| 1 | /* test-cmpxchg-nolock.c |
| 2 | * |
| 3 | * Compare local cmpxchg with irq disable / enable. |
| 4 | */ |
| 5 | |
| 6 | |
| 7 | #include <linux/jiffies.h> |
| 8 | #include <linux/compiler.h> |
| 9 | #include <linux/init.h> |
| 10 | #include <linux/module.h> |
| 11 | #include <linux/math64.h> |
| 12 | #include <asm/timex.h> |
| 13 | #include <asm/system.h> |
| 14 | |
| 15 | #define NR_LOOPS 20000 |
| 16 | |
| 17 | int test_val; |
| 18 | |
| 19 | static void do_testbaseline(void) |
| 20 | { |
| 21 | unsigned long flags; |
| 22 | unsigned int i; |
| 23 | cycles_t time1, time2, time; |
| 24 | u32 rem; |
| 25 | |
| 26 | local_irq_save(flags); |
| 27 | preempt_disable(); |
| 28 | time1 = get_cycles(); |
| 29 | for (i = 0; i < NR_LOOPS; i++) { |
| 30 | asm volatile (""); |
| 31 | } |
| 32 | time2 = get_cycles(); |
| 33 | local_irq_restore(flags); |
| 34 | preempt_enable(); |
| 35 | time = time2 - time1; |
| 36 | |
| 37 | printk(KERN_ALERT "test results: time for baseline\n"); |
| 38 | printk(KERN_ALERT "number of loops: %d\n", NR_LOOPS); |
| 39 | printk(KERN_ALERT "total time: %llu\n", time); |
| 40 | time = div_u64_rem(time, NR_LOOPS, &rem); |
| 41 | printk(KERN_ALERT "-> baseline takes %llu cycles\n", time); |
| 42 | printk(KERN_ALERT "test end\n"); |
| 43 | } |
| 44 | |
| 45 | static void do_test_sync_cmpxchg(void) |
| 46 | { |
| 47 | int ret; |
| 48 | unsigned long flags; |
| 49 | unsigned int i; |
| 50 | cycles_t time1, time2, time; |
| 51 | u32 rem; |
| 52 | |
| 53 | local_irq_save(flags); |
| 54 | preempt_disable(); |
| 55 | time1 = get_cycles(); |
| 56 | for (i = 0; i < NR_LOOPS; i++) { |
| 57 | #ifdef CONFIG_X86_32 |
| 58 | ret = sync_cmpxchg(&test_val, 0, 0); |
| 59 | #else |
| 60 | ret = cmpxchg(&test_val, 0, 0); |
| 61 | #endif |
| 62 | } |
| 63 | time2 = get_cycles(); |
| 64 | local_irq_restore(flags); |
| 65 | preempt_enable(); |
| 66 | time = time2 - time1; |
| 67 | |
| 68 | printk(KERN_ALERT "test results: time for locked cmpxchg\n"); |
| 69 | printk(KERN_ALERT "number of loops: %d\n", NR_LOOPS); |
| 70 | printk(KERN_ALERT "total time: %llu\n", time); |
| 71 | time = div_u64_rem(time, NR_LOOPS, &rem); |
| 72 | printk(KERN_ALERT "-> locked cmpxchg takes %llu cycles\n", time); |
| 73 | printk(KERN_ALERT "test end\n"); |
| 74 | } |
| 75 | |
| 76 | static void do_test_cmpxchg(void) |
| 77 | { |
| 78 | int ret; |
| 79 | unsigned long flags; |
| 80 | unsigned int i; |
| 81 | cycles_t time1, time2, time; |
| 82 | u32 rem; |
| 83 | |
| 84 | local_irq_save(flags); |
| 85 | preempt_disable(); |
| 86 | time1 = get_cycles(); |
| 87 | for (i = 0; i < NR_LOOPS; i++) { |
| 88 | ret = cmpxchg_local(&test_val, 0, 0); |
| 89 | } |
| 90 | time2 = get_cycles(); |
| 91 | local_irq_restore(flags); |
| 92 | preempt_enable(); |
| 93 | time = time2 - time1; |
| 94 | |
| 95 | printk(KERN_ALERT "test results: time for non locked cmpxchg\n"); |
| 96 | printk(KERN_ALERT "number of loops: %d\n", NR_LOOPS); |
| 97 | printk(KERN_ALERT "total time: %llu\n", time); |
| 98 | time = div_u64_rem(time, NR_LOOPS, &rem); |
| 99 | printk(KERN_ALERT "-> non locked cmpxchg takes %llu cycles\n", time); |
| 100 | printk(KERN_ALERT "test end\n"); |
| 101 | } |
| 102 | static void do_test_sync_inc(void) |
| 103 | { |
| 104 | int ret; |
| 105 | unsigned long flags; |
| 106 | unsigned int i; |
| 107 | cycles_t time1, time2, time; |
| 108 | u32 rem; |
| 109 | atomic_t val; |
| 110 | |
| 111 | local_irq_save(flags); |
| 112 | preempt_disable(); |
| 113 | time1 = get_cycles(); |
| 114 | for (i = 0; i < NR_LOOPS; i++) { |
| 115 | ret = atomic_add_return(10, &val); |
| 116 | } |
| 117 | time2 = get_cycles(); |
| 118 | local_irq_restore(flags); |
| 119 | preempt_enable(); |
| 120 | time = time2 - time1; |
| 121 | |
| 122 | printk(KERN_ALERT "test results: time for locked add return\n"); |
| 123 | printk(KERN_ALERT "number of loops: %d\n", NR_LOOPS); |
| 124 | printk(KERN_ALERT "total time: %llu\n", time); |
| 125 | time = div_u64_rem(time, NR_LOOPS, &rem); |
| 126 | printk(KERN_ALERT "-> locked add return takes %llu cycles\n", time); |
| 127 | printk(KERN_ALERT "test end\n"); |
| 128 | } |
| 129 | |
| 130 | |
| 131 | static void do_test_inc(void) |
| 132 | { |
| 133 | int ret; |
| 134 | unsigned long flags; |
| 135 | unsigned int i; |
| 136 | cycles_t time1, time2, time; |
| 137 | u32 rem; |
| 138 | local_t loc_val; |
| 139 | |
| 140 | local_irq_save(flags); |
| 141 | preempt_disable(); |
| 142 | time1 = get_cycles(); |
| 143 | for (i = 0; i < NR_LOOPS; i++) { |
| 144 | ret = local_add_return(10, &loc_val); |
| 145 | } |
| 146 | time2 = get_cycles(); |
| 147 | local_irq_restore(flags); |
| 148 | preempt_enable(); |
| 149 | time = time2 - time1; |
| 150 | |
| 151 | printk(KERN_ALERT "test results: time for non locked add return\n"); |
| 152 | printk(KERN_ALERT "number of loops: %d\n", NR_LOOPS); |
| 153 | printk(KERN_ALERT "total time: %llu\n", time); |
| 154 | time = div_u64_rem(time, NR_LOOPS, &rem); |
| 155 | printk(KERN_ALERT "-> non locked add return takes %llu cycles\n", time); |
| 156 | printk(KERN_ALERT "test end\n"); |
| 157 | } |
| 158 | |
| 159 | |
| 160 | |
| 161 | /* |
| 162 | * This test will have a higher standard deviation due to incoming interrupts. |
| 163 | */ |
| 164 | static void do_test_enable_int(void) |
| 165 | { |
| 166 | unsigned long flags; |
| 167 | unsigned int i; |
| 168 | cycles_t time1, time2, time; |
| 169 | u32 rem; |
| 170 | |
| 171 | local_irq_save(flags); |
| 172 | preempt_disable(); |
| 173 | time1 = get_cycles(); |
| 174 | for (i = 0; i < NR_LOOPS; i++) { |
| 175 | local_irq_restore(flags); |
| 176 | } |
| 177 | time2 = get_cycles(); |
| 178 | local_irq_restore(flags); |
| 179 | preempt_enable(); |
| 180 | time = time2 - time1; |
| 181 | |
| 182 | printk(KERN_ALERT "test results: time for enabling interrupts (STI)\n"); |
| 183 | printk(KERN_ALERT "number of loops: %d\n", NR_LOOPS); |
| 184 | printk(KERN_ALERT "total time: %llu\n", time); |
| 185 | time = div_u64_rem(time, NR_LOOPS, &rem); |
| 186 | printk(KERN_ALERT "-> enabling interrupts (STI) takes %llu cycles\n", |
| 187 | time); |
| 188 | printk(KERN_ALERT "test end\n"); |
| 189 | } |
| 190 | |
| 191 | static void do_test_disable_int(void) |
| 192 | { |
| 193 | unsigned long flags, flags2; |
| 194 | unsigned int i; |
| 195 | cycles_t time1, time2, time; |
| 196 | u32 rem; |
| 197 | |
| 198 | local_irq_save(flags); |
| 199 | preempt_disable(); |
| 200 | time1 = get_cycles(); |
| 201 | for ( i = 0; i < NR_LOOPS; i++) { |
| 202 | local_irq_save(flags2); |
| 203 | } |
| 204 | time2 = get_cycles(); |
| 205 | local_irq_restore(flags); |
| 206 | preempt_enable(); |
| 207 | time = time2 - time1; |
| 208 | |
| 209 | printk(KERN_ALERT "test results: time for disabling interrupts (CLI)\n"); |
| 210 | printk(KERN_ALERT "number of loops: %d\n", NR_LOOPS); |
| 211 | printk(KERN_ALERT "total time: %llu\n", time); |
| 212 | time = div_u64_rem(time, NR_LOOPS, &rem); |
| 213 | printk(KERN_ALERT "-> disabling interrupts (CLI) takes %llu cycles\n", |
| 214 | time); |
| 215 | printk(KERN_ALERT "test end\n"); |
| 216 | } |
| 217 | |
| 218 | static void do_test_int(void) |
| 219 | { |
| 220 | unsigned long flags; |
| 221 | unsigned int i; |
| 222 | cycles_t time1, time2, time; |
| 223 | u32 rem; |
| 224 | |
| 225 | local_irq_save(flags); |
| 226 | preempt_disable(); |
| 227 | time1 = get_cycles(); |
| 228 | for (i = 0; i < NR_LOOPS; i++) { |
| 229 | local_irq_restore(flags); |
| 230 | local_irq_save(flags); |
| 231 | } |
| 232 | time2 = get_cycles(); |
| 233 | local_irq_restore(flags); |
| 234 | preempt_enable(); |
| 235 | time = time2 - time1; |
| 236 | |
| 237 | printk(KERN_ALERT "test results: time for disabling/enabling interrupts (STI/CLI)\n"); |
| 238 | printk(KERN_ALERT "number of loops: %d\n", NR_LOOPS); |
| 239 | printk(KERN_ALERT "total time: %llu\n", time); |
| 240 | time = div_u64_rem(time, NR_LOOPS, &rem); |
| 241 | printk(KERN_ALERT "-> enabling/disabling interrupts (STI/CLI) takes %llu cycles\n", |
| 242 | time); |
| 243 | printk(KERN_ALERT "test end\n"); |
| 244 | } |
| 245 | |
| 246 | |
| 247 | |
| 248 | static int ltt_test_init(void) |
| 249 | { |
| 250 | printk(KERN_ALERT "test init\n"); |
| 251 | |
| 252 | do_testbaseline(); |
| 253 | do_test_sync_cmpxchg(); |
| 254 | do_test_cmpxchg(); |
| 255 | do_test_sync_inc(); |
| 256 | do_test_inc(); |
| 257 | do_test_enable_int(); |
| 258 | do_test_disable_int(); |
| 259 | do_test_int(); |
| 260 | return -EAGAIN; /* Fail will directly unload the module */ |
| 261 | } |
| 262 | |
| 263 | static void ltt_test_exit(void) |
| 264 | { |
| 265 | printk(KERN_ALERT "test exit\n"); |
| 266 | } |
| 267 | |
| 268 | module_init(ltt_test_init) |
| 269 | module_exit(ltt_test_exit) |
| 270 | |
| 271 | MODULE_LICENSE("GPL"); |
| 272 | MODULE_AUTHOR("Mathieu Desnoyers"); |
| 273 | MODULE_DESCRIPTION("Cmpxchg vs int Test"); |
| 274 | |