ftrace: add logic to record overruns
This patch sets up the infrastructure to record overruns of the tracing
buffer.
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 1281969..b9126ef 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -609,6 +609,7 @@
void tracing_reset(struct trace_array_cpu *data)
{
data->trace_idx = 0;
+ data->overrun = 0;
data->trace_head = data->trace_tail = head_page(data);
data->trace_head_idx = 0;
data->trace_tail_idx = 0;
@@ -750,6 +751,7 @@
if (data->trace_head == data->trace_tail &&
idx_next == data->trace_tail_idx) {
/* overrun */
+ data->overrun++;
data->trace_tail_idx++;
if (data->trace_tail_idx >= ENTRIES_PER_PAGE) {
data->trace_tail =
@@ -2353,8 +2355,6 @@
{
struct trace_iterator *iter = filp->private_data;
struct trace_array_cpu *data;
- struct trace_array *tr = iter->tr;
- struct tracer *tracer = iter->trace;
static cpumask_t mask;
static int start;
unsigned long flags;
@@ -2433,10 +2433,11 @@
if (cnt >= PAGE_SIZE)
cnt = PAGE_SIZE - 1;
- memset(iter, 0, sizeof(*iter));
- iter->tr = tr;
- iter->trace = tracer;
+ /* reset all but tr, trace, and overruns */
iter->pos = -1;
+ memset(&iter->seq, 0,
+ sizeof(struct trace_iterator) -
+ offsetof(struct trace_iterator, seq));
/*
* We need to stop all tracing on all CPUS to read the
@@ -2465,6 +2466,11 @@
for_each_cpu_mask(cpu, mask) {
data = iter->tr->data[cpu];
__raw_spin_lock(&data->lock);
+
+ if (data->overrun > iter->last_overrun[cpu])
+ iter->overrun[cpu] +=
+ data->overrun - iter->last_overrun[cpu];
+ iter->last_overrun[cpu] = data->overrun;
}
while (find_next_entry_inc(iter) != NULL) {
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 8991c5e..c1ec134 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -97,6 +97,7 @@
void *trace_head; /* producer */
void *trace_tail; /* consumer */
unsigned long trace_idx;
+ unsigned long overrun;
unsigned long saved_latency;
unsigned long critical_start;
unsigned long critical_end;
@@ -157,10 +158,13 @@
* results to users and which routines might sleep, etc:
*/
struct trace_iterator {
- struct trace_seq seq;
struct trace_array *tr;
struct tracer *trace;
+ long last_overrun[NR_CPUS];
+ long overrun[NR_CPUS];
+ /* The below is zeroed out in pipe_read */
+ struct trace_seq seq;
struct trace_entry *ent;
int cpu;