| 139 | |
Rusty Russell | 68e7456 | 2008-11-25 02:35:13 +1030 | [diff] [blame] | 140 | cpumask_set_cpu(cpu, vec->mask); |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 141 | vec->count++; |
| 142 | if (vec->count == 1) |
| 143 | set_bit(newpri, cp->pri_active); |
| 144 | |
| 145 | spin_unlock_irqrestore(&vec->lock, flags); |
| 146 | } |
Steven Rostedt | c3a2ae3 | 2009-07-29 00:21:23 -0400 | [diff] [blame] | 147 | if (likely(oldpri != CPUPRI_INVALID)) { |
| 148 | struct cpupri_vec *vec = &cp->pri_to_cpu[oldpri]; |
| 149 | |
| 150 | spin_lock_irqsave(&vec->lock, flags); |
| 151 | |
| 152 | vec->count--; |
| 153 | if (!vec->count) |
| 154 | clear_bit(oldpri, cp->pri_active); |
| 155 | cpumask_clear_cpu(cpu, vec->mask); |
| 156 | |
| 157 | spin_unlock_irqrestore(&vec->lock, flags); |
| 158 | } |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 159 | |
| 160 | *currpri = newpri; |
| 161 | } |
| 162 | |
| 163 | /** |
| 164 | * cpupri_init - initialize the cpupri structure |
| 165 | * @cp: The cpupri context |
Rusty Russell | 68e7456 | 2008-11-25 02:35:13 +1030 | [diff] [blame] | 166 | * @bootmem: true if allocations need to use bootmem |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 167 | * |
Rusty Russell | 68e7456 | 2008-11-25 02:35:13 +1030 | [diff] [blame] | 168 | * Returns: -ENOMEM if memory fails. |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 169 | */ |
Li Zefan | fd5e1b5 | 2009-06-15 13:34:19 +0800 | [diff] [blame] | 170 | int cpupri_init(struct cpupri *cp, bool bootmem) |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 171 | { |
Pekka Enberg | 0fb5302 | 2009-06-11 08:41:22 +0300 | [diff] [blame] | 172 | gfp_t gfp = GFP_KERNEL; |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 173 | int i; |
| 174 | |
Pekka Enberg | 0fb5302 | 2009-06-11 08:41:22 +0300 | [diff] [blame] | 175 | if (bootmem) |
| 176 | gfp = GFP_NOWAIT; |
| 177 | |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 178 | memset(cp, 0, sizeof(*cp)); |
| 179 | |
| 180 | for (i = 0; i < CPUPRI_NR_PRIORITIES; i++) { |
| 181 | struct cpupri_vec *vec = &cp->pri_to_cpu[i]; |
| 182 | |
| 183 | spin_lock_init(&vec->lock); |
| 184 | vec->count = 0; |
Pekka Enberg | 0fb5302 | 2009-06-11 08:41:22 +0300 | [diff] [blame] | 185 | if (!zalloc_cpumask_var(&vec->mask, gfp)) |
Rusty Russell | 68e7456 | 2008-11-25 02:35:13 +1030 | [diff] [blame] | 186 | goto cleanup; |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 187 | } |
| 188 | |
| 189 | for_each_possible_cpu(i) |
| 190 | cp->cpu_to_pri[i] = CPUPRI_INVALID; |
Rusty Russell | 68e7456 | 2008-11-25 02:35:13 +1030 | [diff] [blame] | 191 | return 0; |
| 192 | |
| 193 | cleanup: |
| 194 | for (i--; i >= 0; i--) |
| 195 | free_cpumask_var(cp->pri_to_cpu[i].mask); |
| 196 | return -ENOMEM; |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 197 | } |
| 198 | |
Rusty Russell | 68e7456 | 2008-11-25 02:35:13 +1030 | [diff] [blame] | 199 | /** |
| 200 | * cpupri_cleanup - clean up the cpupri structure |
| 201 | * @cp: The cpupri context |
| 202 | */ |
| 203 | void cpupri_cleanup(struct cpupri *cp) |
| 204 | { |
| 205 | int i; |
Gregory Haskins | 6e0534f | 2008-05-12 21:21:01 +0200 | [diff] [blame] | 206 | |
Rusty Russell | 68e7456 | 2008-11-25 02:35:13 +1030 | [diff] [blame] | 207 | for (i = 0; i < CPUPRI_NR_PRIORITIES; i++) |
| 208 | free_cpumask_var(cp->pri_to_cpu[i].mask); |
| 209 | } |