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kernel/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, |
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* Nadia Yvette Chambers, Oracle, July 2004 |
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* Amortized hit count accounting via per-cpu open-addressed hashtables |
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* to resolve timer interrupt livelocks, Nadia Yvette Chambers, * Oracle, 2004 |
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*/ |
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#include <linux/export.h> |
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#include <linux/profile.h> #include <linux/bootmem.h> #include <linux/notifier.h> #include <linux/mm.h> #include <linux/cpumask.h> #include <linux/cpu.h> |
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#include <linux/highmem.h> |
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#include <linux/mutex.h> |
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#include <linux/slab.h> #include <linux/vmalloc.h> |
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#include <linux/sched/stat.h> |
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#include <asm/sections.h> |
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#include <asm/irq_regs.h> |
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#include <asm/ptrace.h> |
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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) |
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static atomic_t *prof_buffer; static unsigned long prof_len, prof_shift; |
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int prof_on __read_mostly; |
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EXPORT_SYMBOL_GPL(prof_on); |
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static cpumask_var_t prof_cpu_mask; |
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#if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS) |
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static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits); static DEFINE_PER_CPU(int, cpu_profile_flip); |
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static DEFINE_MUTEX(profile_flip_mutex); |
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#endif /* CONFIG_SMP */ |
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int profile_setup(char *str) |
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{ |
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static const char schedstr[] = "schedule"; static const char sleepstr[] = "sleep"; static const char kvmstr[] = "kvm"; |
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int par; |
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if (!strncmp(str, sleepstr, strlen(sleepstr))) { |
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#ifdef CONFIG_SCHEDSTATS |
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force_schedstat_enabled(); |
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prof_on = SLEEP_PROFILING; if (str[strlen(sleepstr)] == ',') str += strlen(sleepstr) + 1; if (get_option(&str, &par)) prof_shift = par; |
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pr_info("kernel sleep profiling enabled (shift: %ld) ", |
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prof_shift); |
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#else |
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pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS "); |
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#endif /* CONFIG_SCHEDSTATS */ |
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} else if (!strncmp(str, schedstr, strlen(schedstr))) { |
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prof_on = SCHED_PROFILING; |
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if (str[strlen(schedstr)] == ',') str += strlen(schedstr) + 1; if (get_option(&str, &par)) prof_shift = par; |
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pr_info("kernel schedule profiling enabled (shift: %ld) ", |
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prof_shift); |
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} 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; |
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pr_info("kernel KVM profiling enabled (shift: %ld) ", |
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prof_shift); |
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} else if (get_option(&str, &par)) { |
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prof_shift = par; prof_on = CPU_PROFILING; |
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pr_info("kernel profiling enabled (shift: %ld) ", |
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prof_shift); } return 1; } __setup("profile=", profile_setup); |
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int __ref profile_init(void) |
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{ |
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int buffer_bytes; |
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if (!prof_on) |
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return 0; |
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|
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/* only text is profiled */ prof_len = (_etext - _stext) >> prof_shift; |
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buffer_bytes = prof_len*sizeof(atomic_t); |
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if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL)) return -ENOMEM; |
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cpumask_copy(prof_cpu_mask, cpu_possible_mask); |
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prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN); |
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if (prof_buffer) return 0; |
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prof_buffer = alloc_pages_exact(buffer_bytes, GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN); |
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if (prof_buffer) return 0; |
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prof_buffer = vzalloc(buffer_bytes); if (prof_buffer) |
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return 0; |
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free_cpumask_var(prof_cpu_mask); |
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return -ENOMEM; |
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} /* Profile event notifications */ |
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static BLOCKING_NOTIFIER_HEAD(task_exit_notifier); static ATOMIC_NOTIFIER_HEAD(task_free_notifier); static BLOCKING_NOTIFIER_HEAD(munmap_notifier); |
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void profile_task_exit(struct task_struct *task) |
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{ |
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blocking_notifier_call_chain(&task_exit_notifier, 0, task); |
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} |
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int profile_handoff_task(struct task_struct *task) |
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{ int ret; |
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ret = atomic_notifier_call_chain(&task_free_notifier, 0, task); |
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return (ret == NOTIFY_OK) ? 1 : 0; } void profile_munmap(unsigned long addr) { |
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blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr); |
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} |
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int task_handoff_register(struct notifier_block *n) |
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{ |
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return atomic_notifier_chain_register(&task_free_notifier, n); |
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} |
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EXPORT_SYMBOL_GPL(task_handoff_register); |
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|
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int task_handoff_unregister(struct notifier_block *n) |
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{ |
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return atomic_notifier_chain_unregister(&task_free_notifier, n); |
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} |
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EXPORT_SYMBOL_GPL(task_handoff_unregister); |
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|
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int profile_event_register(enum profile_type type, struct notifier_block *n) |
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{ int err = -EINVAL; |
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|
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switch (type) { |
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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; |
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} |
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return err; } |
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EXPORT_SYMBOL_GPL(profile_event_register); |
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int profile_event_unregister(enum profile_type type, struct notifier_block *n) |
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{ int err = -EINVAL; |
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switch (type) { |
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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; |
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} |
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return err; } |
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EXPORT_SYMBOL_GPL(profile_event_unregister); |
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#if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS) |
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/* * 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 |
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* SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from * process context). |
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* 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. * |
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* -- nyc |
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*/ 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; |
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mutex_lock(&profile_flip_mutex); |
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j = per_cpu(cpu_profile_flip, get_cpu()); put_cpu(); |
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on_each_cpu(__profile_flip_buffers, NULL, 1); |
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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; } } |
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mutex_unlock(&profile_flip_mutex); |
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} static void profile_discard_flip_buffers(void) { int i, cpu; |
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mutex_lock(&profile_flip_mutex); |
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i = per_cpu(cpu_profile_flip, get_cpu()); put_cpu(); |
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on_each_cpu(__profile_flip_buffers, NULL, 1); |
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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)); } |
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mutex_unlock(&profile_flip_mutex); |
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} |
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static void do_profile_hits(int type, void *__pc, unsigned int nr_hits) |
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{ unsigned long primary, secondary, flags, pc = (unsigned long)__pc; int i, j, cpu; struct profile_hit *hits; |
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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; } |
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/* * 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: */ |
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local_irq_save(flags); do { for (j = 0; j < PROFILE_GRPSZ; ++j) { if (hits[i + j].pc == pc) { |
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hits[i + j].hits += nr_hits; |
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goto out; } else if (!hits[i + j].hits) { hits[i + j].pc = pc; |
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hits[i + j].hits = nr_hits; |
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goto out; } } i = (i + secondary) & (NR_PROFILE_HIT - 1); } while (i != primary); |
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/* * Add the current hit(s) and flush the write-queue out * to the global buffer: */ atomic_add(nr_hits, &prof_buffer[pc]); |
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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(); } |
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static int profile_dead_cpu(unsigned int cpu) |
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{ |
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struct page *page; |
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int i; |
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if (prof_cpu_mask != NULL) cpumask_clear_cpu(cpu, prof_cpu_mask); for (i = 0; i < 2; i++) { if (per_cpu(cpu_profile_hits, cpu)[i]) { page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[i]); per_cpu(cpu_profile_hits, cpu)[i] = NULL; |
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__free_page(page); } |
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} return 0; } static int profile_prepare_cpu(unsigned int cpu) { int i, node = cpu_to_mem(cpu); struct page *page; per_cpu(cpu_profile_flip, cpu) = 0; for (i = 0; i < 2; i++) { if (per_cpu(cpu_profile_hits, cpu)[i]) continue; page = __alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0); if (!page) { profile_dead_cpu(cpu); return -ENOMEM; |
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} |
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per_cpu(cpu_profile_hits, cpu)[i] = page_address(page); |
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} |
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return 0; } static int profile_online_cpu(unsigned int cpu) { if (prof_cpu_mask != NULL) cpumask_set_cpu(cpu, prof_cpu_mask); return 0; |
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} |
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#else /* !CONFIG_SMP */ #define profile_flip_buffers() do { } while (0) #define profile_discard_flip_buffers() do { } while (0) |
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static void do_profile_hits(int type, void *__pc, unsigned int nr_hits) |
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{ unsigned long pc; |
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pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift; |
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atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]); |
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} #endif /* !CONFIG_SMP */ |
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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); } |
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EXPORT_SYMBOL_GPL(profile_hits); |
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void profile_tick(int type) |
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{ |
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struct pt_regs *regs = get_irq_regs(); |
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if (!user_mode(regs) && prof_cpu_mask != NULL && cpumask_test_cpu(smp_processor_id(), prof_cpu_mask)) |
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profile_hit(type, (void *)profile_pc(regs)); } #ifdef CONFIG_PROC_FS #include <linux/proc_fs.h> |
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#include <linux/seq_file.h> |
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#include <linux/uaccess.h> |
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static int prof_cpu_mask_proc_show(struct seq_file *m, void *v) |
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{ |
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seq_printf(m, "%*pb ", cpumask_pr_args(prof_cpu_mask)); |
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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); |
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} |
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static ssize_t prof_cpu_mask_proc_write(struct file *file, const char __user *buffer, size_t count, loff_t *pos) |
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{ |
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cpumask_var_t new_value; |
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int err; |
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if (!alloc_cpumask_var(&new_value, GFP_KERNEL)) return -ENOMEM; |
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err = cpumask_parse_user(buffer, count, new_value); if (!err) { |
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cpumask_copy(prof_cpu_mask, new_value); err = count; |
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} free_cpumask_var(new_value); return err; |
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} |
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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, }; |
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void create_prof_cpu_mask(void) |
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{ |
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/* create /proc/irq/prof_cpu_mask */ |
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proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_fops); |
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} /* * 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; |
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char *pnt; |
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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) { |
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if (put_user(*((char *)(&sample_step)+p), buf)) |
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return -EFAULT; |
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buf++; p++; count--; read++; } pnt = (char *)prof_buffer + p - sizeof(atomic_t); |
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if (copy_to_user(buf, (void *)pnt, count)) |
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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 |
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extern int setup_profiling_timer(unsigned int multiplier); |
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482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 |
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; } |
15ad7cdcf
|
497 |
static const struct file_operations proc_profile_operations = { |
1da177e4c
|
498 499 |
.read = read_profile, .write = write_profile, |
6038f373a
|
500 |
.llseek = default_llseek, |
1da177e4c
|
501 |
}; |
e722d8daa
|
502 |
int __ref create_proc_profile(void) |
1da177e4c
|
503 |
{ |
e722d8daa
|
504 505 506 |
struct proc_dir_entry *entry; #ifdef CONFIG_SMP enum cpuhp_state online_state; |
1da177e4c
|
507 |
#endif |
c270a8171
|
508 |
int err = 0; |
1da177e4c
|
509 510 511 |
if (!prof_on) return 0; |
e722d8daa
|
512 513 514 515 516 517 518 519 520 521 522 523 524 |
#ifdef CONFIG_SMP err = cpuhp_setup_state(CPUHP_PROFILE_PREPARE, "PROFILE_PREPARE", profile_prepare_cpu, profile_dead_cpu); if (err) return err; err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "AP_PROFILE_ONLINE", profile_online_cpu, NULL); if (err < 0) goto err_state_prep; online_state = err; err = 0; #endif |
c33fff0af
|
525 526 |
entry = proc_create("profile", S_IWUSR | S_IRUGO, NULL, &proc_profile_operations); |
1ad82fd54
|
527 |
if (!entry) |
e722d8daa
|
528 |
goto err_state_onl; |
271a15eab
|
529 |
proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t)); |
c270a8171
|
530 |
|
e722d8daa
|
531 532 533 534 535 536 537 |
return err; err_state_onl: #ifdef CONFIG_SMP cpuhp_remove_state(online_state); err_state_prep: cpuhp_remove_state(CPUHP_PROFILE_PREPARE); #endif |
c270a8171
|
538 |
return err; |
1da177e4c
|
539 |
} |
c96d6660d
|
540 |
subsys_initcall(create_proc_profile); |
1da177e4c
|
541 |
#endif /* CONFIG_PROC_FS */ |