linux/kernel/profile.c
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   1/*
   2 *  linux/kernel/profile.c
   3 *  Simple profiling. Manages a direct-mapped profile hit count buffer,
   4 *  with configurable resolution, support for restricting the cpus on
   5 *  which profiling is done, and switching between cpu time and
   6 *  schedule() calls via kernel command line parameters passed at boot.
   7 *
   8 *  Scheduler profiling support, Arjan van de Ven and Ingo Molnar,
   9 *      Red Hat, July 2004
  10 *  Consolidation of architecture support code for profiling,
  11 *      Nadia Yvette Chambers, Oracle, July 2004
  12 *  Amortized hit count accounting via per-cpu open-addressed hashtables
  13 *      to resolve timer interrupt livelocks, Nadia Yvette Chambers,
  14 *      Oracle, 2004
  15 */
  16
  17#include <linux/export.h>
  18#include <linux/profile.h>
  19#include <linux/memblock.h>
  20#include <linux/notifier.h>
  21#include <linux/mm.h>
  22#include <linux/cpumask.h>
  23#include <linux/cpu.h>
  24#include <linux/highmem.h>
  25#include <linux/mutex.h>
  26#include <linux/slab.h>
  27#include <linux/vmalloc.h>
  28#include <linux/sched/stat.h>
  29
  30#include <asm/sections.h>
  31#include <asm/irq_regs.h>
  32#include <asm/ptrace.h>
  33
  34struct profile_hit {
  35        u32 pc, hits;
  36};
  37#define PROFILE_GRPSHIFT        3
  38#define PROFILE_GRPSZ           (1 << PROFILE_GRPSHIFT)
  39#define NR_PROFILE_HIT          (PAGE_SIZE/sizeof(struct profile_hit))
  40#define NR_PROFILE_GRP          (NR_PROFILE_HIT/PROFILE_GRPSZ)
  41
  42static atomic_t *prof_buffer;
  43static unsigned long prof_len, prof_shift;
  44
  45int prof_on __read_mostly;
  46EXPORT_SYMBOL_GPL(prof_on);
  47
  48static cpumask_var_t prof_cpu_mask;
  49#if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
  50static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
  51static DEFINE_PER_CPU(int, cpu_profile_flip);
  52static DEFINE_MUTEX(profile_flip_mutex);
  53#endif /* CONFIG_SMP */
  54
  55int profile_setup(char *str)
  56{
  57        static const char schedstr[] = "schedule";
  58        static const char sleepstr[] = "sleep";
  59        static const char kvmstr[] = "kvm";
  60        int par;
  61
  62        if (!strncmp(str, sleepstr, strlen(sleepstr))) {
  63#ifdef CONFIG_SCHEDSTATS
  64                force_schedstat_enabled();
  65                prof_on = SLEEP_PROFILING;
  66                if (str[strlen(sleepstr)] == ',')
  67                        str += strlen(sleepstr) + 1;
  68                if (get_option(&str, &par))
  69                        prof_shift = par;
  70                pr_info("kernel sleep profiling enabled (shift: %ld)\n",
  71                        prof_shift);
  72#else
  73                pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
  74#endif /* CONFIG_SCHEDSTATS */
  75        } else if (!strncmp(str, schedstr, strlen(schedstr))) {
  76                prof_on = SCHED_PROFILING;
  77                if (str[strlen(schedstr)] == ',')
  78                        str += strlen(schedstr) + 1;
  79                if (get_option(&str, &par))
  80                        prof_shift = par;
  81                pr_info("kernel schedule profiling enabled (shift: %ld)\n",
  82                        prof_shift);
  83        } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
  84                prof_on = KVM_PROFILING;
  85                if (str[strlen(kvmstr)] == ',')
  86                        str += strlen(kvmstr) + 1;
  87                if (get_option(&str, &par))
  88                        prof_shift = par;
  89                pr_info("kernel KVM profiling enabled (shift: %ld)\n",
  90                        prof_shift);
  91        } else if (get_option(&str, &par)) {
  92                prof_shift = par;
  93                prof_on = CPU_PROFILING;
  94                pr_info("kernel profiling enabled (shift: %ld)\n",
  95                        prof_shift);
  96        }
  97        return 1;
  98}
  99__setup("profile=", profile_setup);
 100
 101
 102int __ref profile_init(void)
 103{
 104        int buffer_bytes;
 105        if (!prof_on)
 106                return 0;
 107
 108        /* only text is profiled */
 109        prof_len = (_etext - _stext) >> prof_shift;
 110        buffer_bytes = prof_len*sizeof(atomic_t);
 111
 112        if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
 113                return -ENOMEM;
 114
 115        cpumask_copy(prof_cpu_mask, cpu_possible_mask);
 116
 117        prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
 118        if (prof_buffer)
 119                return 0;
 120
 121        prof_buffer = alloc_pages_exact(buffer_bytes,
 122                                        GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
 123        if (prof_buffer)
 124                return 0;
 125
 126        prof_buffer = vzalloc(buffer_bytes);
 127        if (prof_buffer)
 128                return 0;
 129
 130        free_cpumask_var(prof_cpu_mask);
 131        return -ENOMEM;
 132}
 133
 134/* Profile event notifications */
 135
 136static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
 137static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
 138static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
 139
 140void profile_task_exit(struct task_struct *task)
 141{
 142        blocking_notifier_call_chain(&task_exit_notifier, 0, task);
 143}
 144
 145int profile_handoff_task(struct task_struct *task)
 146{
 147        int ret;
 148        ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
 149        return (ret == NOTIFY_OK) ? 1 : 0;
 150}
 151
 152void profile_munmap(unsigned long addr)
 153{
 154        blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
 155}
 156
 157int task_handoff_register(struct notifier_block *n)
 158{
 159        return atomic_notifier_chain_register(&task_free_notifier, n);
 160}
 161EXPORT_SYMBOL_GPL(task_handoff_register);
 162
 163int task_handoff_unregister(struct notifier_block *n)
 164{
 165        return atomic_notifier_chain_unregister(&task_free_notifier, n);
 166}
 167EXPORT_SYMBOL_GPL(task_handoff_unregister);
 168
 169int profile_event_register(enum profile_type type, struct notifier_block *n)
 170{
 171        int err = -EINVAL;
 172
 173        switch (type) {
 174        case PROFILE_TASK_EXIT:
 175                err = blocking_notifier_chain_register(
 176                                &task_exit_notifier, n);
 177                break;
 178        case PROFILE_MUNMAP:
 179                err = blocking_notifier_chain_register(
 180                                &munmap_notifier, n);
 181                break;
 182        }
 183
 184        return err;
 185}
 186EXPORT_SYMBOL_GPL(profile_event_register);
 187
 188int profile_event_unregister(enum profile_type type, struct notifier_block *n)
 189{
 190        int err = -EINVAL;
 191
 192        switch (type) {
 193        case PROFILE_TASK_EXIT:
 194                err = blocking_notifier_chain_unregister(
 195                                &task_exit_notifier, n);
 196                break;
 197        case PROFILE_MUNMAP:
 198                err = blocking_notifier_chain_unregister(
 199                                &munmap_notifier, n);
 200                break;
 201        }
 202
 203        return err;
 204}
 205EXPORT_SYMBOL_GPL(profile_event_unregister);
 206
 207#if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
 208/*
 209 * Each cpu has a pair of open-addressed hashtables for pending
 210 * profile hits. read_profile() IPI's all cpus to request them
 211 * to flip buffers and flushes their contents to prof_buffer itself.
 212 * Flip requests are serialized by the profile_flip_mutex. The sole
 213 * use of having a second hashtable is for avoiding cacheline
 214 * contention that would otherwise happen during flushes of pending
 215 * profile hits required for the accuracy of reported profile hits
 216 * and so resurrect the interrupt livelock issue.
 217 *
 218 * The open-addressed hashtables are indexed by profile buffer slot
 219 * and hold the number of pending hits to that profile buffer slot on
 220 * a cpu in an entry. When the hashtable overflows, all pending hits
 221 * are accounted to their corresponding profile buffer slots with
 222 * atomic_add() and the hashtable emptied. As numerous pending hits
 223 * may be accounted to a profile buffer slot in a hashtable entry,
 224 * this amortizes a number of atomic profile buffer increments likely
 225 * to be far larger than the number of entries in the hashtable,
 226 * particularly given that the number of distinct profile buffer
 227 * positions to which hits are accounted during short intervals (e.g.
 228 * several seconds) is usually very small. Exclusion from buffer
 229 * flipping is provided by interrupt disablement (note that for
 230 * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
 231 * process context).
 232 * The hash function is meant to be lightweight as opposed to strong,
 233 * and was vaguely inspired by ppc64 firmware-supported inverted
 234 * pagetable hash functions, but uses a full hashtable full of finite
 235 * collision chains, not just pairs of them.
 236 *
 237 * -- nyc
 238 */
 239static void __profile_flip_buffers(void *unused)
 240{
 241        int cpu = smp_processor_id();
 242
 243        per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
 244}
 245
 246static void profile_flip_buffers(void)
 247{
 248        int i, j, cpu;
 249
 250        mutex_lock(&profile_flip_mutex);
 251        j = per_cpu(cpu_profile_flip, get_cpu());
 252        put_cpu();
 253        on_each_cpu(__profile_flip_buffers, NULL, 1);
 254        for_each_online_cpu(cpu) {
 255                struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
 256                for (i = 0; i < NR_PROFILE_HIT; ++i) {
 257                        if (!hits[i].hits) {
 258                                if (hits[i].pc)
 259                                        hits[i].pc = 0;
 260                                continue;
 261                        }
 262                        atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 263                        hits[i].hits = hits[i].pc = 0;
 264                }
 265        }
 266        mutex_unlock(&profile_flip_mutex);
 267}
 268
 269static void profile_discard_flip_buffers(void)
 270{
 271        int i, cpu;
 272
 273        mutex_lock(&profile_flip_mutex);
 274        i = per_cpu(cpu_profile_flip, get_cpu());
 275        put_cpu();
 276        on_each_cpu(__profile_flip_buffers, NULL, 1);
 277        for_each_online_cpu(cpu) {
 278                struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
 279                memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
 280        }
 281        mutex_unlock(&profile_flip_mutex);
 282}
 283
 284static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
 285{
 286        unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
 287        int i, j, cpu;
 288        struct profile_hit *hits;
 289
 290        pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
 291        i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 292        secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 293        cpu = get_cpu();
 294        hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
 295        if (!hits) {
 296                put_cpu();
 297                return;
 298        }
 299        /*
 300         * We buffer the global profiler buffer into a per-CPU
 301         * queue and thus reduce the number of global (and possibly
 302         * NUMA-alien) accesses. The write-queue is self-coalescing:
 303         */
 304        local_irq_save(flags);
 305        do {
 306                for (j = 0; j < PROFILE_GRPSZ; ++j) {
 307                        if (hits[i + j].pc == pc) {
 308                                hits[i + j].hits += nr_hits;
 309                                goto out;
 310                        } else if (!hits[i + j].hits) {
 311                                hits[i + j].pc = pc;
 312                                hits[i + j].hits = nr_hits;
 313                                goto out;
 314                        }
 315                }
 316                i = (i + secondary) & (NR_PROFILE_HIT - 1);
 317        } while (i != primary);
 318
 319        /*
 320         * Add the current hit(s) and flush the write-queue out
 321         * to the global buffer:
 322         */
 323        atomic_add(nr_hits, &prof_buffer[pc]);
 324        for (i = 0; i < NR_PROFILE_HIT; ++i) {
 325                atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 326                hits[i].pc = hits[i].hits = 0;
 327        }
 328out:
 329        local_irq_restore(flags);
 330        put_cpu();
 331}
 332
 333static int profile_dead_cpu(unsigned int cpu)
 334{
 335        struct page *page;
 336        int i;
 337
 338        if (prof_cpu_mask != NULL)
 339                cpumask_clear_cpu(cpu, prof_cpu_mask);
 340
 341        for (i = 0; i < 2; i++) {
 342                if (per_cpu(cpu_profile_hits, cpu)[i]) {
 343                        page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[i]);
 344                        per_cpu(cpu_profile_hits, cpu)[i] = NULL;
 345                        __free_page(page);
 346                }
 347        }
 348        return 0;
 349}
 350
 351static int profile_prepare_cpu(unsigned int cpu)
 352{
 353        int i, node = cpu_to_mem(cpu);
 354        struct page *page;
 355
 356        per_cpu(cpu_profile_flip, cpu) = 0;
 357
 358        for (i = 0; i < 2; i++) {
 359                if (per_cpu(cpu_profile_hits, cpu)[i])
 360                        continue;
 361
 362                page = __alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
 363                if (!page) {
 364                        profile_dead_cpu(cpu);
 365                        return -ENOMEM;
 366                }
 367                per_cpu(cpu_profile_hits, cpu)[i] = page_address(page);
 368
 369        }
 370        return 0;
 371}
 372
 373static int profile_online_cpu(unsigned int cpu)
 374{
 375        if (prof_cpu_mask != NULL)
 376                cpumask_set_cpu(cpu, prof_cpu_mask);
 377
 378        return 0;
 379}
 380
 381#else /* !CONFIG_SMP */
 382#define profile_flip_buffers()          do { } while (0)
 383#define profile_discard_flip_buffers()  do { } while (0)
 384
 385static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
 386{
 387        unsigned long pc;
 388        pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
 389        atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
 390}
 391#endif /* !CONFIG_SMP */
 392
 393void profile_hits(int type, void *__pc, unsigned int nr_hits)
 394{
 395        if (prof_on != type || !prof_buffer)
 396                return;
 397        do_profile_hits(type, __pc, nr_hits);
 398}
 399EXPORT_SYMBOL_GPL(profile_hits);
 400
 401void profile_tick(int type)
 402{
 403        struct pt_regs *regs = get_irq_regs();
 404
 405        if (!user_mode(regs) && prof_cpu_mask != NULL &&
 406            cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
 407                profile_hit(type, (void *)profile_pc(regs));
 408}
 409
 410#ifdef CONFIG_PROC_FS
 411#include <linux/proc_fs.h>
 412#include <linux/seq_file.h>
 413#include <linux/uaccess.h>
 414
 415static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
 416{
 417        seq_printf(m, "%*pb\n", cpumask_pr_args(prof_cpu_mask));
 418        return 0;
 419}
 420
 421static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
 422{
 423        return single_open(file, prof_cpu_mask_proc_show, NULL);
 424}
 425
 426static ssize_t prof_cpu_mask_proc_write(struct file *file,
 427        const char __user *buffer, size_t count, loff_t *pos)
 428{
 429        cpumask_var_t new_value;
 430        int err;
 431
 432        if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
 433                return -ENOMEM;
 434
 435        err = cpumask_parse_user(buffer, count, new_value);
 436        if (!err) {
 437                cpumask_copy(prof_cpu_mask, new_value);
 438                err = count;
 439        }
 440        free_cpumask_var(new_value);
 441        return err;
 442}
 443
 444static const struct file_operations prof_cpu_mask_proc_fops = {
 445        .open           = prof_cpu_mask_proc_open,
 446        .read           = seq_read,
 447        .llseek         = seq_lseek,
 448        .release        = single_release,
 449        .write          = prof_cpu_mask_proc_write,
 450};
 451
 452void create_prof_cpu_mask(void)
 453{
 454        /* create /proc/irq/prof_cpu_mask */
 455        proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_fops);
 456}
 457
 458/*
 459 * This function accesses profiling information. The returned data is
 460 * binary: the sampling step and the actual contents of the profile
 461 * buffer. Use of the program readprofile is recommended in order to
 462 * get meaningful info out of these data.
 463 */
 464static ssize_t
 465read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 466{
 467        unsigned long p = *ppos;
 468        ssize_t read;
 469        char *pnt;
 470        unsigned int sample_step = 1 << prof_shift;
 471
 472        profile_flip_buffers();
 473        if (p >= (prof_len+1)*sizeof(unsigned int))
 474                return 0;
 475        if (count > (prof_len+1)*sizeof(unsigned int) - p)
 476                count = (prof_len+1)*sizeof(unsigned int) - p;
 477        read = 0;
 478
 479        while (p < sizeof(unsigned int) && count > 0) {
 480                if (put_user(*((char *)(&sample_step)+p), buf))
 481                        return -EFAULT;
 482                buf++; p++; count--; read++;
 483        }
 484        pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 485        if (copy_to_user(buf, (void *)pnt, count))
 486                return -EFAULT;
 487        read += count;
 488        *ppos += read;
 489        return read;
 490}
 491
 492/*
 493 * Writing to /proc/profile resets the counters
 494 *
 495 * Writing a 'profiling multiplier' value into it also re-sets the profiling
 496 * interrupt frequency, on architectures that support this.
 497 */
 498static ssize_t write_profile(struct file *file, const char __user *buf,
 499                             size_t count, loff_t *ppos)
 500{
 501#ifdef CONFIG_SMP
 502        extern int setup_profiling_timer(unsigned int multiplier);
 503
 504        if (count == sizeof(int)) {
 505                unsigned int multiplier;
 506
 507                if (copy_from_user(&multiplier, buf, sizeof(int)))
 508                        return -EFAULT;
 509
 510                if (setup_profiling_timer(multiplier))
 511                        return -EINVAL;
 512        }
 513#endif
 514        profile_discard_flip_buffers();
 515        memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 516        return count;
 517}
 518
 519static const struct file_operations proc_profile_operations = {
 520        .read           = read_profile,
 521        .write          = write_profile,
 522        .llseek         = default_llseek,
 523};
 524
 525int __ref create_proc_profile(void)
 526{
 527        struct proc_dir_entry *entry;
 528#ifdef CONFIG_SMP
 529        enum cpuhp_state online_state;
 530#endif
 531
 532        int err = 0;
 533
 534        if (!prof_on)
 535                return 0;
 536#ifdef CONFIG_SMP
 537        err = cpuhp_setup_state(CPUHP_PROFILE_PREPARE, "PROFILE_PREPARE",
 538                                profile_prepare_cpu, profile_dead_cpu);
 539        if (err)
 540                return err;
 541
 542        err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "AP_PROFILE_ONLINE",
 543                                profile_online_cpu, NULL);
 544        if (err < 0)
 545                goto err_state_prep;
 546        online_state = err;
 547        err = 0;
 548#endif
 549        entry = proc_create("profile", S_IWUSR | S_IRUGO,
 550                            NULL, &proc_profile_operations);
 551        if (!entry)
 552                goto err_state_onl;
 553        proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
 554
 555        return err;
 556err_state_onl:
 557#ifdef CONFIG_SMP
 558        cpuhp_remove_state(online_state);
 559err_state_prep:
 560        cpuhp_remove_state(CPUHP_PROFILE_PREPARE);
 561#endif
 562        return err;
 563}
 564subsys_initcall(create_proc_profile);
 565#endif /* CONFIG_PROC_FS */
 566