Impact: reduce size of memory in function profiler
Backport to 2.6.29.3-rt14.
| From: Steven Rostedt <srostedt@xxxxxxxxxx>
|
| Impact: reduce size of memory in function profiler
|
| The function profiler originally introduces its counters into the
| function records itself. There is 20 thousand different functions on
| a normal system, and that is adding 20 thousand counters for profiling
| event when not needed.
|
| A normal run of the profiler yields only a couple of thousand functions
| executed, depending on what is being profiled. This means we have around
| 18 thousand useless counters.
|
| This patch rectifies this by moving the data out of the function
| records used by dynamic ftrace. Data is preallocated to hold the functions
| when the profiling begins. Checks are made during profiling to see if
| more recorcds should be allocated, and they are allocated if it is safe
| to do so.
|
| This also removes the dependency from using dynamic ftrace, and also
| removes the overhead by having it enabled.
|
| Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx>
Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@xxxxxxxxxx>
---
include/linux/ftrace.h | 4 -
kernel/trace/Kconfig | 10 +-
kernel/trace/ftrace.c | 440 ++++++++++++++++++++++++++++--------------------
3 files changed, 263 insertions(+), 191 deletions(-)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 0456c3a..015a3d2 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -153,11 +153,6 @@ struct dyn_ftrace {
unsigned long flags;
struct dyn_ftrace *newlist;
};
-#ifdef CONFIG_FUNCTION_PROFILER
- unsigned long counter;
- struct hlist_node node;
-#endif
-
struct dyn_arch_ftrace arch;
};
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 95e9ad5..8a41360 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -379,20 +379,16 @@ config DYNAMIC_FTRACE
config FUNCTION_PROFILER
bool "Kernel function profiler"
- depends on DYNAMIC_FTRACE
+ depends on FUNCTION_TRACER
default n
help
- This option enables the kernel function profiler. When the dynamic
- function tracing is enabled, a counter is added into the function
- records used by the dynamic function tracer. A file is created in
- debugfs called function_profile_enabled which defaults to zero.
+ This option enables the kernel function profiler. A file is created
+ in debugfs called function_profile_enabled which defaults to zero.
When a 1 is echoed into this file profiling begins, and when a
zero is entered, profiling stops. A file in the trace_stats
directory called functions, that show the list of functions that
have been hit and their counters.
- This takes up around 320K more memory.
-
If in doubt, say N
config FTRACE_MCOUNT_RECORD
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 11f364c..24dac44 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -241,87 +241,48 @@ static void ftrace_update_pid_func(void)
#endif
}
-/* set when tracing only a pid */
-struct pid *ftrace_pid_trace;
-static struct pid * const ftrace_swapper_pid = &init_struct_pid;
-
-#ifdef CONFIG_DYNAMIC_FTRACE
-
-#ifndef CONFIG_FTRACE_MCOUNT_RECORD
-# error Dynamic ftrace depends on MCOUNT_RECORD
-#endif
-
-static struct hlist_head ftrace_func_hash[FTRACE_FUNC_HASHSIZE] __read_mostly;
-
-struct ftrace_func_probe {
- struct hlist_node node;
- struct ftrace_probe_ops *ops;
- unsigned long flags;
- unsigned long ip;
- void *data;
- struct rcu_head rcu;
+#ifdef CONFIG_FUNCTION_PROFILER
+struct ftrace_profile {
+ struct hlist_node node;
+ unsigned long ip;
+ unsigned long counter;
};
-enum {
- FTRACE_ENABLE_CALLS = (1 << 0),
- FTRACE_DISABLE_CALLS = (1 << 1),
- FTRACE_UPDATE_TRACE_FUNC = (1 << 2),
- FTRACE_ENABLE_MCOUNT = (1 << 3),
- FTRACE_DISABLE_MCOUNT = (1 << 4),
- FTRACE_START_FUNC_RET = (1 << 5),
- FTRACE_STOP_FUNC_RET = (1 << 6),
+struct ftrace_profile_page {
+ struct ftrace_profile_page *next;
+ unsigned long index;
+ struct ftrace_profile records[];
};
-static int ftrace_filtered;
+#define PROFILE_RECORDS_SIZE \
+ (PAGE_SIZE - offsetof(struct ftrace_profile_page, records))
-static struct dyn_ftrace *ftrace_new_addrs;
+#define PROFILES_PER_PAGE \
+ (PROFILE_RECORDS_SIZE / sizeof(struct ftrace_profile))
-static DEFINE_MUTEX(ftrace_regex_lock);
-
-struct ftrace_page {
- struct ftrace_page *next;
- int index;
- struct dyn_ftrace records[];
-};
+/* TODO: make these percpu, to prevent cache line bouncing */
+static struct ftrace_profile_page *profile_pages_start;
+static struct ftrace_profile_page *profile_pages;
-#define ENTRIES_PER_PAGE \
- ((PAGE_SIZE - sizeof(struct ftrace_page)) / sizeof(struct dyn_ftrace))
-
-/* estimate from running different kernels */
-#define NR_TO_INIT 10000
-
-static struct ftrace_page *ftrace_pages_start;
-static struct ftrace_page *ftrace_pages;
-
-static struct dyn_ftrace *ftrace_free_records;
-
-/*
- * This is a double for. Do not use 'break' to break out of the loop,
- * you must use a goto.
- */
-#define do_for_each_ftrace_rec(pg, rec) \
- for (pg = ftrace_pages_start; pg; pg = pg->next) { \
- int _____i; \
- for (_____i = 0; _____i < pg->index; _____i++) { \
- rec = &pg->records[_____i];
-
-#define while_for_each_ftrace_rec() \
- } \
- }
-
-#ifdef CONFIG_FUNCTION_PROFILER
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);
+
+#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)
{
- struct dyn_ftrace *rec = v;
- struct ftrace_page *pg;
+ struct ftrace_profile *rec = v;
+ struct ftrace_profile_page *pg;
- pg = (struct ftrace_page *)((unsigned long)rec & PAGE_MASK);
+ pg = (struct ftrace_profile_page *)((unsigned long)rec & PAGE_MASK);
again:
rec++;
@@ -330,27 +291,22 @@ function_stat_next(void *v, int idx)
if (!pg)
return NULL;
rec = &pg->records[0];
+ if (!rec->counter)
+ goto again;
}
- if (rec->flags & FTRACE_FL_FREE ||
- rec->flags & FTRACE_FL_FAILED ||
- !(rec->flags & FTRACE_FL_CONVERTED) ||
- /* ignore non hit functions */
- !rec->counter)
- goto again;
-
return rec;
}
static void *function_stat_start(void)
{
- return function_stat_next(&ftrace_pages_start->records[0], 0);
+ return function_stat_next(&profile_pages_start->records[0], 0);
}
static int function_stat_cmp(void *p1, void *p2)
{
- struct dyn_ftrace *a = p1;
- struct dyn_ftrace *b = p2;
+ struct ftrace_profile *a = p1;
+ struct ftrace_profile *b = p2;
if (a->counter < b->counter)
return -1;
@@ -369,7 +325,7 @@ static int function_stat_headers(struct seq_file *m)
static int function_stat_show(struct seq_file *m, void *v)
{
- struct dyn_ftrace *rec = v;
+ struct ftrace_profile *rec = v;
char str[KSYM_SYMBOL_LEN];
kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
@@ -387,115 +343,191 @@ static struct tracer_stat function_stats = {
.stat_show = function_stat_show
};
-static void ftrace_profile_init(int nr_funcs)
+static void ftrace_profile_reset(void)
{
- unsigned long addr;
- int order;
- int size;
+ struct ftrace_profile_page *pg;
- /*
- * We are profiling all functions, lets make it 1/4th of the
- * number of functions that are in core kernel. So we have to
- * iterate 4 times.
- */
- order = (sizeof(struct hlist_head) * nr_funcs) / 4;
- order = get_order(order);
- size = 1 << (PAGE_SHIFT + order);
-
- pr_info("Allocating %d KB for profiler hash\n", size >> 10);
+ pg = profile_pages = profile_pages_start;
- addr = __get_free_pages(GFP_KERNEL | __GFP_ZERO, order);
- if (!addr) {
- pr_warning("Could not allocate function profiler hash\n");
- return;
+ while (pg) {
+ memset(pg->records, 0, PROFILE_RECORDS_SIZE);
+ pg->index = 0;
+ pg = pg->next;
}
- ftrace_profile_hash = (void *)addr;
+ memset(ftrace_profile_hash, 0,
+ FTRACE_PROFILE_HASH_SIZE * sizeof(struct hlist_head));
+}
- /*
- * struct hlist_head should be a pointer of 4 or 8 bytes.
- * And a simple bit manipulation can be done, but if for
- * some reason struct hlist_head is not a mulitple of 2,
- * then we play it safe, and simply count. This function
- * is done once at boot up, so it is not that critical in
- * performance.
- */
+int ftrace_profile_pages_init(void)
+{
+ struct ftrace_profile_page *pg;
+ int i;
- size--;
- size /= sizeof(struct hlist_head);
+ /* If we already allocated, do nothing */
+ if (profile_pages)
+ return 0;
- for (; size; size >>= 1)
- ftrace_profile_bits++;
+ profile_pages = (void *)get_zeroed_page(GFP_KERNEL);
+ if (!profile_pages)
+ return -ENOMEM;
- pr_info("Function profiler has %d hash buckets\n",
- 1 << ftrace_profile_bits);
+ pg = profile_pages_start = profile_pages;
- return;
+ /* allocate 10 more pages to start */
+ for (i = 0; i < 10; i++) {
+ pg->next = (void *)get_zeroed_page(GFP_KERNEL);
+ /*
+ * We only care about allocating profile_pages, if
+ * we failed to allocate here, hopefully we will allocate
+ * later.
+ */
+ if (!pg->next)
+ break;
+ pg = pg->next;
+ }
+
+ return 0;
}
-static ssize_t
-ftrace_profile_read(struct file *filp, char __user *ubuf,
- size_t cnt, loff_t *ppos)
+static int ftrace_profile_init(void)
{
- char buf[64];
- int r;
+ int size;
- r = sprintf(buf, "%u\n", ftrace_profile_enabled);
- return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
-}
+ if (ftrace_profile_hash) {
+ /* If the profile is already created, simply reset it */
+ ftrace_profile_reset();
+ return 0;
+ }
-static void ftrace_profile_reset(void)
-{
- struct dyn_ftrace *rec;
- struct ftrace_page *pg;
+ /*
+ * We are profiling all functions, but usually only a few thousand
+ * functions are hit. We'll make a hash of 1024 items.
+ */
+ size = FTRACE_PROFILE_HASH_SIZE;
- do_for_each_ftrace_rec(pg, rec) {
- rec->counter = 0;
- } while_for_each_ftrace_rec();
+ ftrace_profile_hash =
+ kzalloc(sizeof(struct hlist_head) * size, GFP_KERNEL);
+
+ if (!ftrace_profile_hash)
+ return -ENOMEM;
+
+ size--;
+
+ 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;
+ return -ENOMEM;
+ }
+
+ return 0;
}
-static struct dyn_ftrace *ftrace_find_profiled_func(unsigned long ip)
+/* interrupts must be disabled */
+static struct ftrace_profile *ftrace_find_profiled_func(unsigned long ip)
{
- struct dyn_ftrace *rec;
+ struct ftrace_profile *rec;
struct hlist_head *hhd;
struct hlist_node *n;
- unsigned long flags;
unsigned long key;
- if (!ftrace_profile_hash)
- return NULL;
-
key = hash_long(ip, ftrace_profile_bits);
hhd = &ftrace_profile_hash[key];
if (hlist_empty(hhd))
return NULL;
- local_irq_save(flags);
hlist_for_each_entry_rcu(rec, n, hhd, node) {
if (rec->ip == ip)
- goto out;
+ return rec;
+ }
+
+ return NULL;
+}
+
+static void ftrace_add_profile(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]);
+}
+
+/* Interrupts must be disabled calling this */
+static struct ftrace_profile *
+ftrace_profile_alloc(unsigned long ip, bool alloc_safe)
+{
+ struct ftrace_profile *rec = NULL;
+
+ /* prevent recursion */
+ if (atomic_inc_return(&__get_cpu_var(ftrace_profile_disable)) != 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);
+
+ /*
+ * Try to find the function again since another
+ * task on another CPU could have added it
+ */
+ rec = ftrace_find_profiled_func(ip);
+ if (rec)
+ goto out_unlock;
+
+ if (profile_pages->index == PROFILES_PER_PAGE) {
+ if (!profile_pages->next)
+ goto out_unlock;
+ profile_pages = profile_pages->next;
}
- rec = NULL;
+
+ rec = &profile_pages->records[profile_pages->index++];
+ rec->ip = ip;
+ ftrace_add_profile(rec);
+
+ out_unlock:
+ __raw_spin_unlock(&ftrace_profile_rec_lock);
out:
- local_irq_restore(flags);
+ atomic_dec(&__get_cpu_var(ftrace_profile_disable));
return rec;
}
+/*
+ * If we are not in an interrupt, or softirq and
+ * and interrupts are disabled and preemption is not enabled
+ * (not in a spinlock) then it should be safe to allocate memory.
+ */
+static bool ftrace_safe_to_allocate(void)
+{
+ return !in_interrupt() && irqs_disabled() && !preempt_count();
+}
+
static void
function_profile_call(unsigned long ip, unsigned long parent_ip)
{
- struct dyn_ftrace *rec;
+ struct ftrace_profile *rec;
unsigned long flags;
+ bool alloc_safe;
if (!ftrace_profile_enabled)
return;
+ alloc_safe = ftrace_safe_to_allocate();
+
local_irq_save(flags);
rec = ftrace_find_profiled_func(ip);
- if (!rec)
- goto out;
+ if (!rec) {
+ rec = ftrace_profile_alloc(ip, alloc_safe);
+ if (!rec)
+ goto out;
+ }
rec->counter++;
out:
@@ -515,11 +547,6 @@ ftrace_profile_write(struct file *filp, const char __user *ubuf,
char buf[64];
int ret;
- if (!ftrace_profile_hash) {
- pr_info("Can not enable hash due to earlier problems\n");
- return -ENODEV;
- }
-
if (cnt >= sizeof(buf))
return -EINVAL;
@@ -537,7 +564,12 @@ ftrace_profile_write(struct file *filp, const char __user *ubuf,
mutex_lock(&ftrace_profile_lock);
if (ftrace_profile_enabled ^ val) {
if (val) {
- ftrace_profile_reset();
+ ret = ftrace_profile_init();
+ if (ret < 0) {
+ cnt = ret;
+ goto out;
+ }
+
register_ftrace_function(&ftrace_profile_ops);
ftrace_profile_enabled = 1;
} else {
@@ -545,6 +577,7 @@ ftrace_profile_write(struct file *filp, const char __user *ubuf,
unregister_ftrace_function(&ftrace_profile_ops);
}
}
+ out:
mutex_unlock(&ftrace_profile_lock);
filp->f_pos += cnt;
@@ -552,6 +585,17 @@ ftrace_profile_write(struct file *filp, const char __user *ubuf,
return cnt;
}
+static ssize_t
+ftrace_profile_read(struct file *filp, char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ char buf[64];
+ int r;
+
+ r = sprintf(buf, "%u\n", ftrace_profile_enabled);
+ return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+}
+
static const struct file_operations ftrace_profile_fops = {
.open = tracing_open_generic,
.read = ftrace_profile_read,
@@ -577,39 +621,80 @@ static void ftrace_profile_debugfs(struct dentry *d_tracer)
"'function_profile_enabled' entry\n");
}
-static void ftrace_add_profile(struct dyn_ftrace *rec)
-{
- unsigned long key;
-
- if (!ftrace_profile_hash)
- return;
-
- key = hash_long(rec->ip, ftrace_profile_bits);
- hlist_add_head_rcu(&rec->node, &ftrace_profile_hash[key]);
-}
-
-static void ftrace_profile_release(struct dyn_ftrace *rec)
-{
- mutex_lock(&ftrace_profile_lock);
- hlist_del(&rec->node);
- mutex_unlock(&ftrace_profile_lock);
-}
-
#else /* CONFIG_FUNCTION_PROFILER */
-static void ftrace_profile_init(int nr_funcs)
-{
-}
-static void ftrace_add_profile(struct dyn_ftrace *rec)
-{
-}
static void ftrace_profile_debugfs(struct dentry *d_tracer)
{
}
-static void ftrace_profile_release(struct dyn_ftrace *rec)
-{
-}
#endif /* CONFIG_FUNCTION_PROFILER */
+/* set when tracing only a pid */
+struct pid *ftrace_pid_trace;
+static struct pid * const ftrace_swapper_pid = &init_struct_pid;
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+#ifndef CONFIG_FTRACE_MCOUNT_RECORD
+# error Dynamic ftrace depends on MCOUNT_RECORD
+#endif
+
+static struct hlist_head ftrace_func_hash[FTRACE_FUNC_HASHSIZE] __read_mostly;
+
+struct ftrace_func_probe {
+ struct hlist_node node;
+ struct ftrace_probe_ops *ops;
+ unsigned long flags;
+ unsigned long ip;
+ void *data;
+ struct rcu_head rcu;
+};
+
+enum {
+ FTRACE_ENABLE_CALLS = (1 << 0),
+ FTRACE_DISABLE_CALLS = (1 << 1),
+ FTRACE_UPDATE_TRACE_FUNC = (1 << 2),
+ FTRACE_ENABLE_MCOUNT = (1 << 3),
+ FTRACE_DISABLE_MCOUNT = (1 << 4),
+ FTRACE_START_FUNC_RET = (1 << 5),
+ FTRACE_STOP_FUNC_RET = (1 << 6),
+};
+
+static int ftrace_filtered;
+
+static struct dyn_ftrace *ftrace_new_addrs;
+
+static DEFINE_MUTEX(ftrace_regex_lock);
+
+struct ftrace_page {
+ struct ftrace_page *next;
+ int index;
+ struct dyn_ftrace records[];
+};
+
+#define ENTRIES_PER_PAGE \
+ ((PAGE_SIZE - sizeof(struct ftrace_page)) / sizeof(struct dyn_ftrace))
+
+/* estimate from running different kernels */
+#define NR_TO_INIT 10000
+
+static struct ftrace_page *ftrace_pages_start;
+static struct ftrace_page *ftrace_pages;
+
+static struct dyn_ftrace *ftrace_free_records;
+
+/*
+ * This is a double for. Do not use 'break' to break out of the loop,
+ * you must use a goto.
+ */
+#define do_for_each_ftrace_rec(pg, rec) \
+ for (pg = ftrace_pages_start; pg; pg = pg->next) { \
+ int _____i; \
+ for (_____i = 0; _____i < pg->index; _____i++) { \
+ rec = &pg->records[_____i];
+
+#define while_for_each_ftrace_rec() \
+ } \
+ }
+
#ifdef CONFIG_KPROBES
static int frozen_record_count;
@@ -660,10 +745,8 @@ void ftrace_release(void *start, unsigned long size)
mutex_lock(&ftrace_lock);
do_for_each_ftrace_rec(pg, rec) {
if ((rec->ip >= s) && (rec->ip < e) &&
- !(rec->flags & FTRACE_FL_FREE)) {
+ !(rec->flags & FTRACE_FL_FREE))
ftrace_free_rec(rec);
- ftrace_profile_release(rec);
- }
} while_for_each_ftrace_rec();
mutex_unlock(&ftrace_lock);
}
@@ -717,8 +800,6 @@ ftrace_record_ip(unsigned long ip)
rec->newlist = ftrace_new_addrs;
ftrace_new_addrs = rec;
- ftrace_add_profile(rec);
-
return rec;
}
@@ -2462,8 +2543,6 @@ static __init int ftrace_init_dyn_debugfs(struct dentry *d_tracer)
"'set_graph_function' entry\n");
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
- ftrace_profile_debugfs(d_tracer);
-
return 0;
}
@@ -2532,8 +2611,6 @@ void __init ftrace_init(void)
if (ret)
goto failed;
- ftrace_profile_init(count);
-
last_ftrace_enabled = ftrace_enabled = 1;
ret = ftrace_convert_nops(NULL,
@@ -2734,6 +2811,9 @@ static __init int ftrace_init_debugfs(void)
if (!entry)
pr_warning("Could not create debugfs "
"'set_ftrace_pid' entry\n");
+
+ ftrace_profile_debugfs(d_tracer);
+
return 0;
}
fs_initcall(ftrace_init_debugfs);
--
1.6.2
--
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
--
[ Luis Claudio R. Goncalves Bass - Gospel - RT ]
[ Fingerprint: 4FDD B8C4 3C59 34BD 8BE9 2696 7203 D980 A448 C8F8 ]
--
To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
