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Subject[PATCH 1/3] 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>
---
kernel/trace/trace.c | 16 +++++++++++-----
kernel/trace/trace.h | 6 +++++-
2 files changed, 16 insertions(+), 6 deletions(-)

Index: linux-sched-devel.git/kernel/trace/trace.c
===================================================================
--- linux-sched-devel.git.orig/kernel/trace/trace.c 2008-04-21 13:47:30.000000000 -0400
+++ linux-sched-devel.git/kernel/trace/trace.c 2008-04-21 14:39:43.000000000 -0400
@@ -612,6 +612,7 @@ void unregister_tracer(struct tracer *ty
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;
@@ -753,6 +754,7 @@ tracing_get_trace_entry(struct trace_arr
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 =
@@ -2398,8 +2400,6 @@ tracing_read_pipe(struct file *filp, cha
{
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;
@@ -2478,10 +2478,11 @@ tracing_read_pipe(struct file *filp, cha
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
@@ -2510,6 +2511,11 @@ tracing_read_pipe(struct file *filp, cha
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) {
Index: linux-sched-devel.git/kernel/trace/trace.h
===================================================================
--- linux-sched-devel.git.orig/kernel/trace/trace.h 2008-04-21 13:47:30.000000000 -0400
+++ linux-sched-devel.git/kernel/trace/trace.h 2008-04-21 14:38:09.000000000 -0400
@@ -102,6 +102,7 @@ struct trace_array_cpu {
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;
@@ -162,10 +163,13 @@ struct trace_seq {
* 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;

--


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