From cafb168a1c92e4c9e1731fe3d666c39611762c49 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Tue, 24 Mar 2009 20:50:39 -0400 Subject: [PATCH] tracing: make the function profiler per cpu Impact: speed enhancement By making the function profiler record in per cpu data we not only get better readings, avoid races, we also do not have to take any locks. Signed-off-by: Steven Rostedt --- kernel/trace/ftrace.c | 199 +++++++++++++++++++++++++++--------------- 1 file changed, 130 insertions(+), 69 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index a9ccd71fc922..ed1fc5021d44 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -257,28 +257,28 @@ struct ftrace_profile_page { struct ftrace_profile records[]; }; +struct ftrace_profile_stat { + atomic_t disabled; + struct hlist_head *hash; + struct ftrace_profile_page *pages; + struct ftrace_profile_page *start; + struct tracer_stat stat; +}; + #define PROFILE_RECORDS_SIZE \ (PAGE_SIZE - offsetof(struct ftrace_profile_page, records)) #define PROFILES_PER_PAGE \ (PROFILE_RECORDS_SIZE / sizeof(struct ftrace_profile)) -/* TODO: make these percpu, to prevent cache line bouncing */ -static struct ftrace_profile_page *profile_pages_start; -static struct ftrace_profile_page *profile_pages; - -static struct hlist_head *ftrace_profile_hash; static int ftrace_profile_bits; static int ftrace_profile_enabled; static DEFINE_MUTEX(ftrace_profile_lock); -static DEFINE_PER_CPU(atomic_t, ftrace_profile_disable); +static DEFINE_PER_CPU(struct ftrace_profile_stat, ftrace_profile_stats); #define FTRACE_PROFILE_HASH_SIZE 1024 /* must be power of 2 */ -static raw_spinlock_t ftrace_profile_rec_lock = - (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED; - static void * function_stat_next(void *v, int idx) { @@ -303,7 +303,13 @@ function_stat_next(void *v, int idx) static void *function_stat_start(struct tracer_stat *trace) { - return function_stat_next(&profile_pages_start->records[0], 0); + struct ftrace_profile_stat *stat = + container_of(trace, struct ftrace_profile_stat, stat); + + if (!stat || !stat->start) + return NULL; + + return function_stat_next(&stat->start->records[0], 0); } #ifdef CONFIG_FUNCTION_GRAPH_TRACER @@ -374,20 +380,11 @@ static int function_stat_show(struct seq_file *m, void *v) return 0; } -static struct tracer_stat function_stats = { - .name = "functions", - .stat_start = function_stat_start, - .stat_next = function_stat_next, - .stat_cmp = function_stat_cmp, - .stat_headers = function_stat_headers, - .stat_show = function_stat_show -}; - -static void ftrace_profile_reset(void) +static void ftrace_profile_reset(struct ftrace_profile_stat *stat) { struct ftrace_profile_page *pg; - pg = profile_pages = profile_pages_start; + pg = stat->pages = stat->start; while (pg) { memset(pg->records, 0, PROFILE_RECORDS_SIZE); @@ -395,24 +392,24 @@ static void ftrace_profile_reset(void) pg = pg->next; } - memset(ftrace_profile_hash, 0, + memset(stat->hash, 0, FTRACE_PROFILE_HASH_SIZE * sizeof(struct hlist_head)); } -int ftrace_profile_pages_init(void) +int ftrace_profile_pages_init(struct ftrace_profile_stat *stat) { struct ftrace_profile_page *pg; int i; /* If we already allocated, do nothing */ - if (profile_pages) + if (stat->pages) return 0; - profile_pages = (void *)get_zeroed_page(GFP_KERNEL); - if (!profile_pages) + stat->pages = (void *)get_zeroed_page(GFP_KERNEL); + if (!stat->pages) return -ENOMEM; - pg = profile_pages_start = profile_pages; + pg = stat->start = stat->pages; /* allocate 10 more pages to start */ for (i = 0; i < 10; i++) { @@ -430,13 +427,16 @@ int ftrace_profile_pages_init(void) return 0; } -static int ftrace_profile_init(void) +static int ftrace_profile_init_cpu(int cpu) { + struct ftrace_profile_stat *stat; int size; - if (ftrace_profile_hash) { + stat = &per_cpu(ftrace_profile_stats, cpu); + + if (stat->hash) { /* If the profile is already created, simply reset it */ - ftrace_profile_reset(); + ftrace_profile_reset(stat); return 0; } @@ -446,29 +446,45 @@ static int ftrace_profile_init(void) */ size = FTRACE_PROFILE_HASH_SIZE; - ftrace_profile_hash = - kzalloc(sizeof(struct hlist_head) * size, GFP_KERNEL); + stat->hash = kzalloc(sizeof(struct hlist_head) * size, GFP_KERNEL); - if (!ftrace_profile_hash) + if (!stat->hash) return -ENOMEM; - size--; + if (!ftrace_profile_bits) { + size--; - for (; size; size >>= 1) - ftrace_profile_bits++; + for (; size; size >>= 1) + ftrace_profile_bits++; + } /* Preallocate a few pages */ - if (ftrace_profile_pages_init() < 0) { - kfree(ftrace_profile_hash); - ftrace_profile_hash = NULL; + if (ftrace_profile_pages_init(stat) < 0) { + kfree(stat->hash); + stat->hash = NULL; return -ENOMEM; } return 0; } +static int ftrace_profile_init(void) +{ + int cpu; + int ret = 0; + + for_each_online_cpu(cpu) { + ret = ftrace_profile_init_cpu(cpu); + if (ret) + break; + } + + return ret; +} + /* interrupts must be disabled */ -static struct ftrace_profile *ftrace_find_profiled_func(unsigned long ip) +static struct ftrace_profile * +ftrace_find_profiled_func(struct ftrace_profile_stat *stat, unsigned long ip) { struct ftrace_profile *rec; struct hlist_head *hhd; @@ -476,7 +492,7 @@ static struct ftrace_profile *ftrace_find_profiled_func(unsigned long ip) unsigned long key; key = hash_long(ip, ftrace_profile_bits); - hhd = &ftrace_profile_hash[key]; + hhd = &stat->hash[key]; if (hlist_empty(hhd)) return NULL; @@ -489,52 +505,50 @@ static struct ftrace_profile *ftrace_find_profiled_func(unsigned long ip) return NULL; } -static void ftrace_add_profile(struct ftrace_profile *rec) +static void ftrace_add_profile(struct ftrace_profile_stat *stat, + struct ftrace_profile *rec) { unsigned long key; key = hash_long(rec->ip, ftrace_profile_bits); - hlist_add_head_rcu(&rec->node, &ftrace_profile_hash[key]); + hlist_add_head_rcu(&rec->node, &stat->hash[key]); } /* Interrupts must be disabled calling this */ static struct ftrace_profile * -ftrace_profile_alloc(unsigned long ip, bool alloc_safe) +ftrace_profile_alloc(struct ftrace_profile_stat *stat, + unsigned long ip, bool alloc_safe) { struct ftrace_profile *rec = NULL; /* prevent recursion */ - if (atomic_inc_return(&__get_cpu_var(ftrace_profile_disable)) != 1) + if (atomic_inc_return(&stat->disabled) != 1) goto out; - __raw_spin_lock(&ftrace_profile_rec_lock); - /* Try to always keep another page available */ - if (!profile_pages->next && alloc_safe) - profile_pages->next = (void *)get_zeroed_page(GFP_ATOMIC); + if (!stat->pages->next && alloc_safe) + stat->pages->next = (void *)get_zeroed_page(GFP_ATOMIC); /* * Try to find the function again since another * task on another CPU could have added it */ - rec = ftrace_find_profiled_func(ip); + rec = ftrace_find_profiled_func(stat, ip); if (rec) - goto out_unlock; + goto out; - if (profile_pages->index == PROFILES_PER_PAGE) { - if (!profile_pages->next) - goto out_unlock; - profile_pages = profile_pages->next; + if (stat->pages->index == PROFILES_PER_PAGE) { + if (!stat->pages->next) + goto out; + stat->pages = stat->pages->next; } - rec = &profile_pages->records[profile_pages->index++]; + rec = &stat->pages->records[stat->pages->index++]; rec->ip = ip; - ftrace_add_profile(rec); + ftrace_add_profile(stat, rec); - out_unlock: - __raw_spin_unlock(&ftrace_profile_rec_lock); out: - atomic_dec(&__get_cpu_var(ftrace_profile_disable)); + atomic_dec(&stat->disabled); return rec; } @@ -552,6 +566,7 @@ static bool ftrace_safe_to_allocate(void) static void function_profile_call(unsigned long ip, unsigned long parent_ip) { + struct ftrace_profile_stat *stat; struct ftrace_profile *rec; unsigned long flags; bool alloc_safe; @@ -562,9 +577,14 @@ function_profile_call(unsigned long ip, unsigned long parent_ip) alloc_safe = ftrace_safe_to_allocate(); local_irq_save(flags); - rec = ftrace_find_profiled_func(ip); + + stat = &__get_cpu_var(ftrace_profile_stats); + if (!stat->hash) + goto out; + + rec = ftrace_find_profiled_func(stat, ip); if (!rec) { - rec = ftrace_profile_alloc(ip, alloc_safe); + rec = ftrace_profile_alloc(stat, ip, alloc_safe); if (!rec) goto out; } @@ -583,13 +603,19 @@ static int profile_graph_entry(struct ftrace_graph_ent *trace) static void profile_graph_return(struct ftrace_graph_ret *trace) { - unsigned long flags; + struct ftrace_profile_stat *stat; struct ftrace_profile *rec; + unsigned long flags; local_irq_save(flags); - rec = ftrace_find_profiled_func(trace->func); + stat = &__get_cpu_var(ftrace_profile_stats); + if (!stat->hash) + goto out; + + rec = ftrace_find_profiled_func(stat, trace->func); if (rec) rec->time += trace->rettime - trace->calltime; + out: local_irq_restore(flags); } @@ -687,16 +713,51 @@ static const struct file_operations ftrace_profile_fops = { .write = ftrace_profile_write, }; +/* used to initialize the real stat files */ +static struct tracer_stat function_stats __initdata = { + .name = "functions", + .stat_start = function_stat_start, + .stat_next = function_stat_next, + .stat_cmp = function_stat_cmp, + .stat_headers = function_stat_headers, + .stat_show = function_stat_show +}; + static void ftrace_profile_debugfs(struct dentry *d_tracer) { + struct ftrace_profile_stat *stat; struct dentry *entry; + char *name; int ret; + int cpu; - ret = register_stat_tracer(&function_stats); - if (ret) { - pr_warning("Warning: could not register " - "function stats\n"); - return; + for_each_possible_cpu(cpu) { + stat = &per_cpu(ftrace_profile_stats, cpu); + + /* allocate enough for function name + cpu number */ + name = kmalloc(32, GFP_KERNEL); + if (!name) { + /* + * The files created are permanent, if something happens + * we still do not free memory. + */ + kfree(stat); + WARN(1, + "Could not allocate stat file for cpu %d\n", + cpu); + return; + } + stat->stat = function_stats; + snprintf(name, 32, "function%d", cpu); + stat->stat.name = name; + ret = register_stat_tracer(&stat->stat); + if (ret) { + WARN(1, + "Could not register function stat for cpu %d\n", + cpu); + kfree(name); + return; + } } entry = debugfs_create_file("function_profile_enabled", 0644, -- 2.34.1