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 * 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/bootmem.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 <asm/sections.h>
29#include <asm/irq_regs.h>
30#include <asm/ptrace.h>
31
32struct profile_hit {
33    u32 pc, hits;
34};
35#define PROFILE_GRPSHIFT 3
36#define PROFILE_GRPSZ (1 << PROFILE_GRPSHIFT)
37#define NR_PROFILE_HIT (PAGE_SIZE/sizeof(struct profile_hit))
38#define NR_PROFILE_GRP (NR_PROFILE_HIT/PROFILE_GRPSZ)
39
40static atomic_t *prof_buffer;
41static unsigned long prof_len, prof_shift;
42
43int prof_on __read_mostly;
44EXPORT_SYMBOL_GPL(prof_on);
45
46static cpumask_var_t prof_cpu_mask;
47#ifdef CONFIG_SMP
48static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
49static DEFINE_PER_CPU(int, cpu_profile_flip);
50static DEFINE_MUTEX(profile_flip_mutex);
51#endif /* CONFIG_SMP */
52
53int profile_setup(char *str)
54{
55    static char schedstr[] = "schedule";
56    static char sleepstr[] = "sleep";
57    static char kvmstr[] = "kvm";
58    int par;
59
60    if (!strncmp(str, sleepstr, strlen(sleepstr))) {
61#ifdef CONFIG_SCHEDSTATS
62        prof_on = SLEEP_PROFILING;
63        if (str[strlen(sleepstr)] == ',')
64            str += strlen(sleepstr) + 1;
65        if (get_option(&str, &par))
66            prof_shift = par;
67        printk(KERN_INFO
68            "kernel sleep profiling enabled (shift: %ld)\n",
69            prof_shift);
70#else
71        printk(KERN_WARNING
72            "kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
73#endif /* CONFIG_SCHEDSTATS */
74    } else if (!strncmp(str, schedstr, strlen(schedstr))) {
75        prof_on = SCHED_PROFILING;
76        if (str[strlen(schedstr)] == ',')
77            str += strlen(schedstr) + 1;
78        if (get_option(&str, &par))
79            prof_shift = par;
80        printk(KERN_INFO
81            "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        printk(KERN_INFO
90            "kernel KVM profiling enabled (shift: %ld)\n",
91            prof_shift);
92    } else if (get_option(&str, &par)) {
93        prof_shift = par;
94        prof_on = CPU_PROFILING;
95        printk(KERN_INFO "kernel profiling enabled (shift: %ld)\n",
96            prof_shift);
97    }
98    return 1;
99}
100__setup("profile=", profile_setup);
101
102
103int __ref profile_init(void)
104{
105    int buffer_bytes;
106    if (!prof_on)
107        return 0;
108
109    /* only text is profiled */
110    prof_len = (_etext - _stext) >> prof_shift;
111    buffer_bytes = prof_len*sizeof(atomic_t);
112
113    if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
114        return -ENOMEM;
115
116    cpumask_copy(prof_cpu_mask, cpu_possible_mask);
117
118    prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
119    if (prof_buffer)
120        return 0;
121
122    prof_buffer = alloc_pages_exact(buffer_bytes,
123                    GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
124    if (prof_buffer)
125        return 0;
126
127    prof_buffer = vzalloc(buffer_bytes);
128    if (prof_buffer)
129        return 0;
130
131    free_cpumask_var(prof_cpu_mask);
132    return -ENOMEM;
133}
134
135/* Profile event notifications */
136
137static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
138static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
139static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
140
141void profile_task_exit(struct task_struct *task)
142{
143    blocking_notifier_call_chain(&task_exit_notifier, 0, task);
144}
145
146int profile_handoff_task(struct task_struct *task)
147{
148    int ret;
149    ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
150    return (ret == NOTIFY_OK) ? 1 : 0;
151}
152
153void profile_munmap(unsigned long addr)
154{
155    blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
156}
157
158int task_handoff_register(struct notifier_block *n)
159{
160    return atomic_notifier_chain_register(&task_free_notifier, n);
161}
162EXPORT_SYMBOL_GPL(task_handoff_register);
163
164int task_handoff_unregister(struct notifier_block *n)
165{
166    return atomic_notifier_chain_unregister(&task_free_notifier, n);
167}
168EXPORT_SYMBOL_GPL(task_handoff_unregister);
169
170int profile_event_register(enum profile_type type, struct notifier_block *n)
171{
172    int err = -EINVAL;
173
174    switch (type) {
175    case PROFILE_TASK_EXIT:
176        err = blocking_notifier_chain_register(
177                &task_exit_notifier, n);
178        break;
179    case PROFILE_MUNMAP:
180        err = blocking_notifier_chain_register(
181                &munmap_notifier, n);
182        break;
183    }
184
185    return err;
186}
187EXPORT_SYMBOL_GPL(profile_event_register);
188
189int profile_event_unregister(enum profile_type type, struct notifier_block *n)
190{
191    int err = -EINVAL;
192
193    switch (type) {
194    case PROFILE_TASK_EXIT:
195        err = blocking_notifier_chain_unregister(
196                &task_exit_notifier, n);
197        break;
198    case PROFILE_MUNMAP:
199        err = blocking_notifier_chain_unregister(
200                &munmap_notifier, n);
201        break;
202    }
203
204    return err;
205}
206EXPORT_SYMBOL_GPL(profile_event_unregister);
207
208#ifdef CONFIG_SMP
209/*
210 * Each cpu has a pair of open-addressed hashtables for pending
211 * profile hits. read_profile() IPI's all cpus to request them
212 * to flip buffers and flushes their contents to prof_buffer itself.
213 * Flip requests are serialized by the profile_flip_mutex. The sole
214 * use of having a second hashtable is for avoiding cacheline
215 * contention that would otherwise happen during flushes of pending
216 * profile hits required for the accuracy of reported profile hits
217 * and so resurrect the interrupt livelock issue.
218 *
219 * The open-addressed hashtables are indexed by profile buffer slot
220 * and hold the number of pending hits to that profile buffer slot on
221 * a cpu in an entry. When the hashtable overflows, all pending hits
222 * are accounted to their corresponding profile buffer slots with
223 * atomic_add() and the hashtable emptied. As numerous pending hits
224 * may be accounted to a profile buffer slot in a hashtable entry,
225 * this amortizes a number of atomic profile buffer increments likely
226 * to be far larger than the number of entries in the hashtable,
227 * particularly given that the number of distinct profile buffer
228 * positions to which hits are accounted during short intervals (e.g.
229 * several seconds) is usually very small. Exclusion from buffer
230 * flipping is provided by interrupt disablement (note that for
231 * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
232 * process context).
233 * The hash function is meant to be lightweight as opposed to strong,
234 * and was vaguely inspired by ppc64 firmware-supported inverted
235 * pagetable hash functions, but uses a full hashtable full of finite
236 * collision chains, not just pairs of them.
237 *
238 * -- nyc
239 */
240static void __profile_flip_buffers(void *unused)
241{
242    int cpu = smp_processor_id();
243
244    per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
245}
246
247static void profile_flip_buffers(void)
248{
249    int i, j, cpu;
250
251    mutex_lock(&profile_flip_mutex);
252    j = per_cpu(cpu_profile_flip, get_cpu());
253    put_cpu();
254    on_each_cpu(__profile_flip_buffers, NULL, 1);
255    for_each_online_cpu(cpu) {
256        struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
257        for (i = 0; i < NR_PROFILE_HIT; ++i) {
258            if (!hits[i].hits) {
259                if (hits[i].pc)
260                    hits[i].pc = 0;
261                continue;
262            }
263            atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
264            hits[i].hits = hits[i].pc = 0;
265        }
266    }
267    mutex_unlock(&profile_flip_mutex);
268}
269
270static void profile_discard_flip_buffers(void)
271{
272    int i, cpu;
273
274    mutex_lock(&profile_flip_mutex);
275    i = per_cpu(cpu_profile_flip, get_cpu());
276    put_cpu();
277    on_each_cpu(__profile_flip_buffers, NULL, 1);
278    for_each_online_cpu(cpu) {
279        struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
280        memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
281    }
282    mutex_unlock(&profile_flip_mutex);
283}
284
285static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
286{
287    unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
288    int i, j, cpu;
289    struct profile_hit *hits;
290
291    pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
292    i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
293    secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
294    cpu = get_cpu();
295    hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
296    if (!hits) {
297        put_cpu();
298        return;
299    }
300    /*
301     * We buffer the global profiler buffer into a per-CPU
302     * queue and thus reduce the number of global (and possibly
303     * NUMA-alien) accesses. The write-queue is self-coalescing:
304     */
305    local_irq_save(flags);
306    do {
307        for (j = 0; j < PROFILE_GRPSZ; ++j) {
308            if (hits[i + j].pc == pc) {
309                hits[i + j].hits += nr_hits;
310                goto out;
311            } else if (!hits[i + j].hits) {
312                hits[i + j].pc = pc;
313                hits[i + j].hits = nr_hits;
314                goto out;
315            }
316        }
317        i = (i + secondary) & (NR_PROFILE_HIT - 1);
318    } while (i != primary);
319
320    /*
321     * Add the current hit(s) and flush the write-queue out
322     * to the global buffer:
323     */
324    atomic_add(nr_hits, &prof_buffer[pc]);
325    for (i = 0; i < NR_PROFILE_HIT; ++i) {
326        atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
327        hits[i].pc = hits[i].hits = 0;
328    }
329out:
330    local_irq_restore(flags);
331    put_cpu();
332}
333
334static int profile_cpu_callback(struct notifier_block *info,
335                    unsigned long action, void *__cpu)
336{
337    int node, cpu = (unsigned long)__cpu;
338    struct page *page;
339
340    switch (action) {
341    case CPU_UP_PREPARE:
342    case CPU_UP_PREPARE_FROZEN:
343        node = cpu_to_mem(cpu);
344        per_cpu(cpu_profile_flip, cpu) = 0;
345        if (!per_cpu(cpu_profile_hits, cpu)[1]) {
346            page = alloc_pages_exact_node(node,
347                    GFP_KERNEL | __GFP_ZERO,
348                    0);
349            if (!page)
350                return notifier_from_errno(-ENOMEM);
351            per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
352        }
353        if (!per_cpu(cpu_profile_hits, cpu)[0]) {
354            page = alloc_pages_exact_node(node,
355                    GFP_KERNEL | __GFP_ZERO,
356                    0);
357            if (!page)
358                goto out_free;
359            per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
360        }
361        break;
362out_free:
363        page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
364        per_cpu(cpu_profile_hits, cpu)[1] = NULL;
365        __free_page(page);
366        return notifier_from_errno(-ENOMEM);
367    case CPU_ONLINE:
368    case CPU_ONLINE_FROZEN:
369        if (prof_cpu_mask != NULL)
370            cpumask_set_cpu(cpu, prof_cpu_mask);
371        break;
372    case CPU_UP_CANCELED:
373    case CPU_UP_CANCELED_FROZEN:
374    case CPU_DEAD:
375    case CPU_DEAD_FROZEN:
376        if (prof_cpu_mask != NULL)
377            cpumask_clear_cpu(cpu, prof_cpu_mask);
378        if (per_cpu(cpu_profile_hits, cpu)[0]) {
379            page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
380            per_cpu(cpu_profile_hits, cpu)[0] = NULL;
381            __free_page(page);
382        }
383        if (per_cpu(cpu_profile_hits, cpu)[1]) {
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        }
388        break;
389    }
390    return NOTIFY_OK;
391}
392#else /* !CONFIG_SMP */
393#define profile_flip_buffers() do { } while (0)
394#define profile_discard_flip_buffers() do { } while (0)
395#define profile_cpu_callback NULL
396
397static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
398{
399    unsigned long pc;
400    pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
401    atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
402}
403#endif /* !CONFIG_SMP */
404
405void profile_hits(int type, void *__pc, unsigned int nr_hits)
406{
407    if (prof_on != type || !prof_buffer)
408        return;
409    do_profile_hits(type, __pc, nr_hits);
410}
411EXPORT_SYMBOL_GPL(profile_hits);
412
413void profile_tick(int type)
414{
415    struct pt_regs *regs = get_irq_regs();
416
417    if (!user_mode(regs) && prof_cpu_mask != NULL &&
418        cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
419        profile_hit(type, (void *)profile_pc(regs));
420}
421
422#ifdef CONFIG_PROC_FS
423#include <linux/proc_fs.h>
424#include <linux/seq_file.h>
425#include <asm/uaccess.h>
426
427static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
428{
429    seq_cpumask(m, prof_cpu_mask);
430    seq_putc(m, '\n');
431    return 0;
432}
433
434static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
435{
436    return single_open(file, prof_cpu_mask_proc_show, NULL);
437}
438
439static ssize_t prof_cpu_mask_proc_write(struct file *file,
440    const char __user *buffer, size_t count, loff_t *pos)
441{
442    cpumask_var_t new_value;
443    int err;
444
445    if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
446        return -ENOMEM;
447
448    err = cpumask_parse_user(buffer, count, new_value);
449    if (!err) {
450        cpumask_copy(prof_cpu_mask, new_value);
451        err = count;
452    }
453    free_cpumask_var(new_value);
454    return err;
455}
456
457static const struct file_operations prof_cpu_mask_proc_fops = {
458    .open = prof_cpu_mask_proc_open,
459    .read = seq_read,
460    .llseek = seq_lseek,
461    .release = single_release,
462    .write = prof_cpu_mask_proc_write,
463};
464
465void create_prof_cpu_mask(void)
466{
467    /* create /proc/irq/prof_cpu_mask */
468    proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_fops);
469}
470
471/*
472 * This function accesses profiling information. The returned data is
473 * binary: the sampling step and the actual contents of the profile
474 * buffer. Use of the program readprofile is recommended in order to
475 * get meaningful info out of these data.
476 */
477static ssize_t
478read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
479{
480    unsigned long p = *ppos;
481    ssize_t read;
482    char *pnt;
483    unsigned int sample_step = 1 << prof_shift;
484
485    profile_flip_buffers();
486    if (p >= (prof_len+1)*sizeof(unsigned int))
487        return 0;
488    if (count > (prof_len+1)*sizeof(unsigned int) - p)
489        count = (prof_len+1)*sizeof(unsigned int) - p;
490    read = 0;
491
492    while (p < sizeof(unsigned int) && count > 0) {
493        if (put_user(*((char *)(&sample_step)+p), buf))
494            return -EFAULT;
495        buf++; p++; count--; read++;
496    }
497    pnt = (char *)prof_buffer + p - sizeof(atomic_t);
498    if (copy_to_user(buf, (void *)pnt, count))
499        return -EFAULT;
500    read += count;
501    *ppos += read;
502    return read;
503}
504
505/*
506 * Writing to /proc/profile resets the counters
507 *
508 * Writing a 'profiling multiplier' value into it also re-sets the profiling
509 * interrupt frequency, on architectures that support this.
510 */
511static ssize_t write_profile(struct file *file, const char __user *buf,
512                 size_t count, loff_t *ppos)
513{
514#ifdef CONFIG_SMP
515    extern int setup_profiling_timer(unsigned int multiplier);
516
517    if (count == sizeof(int)) {
518        unsigned int multiplier;
519
520        if (copy_from_user(&multiplier, buf, sizeof(int)))
521            return -EFAULT;
522
523        if (setup_profiling_timer(multiplier))
524            return -EINVAL;
525    }
526#endif
527    profile_discard_flip_buffers();
528    memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
529    return count;
530}
531
532static const struct file_operations proc_profile_operations = {
533    .read = read_profile,
534    .write = write_profile,
535    .llseek = default_llseek,
536};
537
538#ifdef CONFIG_SMP
539static void profile_nop(void *unused)
540{
541}
542
543static int create_hash_tables(void)
544{
545    int cpu;
546
547    for_each_online_cpu(cpu) {
548        int node = cpu_to_mem(cpu);
549        struct page *page;
550
551        page = alloc_pages_exact_node(node,
552                GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
553                0);
554        if (!page)
555            goto out_cleanup;
556        per_cpu(cpu_profile_hits, cpu)[1]
557                = (struct profile_hit *)page_address(page);
558        page = alloc_pages_exact_node(node,
559                GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
560                0);
561        if (!page)
562            goto out_cleanup;
563        per_cpu(cpu_profile_hits, cpu)[0]
564                = (struct profile_hit *)page_address(page);
565    }
566    return 0;
567out_cleanup:
568    prof_on = 0;
569    smp_mb();
570    on_each_cpu(profile_nop, NULL, 1);
571    for_each_online_cpu(cpu) {
572        struct page *page;
573
574        if (per_cpu(cpu_profile_hits, cpu)[0]) {
575            page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
576            per_cpu(cpu_profile_hits, cpu)[0] = NULL;
577            __free_page(page);
578        }
579        if (per_cpu(cpu_profile_hits, cpu)[1]) {
580            page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
581            per_cpu(cpu_profile_hits, cpu)[1] = NULL;
582            __free_page(page);
583        }
584    }
585    return -1;
586}
587#else
588#define create_hash_tables() ({ 0; })
589#endif
590
591int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */
592{
593    struct proc_dir_entry *entry;
594    int err = 0;
595
596    if (!prof_on)
597        return 0;
598
599    cpu_notifier_register_begin();
600
601    if (create_hash_tables()) {
602        err = -ENOMEM;
603        goto out;
604    }
605
606    entry = proc_create("profile", S_IWUSR | S_IRUGO,
607                NULL, &proc_profile_operations);
608    if (!entry)
609        goto out;
610    proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
611    __hotcpu_notifier(profile_cpu_callback, 0);
612
613out:
614    cpu_notifier_register_done();
615    return err;
616}
617subsys_initcall(create_proc_profile);
618#endif /* CONFIG_PROC_FS */
619

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