Root/kernel/profile.c

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 * William Irwin, Oracle, July 2004
12 * Amortized hit count accounting via per-cpu open-addressed hashtables
13 * to resolve timer interrupt livelocks, William Irwin, Oracle, 2004
14 */
15
16#include <linux/export.h>
17#include <linux/profile.h>
18#include <linux/bootmem.h>
19#include <linux/notifier.h>
20#include <linux/mm.h>
21#include <linux/cpumask.h>
22#include <linux/cpu.h>
23#include <linux/highmem.h>
24#include <linux/mutex.h>
25#include <linux/slab.h>
26#include <linux/vmalloc.h>
27#include <asm/sections.h>
28#include <asm/irq_regs.h>
29#include <asm/ptrace.h>
30
31struct profile_hit {
32    u32 pc, hits;
33};
34#define PROFILE_GRPSHIFT 3
35#define PROFILE_GRPSZ (1 << PROFILE_GRPSHIFT)
36#define NR_PROFILE_HIT (PAGE_SIZE/sizeof(struct profile_hit))
37#define NR_PROFILE_GRP (NR_PROFILE_HIT/PROFILE_GRPSZ)
38
39/* Oprofile timer tick hook */
40static int (*timer_hook)(struct pt_regs *) __read_mostly;
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#ifdef CONFIG_SMP
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 char schedstr[] = "schedule";
58    static char sleepstr[] = "sleep";
59    static char kvmstr[] = "kvm";
60    int par;
61
62    if (!strncmp(str, sleepstr, strlen(sleepstr))) {
63#ifdef CONFIG_SCHEDSTATS
64        prof_on = SLEEP_PROFILING;
65        if (str[strlen(sleepstr)] == ',')
66            str += strlen(sleepstr) + 1;
67        if (get_option(&str, &par))
68            prof_shift = par;
69        printk(KERN_INFO
70            "kernel sleep profiling enabled (shift: %ld)\n",
71            prof_shift);
72#else
73        printk(KERN_WARNING
74            "kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
75#endif /* CONFIG_SCHEDSTATS */
76    } else if (!strncmp(str, schedstr, strlen(schedstr))) {
77        prof_on = SCHED_PROFILING;
78        if (str[strlen(schedstr)] == ',')
79            str += strlen(schedstr) + 1;
80        if (get_option(&str, &par))
81            prof_shift = par;
82        printk(KERN_INFO
83            "kernel schedule profiling enabled (shift: %ld)\n",
84            prof_shift);
85    } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
86        prof_on = KVM_PROFILING;
87        if (str[strlen(kvmstr)] == ',')
88            str += strlen(kvmstr) + 1;
89        if (get_option(&str, &par))
90            prof_shift = par;
91        printk(KERN_INFO
92            "kernel KVM profiling enabled (shift: %ld)\n",
93            prof_shift);
94    } else if (get_option(&str, &par)) {
95        prof_shift = par;
96        prof_on = CPU_PROFILING;
97        printk(KERN_INFO "kernel profiling enabled (shift: %ld)\n",
98            prof_shift);
99    }
100    return 1;
101}
102__setup("profile=", profile_setup);
103
104
105int __ref profile_init(void)
106{
107    int buffer_bytes;
108    if (!prof_on)
109        return 0;
110
111    /* only text is profiled */
112    prof_len = (_etext - _stext) >> prof_shift;
113    buffer_bytes = prof_len*sizeof(atomic_t);
114
115    if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
116        return -ENOMEM;
117
118    cpumask_copy(prof_cpu_mask, cpu_possible_mask);
119
120    prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
121    if (prof_buffer)
122        return 0;
123
124    prof_buffer = alloc_pages_exact(buffer_bytes,
125                    GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
126    if (prof_buffer)
127        return 0;
128
129    prof_buffer = vzalloc(buffer_bytes);
130    if (prof_buffer)
131        return 0;
132
133    free_cpumask_var(prof_cpu_mask);
134    return -ENOMEM;
135}
136
137/* Profile event notifications */
138
139static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
140static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
141static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
142
143void profile_task_exit(struct task_struct *task)
144{
145    blocking_notifier_call_chain(&task_exit_notifier, 0, task);
146}
147
148int profile_handoff_task(struct task_struct *task)
149{
150    int ret;
151    ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
152    return (ret == NOTIFY_OK) ? 1 : 0;
153}
154
155void profile_munmap(unsigned long addr)
156{
157    blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
158}
159
160int task_handoff_register(struct notifier_block *n)
161{
162    return atomic_notifier_chain_register(&task_free_notifier, n);
163}
164EXPORT_SYMBOL_GPL(task_handoff_register);
165
166int task_handoff_unregister(struct notifier_block *n)
167{
168    return atomic_notifier_chain_unregister(&task_free_notifier, n);
169}
170EXPORT_SYMBOL_GPL(task_handoff_unregister);
171
172int profile_event_register(enum profile_type type, struct notifier_block *n)
173{
174    int err = -EINVAL;
175
176    switch (type) {
177    case PROFILE_TASK_EXIT:
178        err = blocking_notifier_chain_register(
179                &task_exit_notifier, n);
180        break;
181    case PROFILE_MUNMAP:
182        err = blocking_notifier_chain_register(
183                &munmap_notifier, n);
184        break;
185    }
186
187    return err;
188}
189EXPORT_SYMBOL_GPL(profile_event_register);
190
191int profile_event_unregister(enum profile_type type, struct notifier_block *n)
192{
193    int err = -EINVAL;
194
195    switch (type) {
196    case PROFILE_TASK_EXIT:
197        err = blocking_notifier_chain_unregister(
198                &task_exit_notifier, n);
199        break;
200    case PROFILE_MUNMAP:
201        err = blocking_notifier_chain_unregister(
202                &munmap_notifier, n);
203        break;
204    }
205
206    return err;
207}
208EXPORT_SYMBOL_GPL(profile_event_unregister);
209
210int register_timer_hook(int (*hook)(struct pt_regs *))
211{
212    if (timer_hook)
213        return -EBUSY;
214    timer_hook = hook;
215    return 0;
216}
217EXPORT_SYMBOL_GPL(register_timer_hook);
218
219void unregister_timer_hook(int (*hook)(struct pt_regs *))
220{
221    WARN_ON(hook != timer_hook);
222    timer_hook = NULL;
223    /* make sure all CPUs see the NULL hook */
224    synchronize_sched(); /* Allow ongoing interrupts to complete. */
225}
226EXPORT_SYMBOL_GPL(unregister_timer_hook);
227
228
229#ifdef CONFIG_SMP
230/*
231 * Each cpu has a pair of open-addressed hashtables for pending
232 * profile hits. read_profile() IPI's all cpus to request them
233 * to flip buffers and flushes their contents to prof_buffer itself.
234 * Flip requests are serialized by the profile_flip_mutex. The sole
235 * use of having a second hashtable is for avoiding cacheline
236 * contention that would otherwise happen during flushes of pending
237 * profile hits required for the accuracy of reported profile hits
238 * and so resurrect the interrupt livelock issue.
239 *
240 * The open-addressed hashtables are indexed by profile buffer slot
241 * and hold the number of pending hits to that profile buffer slot on
242 * a cpu in an entry. When the hashtable overflows, all pending hits
243 * are accounted to their corresponding profile buffer slots with
244 * atomic_add() and the hashtable emptied. As numerous pending hits
245 * may be accounted to a profile buffer slot in a hashtable entry,
246 * this amortizes a number of atomic profile buffer increments likely
247 * to be far larger than the number of entries in the hashtable,
248 * particularly given that the number of distinct profile buffer
249 * positions to which hits are accounted during short intervals (e.g.
250 * several seconds) is usually very small. Exclusion from buffer
251 * flipping is provided by interrupt disablement (note that for
252 * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
253 * process context).
254 * The hash function is meant to be lightweight as opposed to strong,
255 * and was vaguely inspired by ppc64 firmware-supported inverted
256 * pagetable hash functions, but uses a full hashtable full of finite
257 * collision chains, not just pairs of them.
258 *
259 * -- wli
260 */
261static void __profile_flip_buffers(void *unused)
262{
263    int cpu = smp_processor_id();
264
265    per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
266}
267
268static void profile_flip_buffers(void)
269{
270    int i, j, cpu;
271
272    mutex_lock(&profile_flip_mutex);
273    j = per_cpu(cpu_profile_flip, get_cpu());
274    put_cpu();
275    on_each_cpu(__profile_flip_buffers, NULL, 1);
276    for_each_online_cpu(cpu) {
277        struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
278        for (i = 0; i < NR_PROFILE_HIT; ++i) {
279            if (!hits[i].hits) {
280                if (hits[i].pc)
281                    hits[i].pc = 0;
282                continue;
283            }
284            atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
285            hits[i].hits = hits[i].pc = 0;
286        }
287    }
288    mutex_unlock(&profile_flip_mutex);
289}
290
291static void profile_discard_flip_buffers(void)
292{
293    int i, cpu;
294
295    mutex_lock(&profile_flip_mutex);
296    i = per_cpu(cpu_profile_flip, get_cpu());
297    put_cpu();
298    on_each_cpu(__profile_flip_buffers, NULL, 1);
299    for_each_online_cpu(cpu) {
300        struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
301        memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
302    }
303    mutex_unlock(&profile_flip_mutex);
304}
305
306static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
307{
308    unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
309    int i, j, cpu;
310    struct profile_hit *hits;
311
312    pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
313    i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
314    secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
315    cpu = get_cpu();
316    hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
317    if (!hits) {
318        put_cpu();
319        return;
320    }
321    /*
322     * We buffer the global profiler buffer into a per-CPU
323     * queue and thus reduce the number of global (and possibly
324     * NUMA-alien) accesses. The write-queue is self-coalescing:
325     */
326    local_irq_save(flags);
327    do {
328        for (j = 0; j < PROFILE_GRPSZ; ++j) {
329            if (hits[i + j].pc == pc) {
330                hits[i + j].hits += nr_hits;
331                goto out;
332            } else if (!hits[i + j].hits) {
333                hits[i + j].pc = pc;
334                hits[i + j].hits = nr_hits;
335                goto out;
336            }
337        }
338        i = (i + secondary) & (NR_PROFILE_HIT - 1);
339    } while (i != primary);
340
341    /*
342     * Add the current hit(s) and flush the write-queue out
343     * to the global buffer:
344     */
345    atomic_add(nr_hits, &prof_buffer[pc]);
346    for (i = 0; i < NR_PROFILE_HIT; ++i) {
347        atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
348        hits[i].pc = hits[i].hits = 0;
349    }
350out:
351    local_irq_restore(flags);
352    put_cpu();
353}
354
355static int __cpuinit profile_cpu_callback(struct notifier_block *info,
356                    unsigned long action, void *__cpu)
357{
358    int node, cpu = (unsigned long)__cpu;
359    struct page *page;
360
361    switch (action) {
362    case CPU_UP_PREPARE:
363    case CPU_UP_PREPARE_FROZEN:
364        node = cpu_to_mem(cpu);
365        per_cpu(cpu_profile_flip, cpu) = 0;
366        if (!per_cpu(cpu_profile_hits, cpu)[1]) {
367            page = alloc_pages_exact_node(node,
368                    GFP_KERNEL | __GFP_ZERO,
369                    0);
370            if (!page)
371                return notifier_from_errno(-ENOMEM);
372            per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
373        }
374        if (!per_cpu(cpu_profile_hits, cpu)[0]) {
375            page = alloc_pages_exact_node(node,
376                    GFP_KERNEL | __GFP_ZERO,
377                    0);
378            if (!page)
379                goto out_free;
380            per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
381        }
382        break;
383out_free:
384        page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
385        per_cpu(cpu_profile_hits, cpu)[1] = NULL;
386        __free_page(page);
387        return notifier_from_errno(-ENOMEM);
388    case CPU_ONLINE:
389    case CPU_ONLINE_FROZEN:
390        if (prof_cpu_mask != NULL)
391            cpumask_set_cpu(cpu, prof_cpu_mask);
392        break;
393    case CPU_UP_CANCELED:
394    case CPU_UP_CANCELED_FROZEN:
395    case CPU_DEAD:
396    case CPU_DEAD_FROZEN:
397        if (prof_cpu_mask != NULL)
398            cpumask_clear_cpu(cpu, prof_cpu_mask);
399        if (per_cpu(cpu_profile_hits, cpu)[0]) {
400            page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
401            per_cpu(cpu_profile_hits, cpu)[0] = NULL;
402            __free_page(page);
403        }
404        if (per_cpu(cpu_profile_hits, cpu)[1]) {
405            page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
406            per_cpu(cpu_profile_hits, cpu)[1] = NULL;
407            __free_page(page);
408        }
409        break;
410    }
411    return NOTIFY_OK;
412}
413#else /* !CONFIG_SMP */
414#define profile_flip_buffers() do { } while (0)
415#define profile_discard_flip_buffers() do { } while (0)
416#define profile_cpu_callback NULL
417
418static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
419{
420    unsigned long pc;
421    pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
422    atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
423}
424#endif /* !CONFIG_SMP */
425
426void profile_hits(int type, void *__pc, unsigned int nr_hits)
427{
428    if (prof_on != type || !prof_buffer)
429        return;
430    do_profile_hits(type, __pc, nr_hits);
431}
432EXPORT_SYMBOL_GPL(profile_hits);
433
434void profile_tick(int type)
435{
436    struct pt_regs *regs = get_irq_regs();
437
438    if (type == CPU_PROFILING && timer_hook)
439        timer_hook(regs);
440    if (!user_mode(regs) && prof_cpu_mask != NULL &&
441        cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
442        profile_hit(type, (void *)profile_pc(regs));
443}
444
445#ifdef CONFIG_PROC_FS
446#include <linux/proc_fs.h>
447#include <linux/seq_file.h>
448#include <asm/uaccess.h>
449
450static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
451{
452    seq_cpumask(m, prof_cpu_mask);
453    seq_putc(m, '\n');
454    return 0;
455}
456
457static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
458{
459    return single_open(file, prof_cpu_mask_proc_show, NULL);
460}
461
462static ssize_t prof_cpu_mask_proc_write(struct file *file,
463    const char __user *buffer, size_t count, loff_t *pos)
464{
465    cpumask_var_t new_value;
466    int err;
467
468    if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
469        return -ENOMEM;
470
471    err = cpumask_parse_user(buffer, count, new_value);
472    if (!err) {
473        cpumask_copy(prof_cpu_mask, new_value);
474        err = count;
475    }
476    free_cpumask_var(new_value);
477    return err;
478}
479
480static const struct file_operations prof_cpu_mask_proc_fops = {
481    .open = prof_cpu_mask_proc_open,
482    .read = seq_read,
483    .llseek = seq_lseek,
484    .release = single_release,
485    .write = prof_cpu_mask_proc_write,
486};
487
488void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir)
489{
490    /* create /proc/irq/prof_cpu_mask */
491    proc_create("prof_cpu_mask", 0600, root_irq_dir, &prof_cpu_mask_proc_fops);
492}
493
494/*
495 * This function accesses profiling information. The returned data is
496 * binary: the sampling step and the actual contents of the profile
497 * buffer. Use of the program readprofile is recommended in order to
498 * get meaningful info out of these data.
499 */
500static ssize_t
501read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
502{
503    unsigned long p = *ppos;
504    ssize_t read;
505    char *pnt;
506    unsigned int sample_step = 1 << prof_shift;
507
508    profile_flip_buffers();
509    if (p >= (prof_len+1)*sizeof(unsigned int))
510        return 0;
511    if (count > (prof_len+1)*sizeof(unsigned int) - p)
512        count = (prof_len+1)*sizeof(unsigned int) - p;
513    read = 0;
514
515    while (p < sizeof(unsigned int) && count > 0) {
516        if (put_user(*((char *)(&sample_step)+p), buf))
517            return -EFAULT;
518        buf++; p++; count--; read++;
519    }
520    pnt = (char *)prof_buffer + p - sizeof(atomic_t);
521    if (copy_to_user(buf, (void *)pnt, count))
522        return -EFAULT;
523    read += count;
524    *ppos += read;
525    return read;
526}
527
528/*
529 * Writing to /proc/profile resets the counters
530 *
531 * Writing a 'profiling multiplier' value into it also re-sets the profiling
532 * interrupt frequency, on architectures that support this.
533 */
534static ssize_t write_profile(struct file *file, const char __user *buf,
535                 size_t count, loff_t *ppos)
536{
537#ifdef CONFIG_SMP
538    extern int setup_profiling_timer(unsigned int multiplier);
539
540    if (count == sizeof(int)) {
541        unsigned int multiplier;
542
543        if (copy_from_user(&multiplier, buf, sizeof(int)))
544            return -EFAULT;
545
546        if (setup_profiling_timer(multiplier))
547            return -EINVAL;
548    }
549#endif
550    profile_discard_flip_buffers();
551    memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
552    return count;
553}
554
555static const struct file_operations proc_profile_operations = {
556    .read = read_profile,
557    .write = write_profile,
558    .llseek = default_llseek,
559};
560
561#ifdef CONFIG_SMP
562static void profile_nop(void *unused)
563{
564}
565
566static int create_hash_tables(void)
567{
568    int cpu;
569
570    for_each_online_cpu(cpu) {
571        int node = cpu_to_mem(cpu);
572        struct page *page;
573
574        page = alloc_pages_exact_node(node,
575                GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
576                0);
577        if (!page)
578            goto out_cleanup;
579        per_cpu(cpu_profile_hits, cpu)[1]
580                = (struct profile_hit *)page_address(page);
581        page = alloc_pages_exact_node(node,
582                GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
583                0);
584        if (!page)
585            goto out_cleanup;
586        per_cpu(cpu_profile_hits, cpu)[0]
587                = (struct profile_hit *)page_address(page);
588    }
589    return 0;
590out_cleanup:
591    prof_on = 0;
592    smp_mb();
593    on_each_cpu(profile_nop, NULL, 1);
594    for_each_online_cpu(cpu) {
595        struct page *page;
596
597        if (per_cpu(cpu_profile_hits, cpu)[0]) {
598            page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
599            per_cpu(cpu_profile_hits, cpu)[0] = NULL;
600            __free_page(page);
601        }
602        if (per_cpu(cpu_profile_hits, cpu)[1]) {
603            page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
604            per_cpu(cpu_profile_hits, cpu)[1] = NULL;
605            __free_page(page);
606        }
607    }
608    return -1;
609}
610#else
611#define create_hash_tables() ({ 0; })
612#endif
613
614int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */
615{
616    struct proc_dir_entry *entry;
617
618    if (!prof_on)
619        return 0;
620    if (create_hash_tables())
621        return -ENOMEM;
622    entry = proc_create("profile", S_IWUSR | S_IRUGO,
623                NULL, &proc_profile_operations);
624    if (!entry)
625        return 0;
626    entry->size = (1+prof_len) * sizeof(atomic_t);
627    hotcpu_notifier(profile_cpu_callback, 0);
628    return 0;
629}
630module_init(create_proc_profile);
631#endif /* CONFIG_PROC_FS */
632

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