ftrace: modulize the number of CPU buffers
Currently ftrace allocates a trace buffer for every possible CPU.
Work is being done to change it to only online CPUs and add hooks
to hotplug CPUS.
This patch lays out the infrastructure for such a change.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 290e9da..5da391c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -35,6 +35,12 @@
unsigned long __read_mostly tracing_max_latency = (cycle_t)ULONG_MAX;
unsigned long __read_mostly tracing_thresh;
+static unsigned long __read_mostly tracing_nr_buffers;
+static cpumask_t __read_mostly tracing_buffer_mask;
+
+#define for_each_tracing_cpu(cpu) \
+ for_each_cpu_mask(cpu, tracing_buffer_mask)
+
/* dummy trace to disable tracing */
static struct tracer no_tracer __read_mostly = {
.name = "none",
@@ -328,7 +334,7 @@
WARN_ON_ONCE(!irqs_disabled());
__raw_spin_lock(&ftrace_max_lock);
/* clear out all the previous traces */
- for_each_possible_cpu(i) {
+ for_each_tracing_cpu(i) {
data = tr->data[i];
flip_trace(max_tr.data[i], data);
tracing_reset(data);
@@ -352,7 +358,7 @@
WARN_ON_ONCE(!irqs_disabled());
__raw_spin_lock(&ftrace_max_lock);
- for_each_possible_cpu(i)
+ for_each_tracing_cpu(i)
tracing_reset(max_tr.data[i]);
flip_trace(max_tr.data[cpu], data);
@@ -398,7 +404,7 @@
* internal tracing to verify that everything is in order.
* If we fail, we do not register this tracer.
*/
- for_each_possible_cpu(i) {
+ for_each_tracing_cpu(i) {
data = tr->data[i];
if (!head_page(data))
continue;
@@ -417,7 +423,7 @@
goto out;
}
/* Only reset on passing, to avoid touching corrupted buffers */
- for_each_possible_cpu(i) {
+ for_each_tracing_cpu(i) {
data = tr->data[i];
if (!head_page(data))
continue;
@@ -847,7 +853,7 @@
int next_cpu = -1;
int cpu;
- for_each_possible_cpu(cpu) {
+ for_each_tracing_cpu(cpu) {
if (!head_page(tr->data[cpu]))
continue;
ent = trace_entry_idx(tr, tr->data[cpu], iter, cpu);
@@ -972,7 +978,7 @@
iter->prev_ent = NULL;
iter->prev_cpu = -1;
- for_each_possible_cpu(i) {
+ for_each_tracing_cpu(i) {
iter->next_idx[i] = 0;
iter->next_page[i] = NULL;
}
@@ -1089,7 +1095,7 @@
if (type)
name = type->name;
- for_each_possible_cpu(cpu) {
+ for_each_tracing_cpu(cpu) {
if (head_page(tr->data[cpu])) {
total += tr->data[cpu]->trace_idx;
if (tr->data[cpu]->trace_idx > tr->entries)
@@ -1519,7 +1525,7 @@
struct trace_array_cpu *data;
int cpu;
- for_each_possible_cpu(cpu) {
+ for_each_tracing_cpu(cpu) {
data = iter->tr->data[cpu];
if (head_page(data) && data->trace_idx &&
@@ -1831,7 +1837,7 @@
raw_local_irq_disable();
__raw_spin_lock(&ftrace_max_lock);
- for_each_possible_cpu(cpu) {
+ for_each_tracing_cpu(cpu) {
/*
* Increase/decrease the disabled counter if we are
* about to flip a bit in the cpumask:
@@ -2308,7 +2314,7 @@
ftrace_enabled = 0;
#endif
smp_wmb();
- for_each_possible_cpu(cpu) {
+ for_each_tracing_cpu(cpu) {
data = iter->tr->data[cpu];
if (!head_page(data) || !data->trace_idx)
@@ -2605,7 +2611,7 @@
int i;
/* first allocate a page for each CPU */
- for_each_possible_cpu(i) {
+ for_each_tracing_cpu(i) {
array = (void *)__get_free_page(GFP_KERNEL);
if (array == NULL) {
printk(KERN_ERR "tracer: failed to allocate page"
@@ -2630,7 +2636,7 @@
}
/* Now that we successfully allocate a page per CPU, add them */
- for_each_possible_cpu(i) {
+ for_each_tracing_cpu(i) {
data = global_trace.data[i];
page = list_entry(pages.next, struct page, lru);
list_del_init(&page->lru);
@@ -2666,7 +2672,7 @@
int ret = 0;
/* free one page from each buffer */
- for_each_possible_cpu(i) {
+ for_each_tracing_cpu(i) {
data = global_trace.data[i];
p = data->trace_pages.next;
if (p == &data->trace_pages) {
@@ -2717,8 +2723,12 @@
global_trace.ctrl = tracer_enabled;
+ /* TODO: make the number of buffers hot pluggable with CPUS */
+ tracing_nr_buffers = num_possible_cpus();
+ tracing_buffer_mask = cpu_possible_map;
+
/* Allocate the first page for all buffers */
- for_each_possible_cpu(i) {
+ for_each_tracing_cpu(i) {
data = global_trace.data[i] = &per_cpu(global_trace_cpu, i);
max_tr.data[i] = &per_cpu(max_data, i);