1 /* 2 * latencytop.c: Latency display infrastructure 3 * 4 * (C) Copyright 2008 Intel Corporation 5 * Author: Arjan van de Ven <arjan@linux.intel.com> 6 * 7 * This program is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU General Public License 9 * as published by the Free Software Foundation; version 2 10 * of the License. 11 */ 12 #include <linux/latencytop.h> 13 #include <linux/kallsyms.h> 14 #include <linux/seq_file.h> 15 #include <linux/notifier.h> 16 #include <linux/spinlock.h> 17 #include <linux/proc_fs.h> 18 #include <linux/module.h> 19 #include <linux/sched.h> 20 #include <linux/list.h> 21 #include <linux/slab.h> 22 #include <linux/stacktrace.h> 23 24 static DEFINE_SPINLOCK(latency_lock); 25 26 #define MAXLR 128 27 static struct latency_record latency_record[MAXLR]; 28 29 int latencytop_enabled; 30 31 void clear_all_latency_tracing(struct task_struct *p) 32 { 33 unsigned long flags; 34 35 if (!latencytop_enabled) 36 return; 37 38 spin_lock_irqsave(&latency_lock, flags); 39 memset(&p->latency_record, 0, sizeof(p->latency_record)); 40 p->latency_record_count = 0; 41 spin_unlock_irqrestore(&latency_lock, flags); 42 } 43 44 static void clear_global_latency_tracing(void) 45 { 46 unsigned long flags; 47 48 spin_lock_irqsave(&latency_lock, flags); 49 memset(&latency_record, 0, sizeof(latency_record)); 50 spin_unlock_irqrestore(&latency_lock, flags); 51 } 52 53 static void __sched 54 account_global_scheduler_latency(struct task_struct *tsk, struct latency_record *lat) 55 { 56 int firstnonnull = MAXLR + 1; 57 int i; 58 59 if (!latencytop_enabled) 60 return; 61 62 /* skip kernel threads for now */ 63 if (!tsk->mm) 64 return; 65 66 for (i = 0; i < MAXLR; i++) { 67 int q; 68 int same = 1; 69 /* Nothing stored: */ 70 if (!latency_record[i].backtrace[0]) { 71 if (firstnonnull > i) 72 firstnonnull = i; 73 continue; 74 } 75 for (q = 0 ; q < LT_BACKTRACEDEPTH ; q++) { 76 if (latency_record[i].backtrace[q] != 77 lat->backtrace[q]) 78 same = 0; 79 if (same && lat->backtrace[q] == 0) 80 break; 81 if (same && lat->backtrace[q] == ULONG_MAX) 82 break; 83 } 84 if (same) { 85 latency_record[i].count++; 86 latency_record[i].time += lat->time; 87 if (lat->time > latency_record[i].max) 88 latency_record[i].max = lat->time; 89 return; 90 } 91 } 92 93 i = firstnonnull; 94 if (i >= MAXLR - 1) 95 return; 96 97 /* Allocted a new one: */ 98 memcpy(&latency_record[i], lat, sizeof(struct latency_record)); 99 } 100 101 static inline void store_stacktrace(struct task_struct *tsk, struct latency_record *lat) 102 { 103 struct stack_trace trace; 104 105 memset(&trace, 0, sizeof(trace)); 106 trace.max_entries = LT_BACKTRACEDEPTH; 107 trace.entries = &lat->backtrace[0]; 108 trace.skip = 0; 109 save_stack_trace_tsk(tsk, &trace); 110 } 111 112 void __sched 113 account_scheduler_latency(struct task_struct *tsk, int usecs, int inter) 114 { 115 unsigned long flags; 116 int i, q; 117 struct latency_record lat; 118 119 if (!latencytop_enabled) 120 return; 121 122 /* Long interruptible waits are generally user requested... */ 123 if (inter && usecs > 5000) 124 return; 125 126 memset(&lat, 0, sizeof(lat)); 127 lat.count = 1; 128 lat.time = usecs; 129 lat.max = usecs; 130 store_stacktrace(tsk, &lat); 131 132 spin_lock_irqsave(&latency_lock, flags); 133 134 account_global_scheduler_latency(tsk, &lat); 135 136 /* 137 * short term hack; if we're > 32 we stop; future we recycle: 138 */ 139 tsk->latency_record_count++; 140 if (tsk->latency_record_count >= LT_SAVECOUNT) 141 goto out_unlock; 142 143 for (i = 0; i < LT_SAVECOUNT ; i++) { 144 struct latency_record *mylat; 145 int same = 1; 146 mylat = &tsk->latency_record[i]; 147 for (q = 0 ; q < LT_BACKTRACEDEPTH ; q++) { 148 if (mylat->backtrace[q] != 149 lat.backtrace[q]) 150 same = 0; 151 if (same && lat.backtrace[q] == 0) 152 break; 153 if (same && lat.backtrace[q] == ULONG_MAX) 154 break; 155 } 156 if (same) { 157 mylat->count++; 158 mylat->time += lat.time; 159 if (lat.time > mylat->max) 160 mylat->max = lat.time; 161 goto out_unlock; 162 } 163 } 164 165 /* Allocated a new one: */ 166 i = tsk->latency_record_count; 167 memcpy(&tsk->latency_record[i], &lat, sizeof(struct latency_record)); 168 169 out_unlock: 170 spin_unlock_irqrestore(&latency_lock, flags); 171 } 172 173 static int lstats_show(struct seq_file *m, void *v) 174 { 175 int i; 176 177 seq_puts(m, "Latency Top version : v0.1\n"); 178 179 for (i = 0; i < MAXLR; i++) { 180 if (latency_record[i].backtrace[0]) { 181 int q; 182 seq_printf(m, "%i %li %li ", 183 latency_record[i].count, 184 latency_record[i].time, 185 latency_record[i].max); 186 for (q = 0; q < LT_BACKTRACEDEPTH; q++) { 187 char sym[KSYM_NAME_LEN]; 188 char *c; 189 if (!latency_record[i].backtrace[q]) 190 break; 191 if (latency_record[i].backtrace[q] == ULONG_MAX) 192 break; 193 sprint_symbol(sym, latency_record[i].backtrace[q]); 194 c = strchr(sym, '+'); 195 if (c) 196 *c = 0; 197 seq_printf(m, "%s ", sym); 198 } 199 seq_printf(m, "\n"); 200 } 201 } 202 return 0; 203 } 204 205 static ssize_t 206 lstats_write(struct file *file, const char __user *buf, size_t count, 207 loff_t *offs) 208 { 209 clear_global_latency_tracing(); 210 211 return count; 212 } 213 214 static int lstats_open(struct inode *inode, struct file *filp) 215 { 216 return single_open(filp, lstats_show, NULL); 217 } 218 219 static struct file_operations lstats_fops = { 220 .open = lstats_open, 221 .read = seq_read, 222 .write = lstats_write, 223 .llseek = seq_lseek, 224 .release = single_release, 225 }; 226 227 static int __init init_lstats_procfs(void) 228 { 229 struct proc_dir_entry *pe; 230 231 pe = create_proc_entry("latency_stats", 0644, NULL); 232 if (!pe) 233 return -ENOMEM; 234 235 pe->proc_fops = &lstats_fops; 236 237 return 0; 238 } 239 __initcall(init_lstats_procfs); 240