profile.c

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/*
 *  linux/kernel/profile.c
 *  Simple profiling. Manages a direct-mapped profile hit count buffer,
 *  with configurable resolution, support for restricting the cpus on
 *  which profiling is done, and switching between cpu time and
 *  schedule() calls via kernel command line parameters passed at boot.
 *
 *  Scheduler profiling support, Arjan van de Ven and Ingo Molnar,
 *  Red Hat, July 2004
 *  Consolidation of architecture support code for profiling,
 *  William Irwin, Oracle, July 2004
 *  Amortized hit count accounting via per-cpu open-addressed hashtables
 *  to resolve timer interrupt livelocks, William Irwin, Oracle, 2004
 */

#include <linux/export.h>
#include <linux/profile.h>
#include <linux/bootmem.h>
#include <linux/notifier.h>
#include <linux/mm.h>
#include <linux/cpumask.h>
#include <linux/cpu.h>
#include <linux/highmem.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <asm/sections.h>
#include <asm/irq_regs.h>
#include <asm/ptrace.h>

struct profile_hit {
    u32 pc, hits;
};
#define PROFILE_GRPSHIFT    3
#define PROFILE_GRPSZ       (1 << PROFILE_GRPSHIFT)
#define NR_PROFILE_HIT      (PAGE_SIZE/sizeof(struct profile_hit))
#define NR_PROFILE_GRP      (NR_PROFILE_HIT/PROFILE_GRPSZ)

/* Oprofile timer tick hook */
static int (*timer_hook)(struct pt_regs *) __read_mostly;

static atomic_t *prof_buffer;
static unsigned long prof_len, prof_shift;

int prof_on __read_mostly;
EXPORT_SYMBOL_GPL(prof_on);

static cpumask_var_t prof_cpu_mask;
#ifdef CONFIG_SMP
static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
static DEFINE_PER_CPU(int, cpu_profile_flip);
static DEFINE_MUTEX(profile_flip_mutex);
#endif /* CONFIG_SMP */

int profile_setup(char *str)
{
    static char schedstr[] = "schedule";
    static char sleepstr[] = "sleep";
    static char kvmstr[] = "kvm";
    int par;

    if (!strncmp(str, sleepstr, strlen(sleepstr))) {
#ifdef CONFIG_SCHEDSTATS
        prof_on = SLEEP_PROFILING;
        if (str[strlen(sleepstr)] == ',')
            str += strlen(sleepstr) + 1;
        if (get_option(&str, &par))
            prof_shift = par;
        printk(KERN_INFO
            "kernel sleep profiling enabled (shift: %ld)\n",
            prof_shift);
#else
        printk(KERN_WARNING
            "kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
#endif /* CONFIG_SCHEDSTATS */
    } else if (!strncmp(str, schedstr, strlen(schedstr))) {
        prof_on = SCHED_PROFILING;
        if (str[strlen(schedstr)] == ',')
            str += strlen(schedstr) + 1;
        if (get_option(&str, &par))
            prof_shift = par;
        printk(KERN_INFO
            "kernel schedule profiling enabled (shift: %ld)\n",
            prof_shift);
    } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
        prof_on = KVM_PROFILING;
        if (str[strlen(kvmstr)] == ',')
            str += strlen(kvmstr) + 1;
        if (get_option(&str, &par))
            prof_shift = par;
        printk(KERN_INFO
            "kernel KVM profiling enabled (shift: %ld)\n",
            prof_shift);
    } else if (get_option(&str, &par)) {
        prof_shift = par;
        prof_on = CPU_PROFILING;
        printk(KERN_INFO "kernel profiling enabled (shift: %ld)\n",
            prof_shift);
    }
    return 1;
}
__setup("profile=", profile_setup);


int __ref profile_init(void)
{
    int buffer_bytes;
    if (!prof_on)
        return 0;

    /* only text is profiled */
    prof_len = (_etext - _stext) >> prof_shift;
    buffer_bytes = prof_len*sizeof(atomic_t);

    if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
        return -ENOMEM;

    cpumask_copy(prof_cpu_mask, cpu_possible_mask);

    prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
    if (prof_buffer)
        return 0;

    prof_buffer = alloc_pages_exact(buffer_bytes,
                    GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
    if (prof_buffer)
        return 0;

    prof_buffer = vzalloc(buffer_bytes);
    if (prof_buffer)
        return 0;

    free_cpumask_var(prof_cpu_mask);
    return -ENOMEM;
}

/* Profile event notifications */

static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
static BLOCKING_NOTIFIER_HEAD(munmap_notifier);

void profile_task_exit(struct task_struct *task)
{
    blocking_notifier_call_chain(&task_exit_notifier, 0, task);
}

int profile_handoff_task(struct task_struct *task)
{
    int ret;
    ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
    return (ret == NOTIFY_OK) ? 1 : 0;
}

void profile_munmap(unsigned long addr)
{
    blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
}

int task_handoff_register(struct notifier_block *n)
{
    return atomic_notifier_chain_register(&task_free_notifier, n);
}
EXPORT_SYMBOL_GPL(task_handoff_register);

int task_handoff_unregister(struct notifier_block *n)
{
    return atomic_notifier_chain_unregister(&task_free_notifier, n);
}
EXPORT_SYMBOL_GPL(task_handoff_unregister);

int profile_event_register(enum profile_type type, struct notifier_block *n)
{
    int err = -EINVAL;

    switch (type) {
    case PROFILE_TASK_EXIT:
        err = blocking_notifier_chain_register(
                &task_exit_notifier, n);
        break;
    case PROFILE_MUNMAP:
        err = blocking_notifier_chain_register(
                &munmap_notifier, n);
        break;
    }

    return err;
}
EXPORT_SYMBOL_GPL(profile_event_register);

int profile_event_unregister(enum profile_type type, struct notifier_block *n)
{
    int err = -EINVAL;

    switch (type) {
    case PROFILE_TASK_EXIT:
        err = blocking_notifier_chain_unregister(
                &task_exit_notifier, n);
        break;
    case PROFILE_MUNMAP:
        err = blocking_notifier_chain_unregister(
                &munmap_notifier, n);
        break;
    }

    return err;
}
EXPORT_SYMBOL_GPL(profile_event_unregister);

int register_timer_hook(int (*hook)(struct pt_regs *))
{
    if (timer_hook)
        return -EBUSY;
    timer_hook = hook;
    return 0;
}
EXPORT_SYMBOL_GPL(register_timer_hook);

void unregister_timer_hook(int (*hook)(struct pt_regs *))
{
    WARN_ON(hook != timer_hook);
    timer_hook = NULL;
    /* make sure all CPUs see the NULL hook */
    synchronize_sched();  /* Allow ongoing interrupts to complete. */
}
EXPORT_SYMBOL_GPL(unregister_timer_hook);


#ifdef CONFIG_SMP
/*
 * Each cpu has a pair of open-addressed hashtables for pending
 * profile hits. read_profile() IPI's all cpus to request them
 * to flip buffers and flushes their contents to prof_buffer itself.
 * Flip requests are serialized by the profile_flip_mutex. The sole
 * use of having a second hashtable is for avoiding cacheline
 * contention that would otherwise happen during flushes of pending
 * profile hits required for the accuracy of reported profile hits
 * and so resurrect the interrupt livelock issue.
 *
 * The open-addressed hashtables are indexed by profile buffer slot
 * and hold the number of pending hits to that profile buffer slot on
 * a cpu in an entry. When the hashtable overflows, all pending hits
 * are accounted to their corresponding profile buffer slots with
 * atomic_add() and the hashtable emptied. As numerous pending hits
 * may be accounted to a profile buffer slot in a hashtable entry,
 * this amortizes a number of atomic profile buffer increments likely
 * to be far larger than the number of entries in the hashtable,
 * particularly given that the number of distinct profile buffer
 * positions to which hits are accounted during short intervals (e.g.
 * several seconds) is usually very small. Exclusion from buffer
 * flipping is provided by interrupt disablement (note that for
 * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
 * process context).
 * The hash function is meant to be lightweight as opposed to strong,
 * and was vaguely inspired by ppc64 firmware-supported inverted
 * pagetable hash functions, but uses a full hashtable full of finite
 * collision chains, not just pairs of them.
 *
 * -- wli
 */
static void __profile_flip_buffers(void *unused)
{
    int cpu = smp_processor_id();

    per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
}

static void profile_flip_buffers(void)
{
    int i, j, cpu;

    mutex_lock(&profile_flip_mutex);
    j = per_cpu(cpu_profile_flip, get_cpu());
    put_cpu();
    on_each_cpu(__profile_flip_buffers, NULL, 1);
    for_each_online_cpu(cpu) {
        struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
        for (i = 0; i < NR_PROFILE_HIT; ++i) {
            if (!hits[i].hits) {
                if (hits[i].pc)
                    hits[i].pc = 0;
                continue;
            }
            atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
            hits[i].hits = hits[i].pc = 0;
        }
    }
    mutex_unlock(&profile_flip_mutex);
}

static void profile_discard_flip_buffers(void)
{
    int i, cpu;

    mutex_lock(&profile_flip_mutex);
    i = per_cpu(cpu_profile_flip, get_cpu());
    put_cpu();
    on_each_cpu(__profile_flip_buffers, NULL, 1);
    for_each_online_cpu(cpu) {
        struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
        memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
    }
    mutex_unlock(&profile_flip_mutex);
}

static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
{
    unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
    int i, j, cpu;
    struct profile_hit *hits;

    pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
    i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
    secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
    cpu = get_cpu();
    hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
    if (!hits) {
        put_cpu();
        return;
    }
    /*
     * We buffer the global profiler buffer into a per-CPU
     * queue and thus reduce the number of global (and possibly
     * NUMA-alien) accesses. The write-queue is self-coalescing:
     */
    local_irq_save(flags);
    do {
        for (j = 0; j < PROFILE_GRPSZ; ++j) {
            if (hits[i + j].pc == pc) {
                hits[i + j].hits += nr_hits;
                goto out;
            } else if (!hits[i + j].hits) {
                hits[i + j].pc = pc;
                hits[i + j].hits = nr_hits;
                goto out;
            }
        }
        i = (i + secondary) & (NR_PROFILE_HIT - 1);
    } while (i != primary);

    /*
     * Add the current hit(s) and flush the write-queue out
     * to the global buffer:
     */
    atomic_add(nr_hits, &prof_buffer[pc]);
    for (i = 0; i < NR_PROFILE_HIT; ++i) {
        atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
        hits[i].pc = hits[i].hits = 0;
    }
out:
    local_irq_restore(flags);
    put_cpu();
}

static int __cpuinit profile_cpu_callback(struct notifier_block *info,
                    unsigned long action, void *__cpu)
{
    int node, cpu = (unsigned long)__cpu;
    struct page *page;

    switch (action) {
    case CPU_UP_PREPARE:
    case CPU_UP_PREPARE_FROZEN:
        node = cpu_to_mem(cpu);
        per_cpu(cpu_profile_flip, cpu) = 0;
        if (!per_cpu(cpu_profile_hits, cpu)[1]) {
            page = alloc_pages_exact_node(node,
                    GFP_KERNEL | __GFP_ZERO,
                    0);
            if (!page)
                return notifier_from_errno(-ENOMEM);
            per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
        }
        if (!per_cpu(cpu_profile_hits, cpu)[0]) {
            page = alloc_pages_exact_node(node,
                    GFP_KERNEL | __GFP_ZERO,
                    0);
            if (!page)
                goto out_free;
            per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
        }
        break;
out_free:
        page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
        per_cpu(cpu_profile_hits, cpu)[1] = NULL;
        __free_page(page);
        return notifier_from_errno(-ENOMEM);
    case CPU_ONLINE:
    case CPU_ONLINE_FROZEN:
        if (prof_cpu_mask != NULL)
            cpumask_set_cpu(cpu, prof_cpu_mask);
        break;
    case CPU_UP_CANCELED:
    case CPU_UP_CANCELED_FROZEN:
    case CPU_DEAD:
    case CPU_DEAD_FROZEN:
        if (prof_cpu_mask != NULL)
            cpumask_clear_cpu(cpu, prof_cpu_mask);
        if (per_cpu(cpu_profile_hits, cpu)[0]) {
            page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
            per_cpu(cpu_profile_hits, cpu)[0] = NULL;
            __free_page(page);
        }
        if (per_cpu(cpu_profile_hits, cpu)[1]) {
            page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
            per_cpu(cpu_profile_hits, cpu)[1] = NULL;
            __free_page(page);
        }
        break;
    }
    return NOTIFY_OK;
}
#else /* !CONFIG_SMP */
#define profile_flip_buffers()      do { } while (0)
#define profile_discard_flip_buffers()  do { } while (0)
#define profile_cpu_callback        NULL

static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
{
    unsigned long pc;
    pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
    atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
}
#endif /* !CONFIG_SMP */

void profile_hits(int type, void *__pc, unsigned int nr_hits)
{
    if (prof_on != type || !prof_buffer)
        return;
    do_profile_hits(type, __pc, nr_hits);
}
EXPORT_SYMBOL_GPL(profile_hits);

void profile_tick(int type)
{
    struct pt_regs *regs = get_irq_regs();

    if (type == CPU_PROFILING && timer_hook)
        timer_hook(regs);
    if (!user_mode(regs) && prof_cpu_mask != NULL &&
        cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
        profile_hit(type, (void *)profile_pc(regs));
}

#ifdef CONFIG_PROC_FS
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <asm/uaccess.h>

static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
{
    seq_cpumask(m, prof_cpu_mask);
    seq_putc(m, '\n');
    return 0;
}

static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
{
    return single_open(file, prof_cpu_mask_proc_show, NULL);
}

static ssize_t prof_cpu_mask_proc_write(struct file *file,
    const char __user *buffer, size_t count, loff_t *pos)
{
    cpumask_var_t new_value;
    int err;

    if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
        return -ENOMEM;

    err = cpumask_parse_user(buffer, count, new_value);
    if (!err) {
        cpumask_copy(prof_cpu_mask, new_value);
        err = count;
    }
    free_cpumask_var(new_value);
    return err;
}

static const struct file_operations prof_cpu_mask_proc_fops = {
    .open       = prof_cpu_mask_proc_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = single_release,
    .write      = prof_cpu_mask_proc_write,
};

void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir)
{
    /* create /proc/irq/prof_cpu_mask */
    proc_create("prof_cpu_mask", 0600, root_irq_dir, &prof_cpu_mask_proc_fops);
}

/*
 * This function accesses profiling information. The returned data is
 * binary: the sampling step and the actual contents of the profile
 * buffer. Use of the program readprofile is recommended in order to
 * get meaningful info out of these data.
 */
static ssize_t
read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
    unsigned long p = *ppos;
    ssize_t read;
    char *pnt;
    unsigned int sample_step = 1 << prof_shift;

    profile_flip_buffers();
    if (p >= (prof_len+1)*sizeof(unsigned int))
        return 0;
    if (count > (prof_len+1)*sizeof(unsigned int) - p)
        count = (prof_len+1)*sizeof(unsigned int) - p;
    read = 0;

    while (p < sizeof(unsigned int) && count > 0) {
        if (put_user(*((char *)(&sample_step)+p), buf))
            return -EFAULT;
        buf++; p++; count--; read++;
    }
    pnt = (char *)prof_buffer + p - sizeof(atomic_t);
    if (copy_to_user(buf, (void *)pnt, count))
        return -EFAULT;
    read += count;
    *ppos += read;
    return read;
}

/*
 * Writing to /proc/profile resets the counters
 *
 * Writing a 'profiling multiplier' value into it also re-sets the profiling
 * interrupt frequency, on architectures that support this.
 */
static ssize_t write_profile(struct file *file, const char __user *buf,
                 size_t count, loff_t *ppos)
{
#ifdef CONFIG_SMP
    extern int setup_profiling_timer(unsigned int multiplier);

    if (count == sizeof(int)) {
        unsigned int multiplier;

        if (copy_from_user(&multiplier, buf, sizeof(int)))
            return -EFAULT;

        if (setup_profiling_timer(multiplier))
            return -EINVAL;
    }
#endif
    profile_discard_flip_buffers();
    memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
    return count;
}

static const struct file_operations proc_profile_operations = {
    .read       = read_profile,
    .write      = write_profile,
    .llseek     = default_llseek,
};

#ifdef CONFIG_SMP
static void profile_nop(void *unused)
{
}

static int create_hash_tables(void)
{
    int cpu;

    for_each_online_cpu(cpu) {
        int node = cpu_to_mem(cpu);
        struct page *page;

        page = alloc_pages_exact_node(node,
                GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
                0);
        if (!page)
            goto out_cleanup;
        per_cpu(cpu_profile_hits, cpu)[1]
                = (struct profile_hit *)page_address(page);
        page = alloc_pages_exact_node(node,
                GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
                0);
        if (!page)
            goto out_cleanup;
        per_cpu(cpu_profile_hits, cpu)[0]
                = (struct profile_hit *)page_address(page);
    }
    return 0;
out_cleanup:
    prof_on = 0;
    smp_mb();
    on_each_cpu(profile_nop, NULL, 1);
    for_each_online_cpu(cpu) {
        struct page *page;

        if (per_cpu(cpu_profile_hits, cpu)[0]) {
            page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
            per_cpu(cpu_profile_hits, cpu)[0] = NULL;
            __free_page(page);
        }
        if (per_cpu(cpu_profile_hits, cpu)[1]) {
            page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
            per_cpu(cpu_profile_hits, cpu)[1] = NULL;
            __free_page(page);
        }
    }
    return -1;
}
#else
#define create_hash_tables()            ({ 0; })
#endif

int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */
{
    struct proc_dir_entry *entry;

    if (!prof_on)
        return 0;
    if (create_hash_tables())
        return -ENOMEM;
    entry = proc_create("profile", S_IWUSR | S_IRUGO,
                NULL, &proc_profile_operations);
    if (!entry)
        return 0;
    entry->size = (1+prof_len) * sizeof(atomic_t);
    hotcpu_notifier(profile_cpu_callback, 0);
    return 0;
}
module_init(create_proc_profile);
#endif /* CONFIG_PROC_FS */