| 421991b0 |
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/calc64.h> |
| 12 | #include <asm/timex.h> |
| 13 | #include <asm/system.h> |
| 14 | |
| 15 | #define NR_LOOPS 20000 |
| 16 | |
| 17 | int test_val; |
| 18 | |
| f57afc80 |
19 | static void do_test_sync_cmpxchg(void) |
| 20 | { |
| 21 | int ret; |
| 22 | long flags; |
| 23 | unsigned int i; |
| 24 | cycles_t time1, time2, time; |
| 25 | long rem; |
| 26 | |
| 27 | local_irq_save(flags); |
| 28 | preempt_disable(); |
| 29 | time1 = get_cycles(); |
| 30 | for (i = 0; i < NR_LOOPS; i++) { |
| 31 | #ifdef CONFIG_X86_32 |
| 32 | ret = sync_cmpxchg(&test_val, 0, 0); |
| 33 | #else |
| 34 | ret = cmpxchg(&test_val, 0, 0); |
| 35 | #endif |
| 36 | } |
| 37 | time2 = get_cycles(); |
| 38 | local_irq_restore(flags); |
| 39 | preempt_enable(); |
| 40 | time = time2 - time1; |
| 41 | |
| 42 | printk(KERN_ALERT "test results: time for locked cmpxchg\n"); |
| 43 | printk(KERN_ALERT "number of loops: %d\n", NR_LOOPS); |
| 44 | printk(KERN_ALERT "total time: %llu\n", time); |
| 45 | time = div_long_long_rem(time, NR_LOOPS, &rem); |
| 46 | printk(KERN_ALERT "-> locked cmpxchg takes %llu cycles\n", time); |
| 47 | printk(KERN_ALERT "test end\n"); |
| 48 | } |
| 49 | |
| 421991b0 |
50 | static void do_test_cmpxchg(void) |
| 51 | { |
| 52 | int ret; |
| 53 | long flags; |
| 54 | unsigned int i; |
| 55 | cycles_t time1, time2, time; |
| 56 | long rem; |
| 57 | |
| 58 | local_irq_save(flags); |
| 59 | preempt_disable(); |
| 60 | time1 = get_cycles(); |
| 61 | for (i = 0; i < NR_LOOPS; i++) { |
| 62 | ret = cmpxchg_local(&test_val, 0, 0); |
| 63 | } |
| 64 | time2 = get_cycles(); |
| 65 | local_irq_restore(flags); |
| 66 | preempt_enable(); |
| 67 | time = time2 - time1; |
| 68 | |
| 69 | printk(KERN_ALERT "test results: time for non locked cmpxchg\n"); |
| 70 | printk(KERN_ALERT "number of loops: %d\n", NR_LOOPS); |
| 71 | printk(KERN_ALERT "total time: %llu\n", time); |
| 72 | time = div_long_long_rem(time, NR_LOOPS, &rem); |
| 73 | printk(KERN_ALERT "-> non locked cmpxchg takes %llu cycles\n", time); |
| 74 | printk(KERN_ALERT "test end\n"); |
| 75 | } |
| 76 | |
| 77 | /* |
| 78 | * This test will have a higher standard deviation due to incoming interrupts. |
| 79 | */ |
| 80 | static void do_test_enable_int(void) |
| 81 | { |
| 82 | long flags; |
| 83 | unsigned int i; |
| 84 | cycles_t time1, time2, time; |
| 85 | long rem; |
| 86 | |
| 87 | local_irq_save(flags); |
| 88 | preempt_disable(); |
| 89 | time1 = get_cycles(); |
| 90 | for (i = 0; i < NR_LOOPS; i++) { |
| 91 | local_irq_restore(flags); |
| 92 | } |
| 93 | time2 = get_cycles(); |
| 94 | local_irq_restore(flags); |
| 95 | preempt_enable(); |
| 96 | time = time2 - time1; |
| 97 | |
| 98 | printk(KERN_ALERT "test results: time for enabling interrupts (STI)\n"); |
| 99 | printk(KERN_ALERT "number of loops: %d\n", NR_LOOPS); |
| 100 | printk(KERN_ALERT "total time: %llu\n", time); |
| 101 | time = div_long_long_rem(time, NR_LOOPS, &rem); |
| 102 | printk(KERN_ALERT "-> enabling interrupts (STI) takes %llu cycles\n", |
| 103 | time); |
| 104 | printk(KERN_ALERT "test end\n"); |
| 105 | } |
| 106 | |
| 107 | static void do_test_disable_int(void) |
| 108 | { |
| 109 | unsigned long flags, flags2; |
| 110 | unsigned int i; |
| 111 | cycles_t time1, time2, time; |
| 112 | long rem; |
| 113 | |
| 114 | local_irq_save(flags); |
| 115 | preempt_disable(); |
| 116 | time1 = get_cycles(); |
| 117 | for ( i = 0; i < NR_LOOPS; i++) { |
| 118 | local_irq_save(flags2); |
| 119 | } |
| 120 | time2 = get_cycles(); |
| 121 | local_irq_restore(flags); |
| 122 | preempt_enable(); |
| 123 | time = time2 - time1; |
| 124 | |
| 125 | printk(KERN_ALERT "test results: time for disabling interrupts (CLI)\n"); |
| 126 | printk(KERN_ALERT "number of loops: %d\n", NR_LOOPS); |
| 127 | printk(KERN_ALERT "total time: %llu\n", time); |
| 128 | time = div_long_long_rem(time, NR_LOOPS, &rem); |
| 7de49e3a |
129 | printk(KERN_ALERT "-> disabling interrupts (CLI) takes %llu cycles\n", |
| 421991b0 |
130 | time); |
| 131 | printk(KERN_ALERT "test end\n"); |
| 132 | } |
| 133 | |
| 134 | |
| 135 | |
| 136 | static int ltt_test_init(void) |
| 137 | { |
| 138 | printk(KERN_ALERT "test init\n"); |
| 139 | |
| fa2b47dd |
140 | do_test_sync_cmpxchg(); |
| 421991b0 |
141 | do_test_cmpxchg(); |
| 142 | do_test_enable_int(); |
| 143 | do_test_disable_int(); |
| 144 | return -EAGAIN; /* Fail will directly unload the module */ |
| 145 | } |
| 146 | |
| 147 | static void ltt_test_exit(void) |
| 148 | { |
| 149 | printk(KERN_ALERT "test exit\n"); |
| 150 | } |
| 151 | |
| 152 | module_init(ltt_test_init) |
| 153 | module_exit(ltt_test_exit) |
| 154 | |
| 155 | MODULE_LICENSE("GPL"); |
| 156 | MODULE_AUTHOR("Mathieu Desnoyers"); |
| 157 | MODULE_DESCRIPTION("Cmpxchg vs int Test"); |
| 158 | |
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