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Subject[PATCH v4 2/3] tracing: Add trace_total_entries() / trace_total_entries_cpu()
Date
These two new exported functions will be used in a future patch by
kdb_ftdump() to quickly skip all but the last few trace entries.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

Changes in v4:
- trace_total_entries() / trace_total_entries_cpu() new for v4

Changes in v3: None

kernel/trace/trace.c | 65 ++++++++++++++++++++++++++++++++++----------
kernel/trace/trace.h | 3 ++
2 files changed, 53 insertions(+), 15 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ccd759eaad79..7afc90f82e53 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3490,34 +3490,69 @@ static void s_stop(struct seq_file *m, void *p)
trace_event_read_unlock();
}

+static void
+get_total_entries_cpu(struct trace_buffer *buf, unsigned long *total,
+ unsigned long *entries, int cpu)
+{
+ unsigned long count;
+
+ count = ring_buffer_entries_cpu(buf->buffer, cpu);
+ /*
+ * If this buffer has skipped entries, then we hold all
+ * entries for the trace and we need to ignore the
+ * ones before the time stamp.
+ */
+ if (per_cpu_ptr(buf->data, cpu)->skipped_entries) {
+ count -= per_cpu_ptr(buf->data, cpu)->skipped_entries;
+ /* total is the same as the entries */
+ *total = count;
+ } else
+ *total = count +
+ ring_buffer_overrun_cpu(buf->buffer, cpu);
+ *entries = count;
+}
+
static void
get_total_entries(struct trace_buffer *buf,
unsigned long *total, unsigned long *entries)
{
- unsigned long count;
+ unsigned long t, e;
int cpu;

*total = 0;
*entries = 0;

for_each_tracing_cpu(cpu) {
- count = ring_buffer_entries_cpu(buf->buffer, cpu);
- /*
- * If this buffer has skipped entries, then we hold all
- * entries for the trace and we need to ignore the
- * ones before the time stamp.
- */
- if (per_cpu_ptr(buf->data, cpu)->skipped_entries) {
- count -= per_cpu_ptr(buf->data, cpu)->skipped_entries;
- /* total is the same as the entries */
- *total += count;
- } else
- *total += count +
- ring_buffer_overrun_cpu(buf->buffer, cpu);
- *entries += count;
+ get_total_entries_cpu(buf, &t, &e, cpu);
+ *total += t;
+ *entries += e;
}
}

+unsigned long trace_total_entries_cpu(struct trace_array *tr, int cpu)
+{
+ unsigned long total, entries;
+
+ if (!tr)
+ tr = &global_trace;
+
+ get_total_entries_cpu(&tr->trace_buffer, &total, &entries, cpu);
+
+ return entries;
+}
+
+unsigned long trace_total_entries(struct trace_array *tr)
+{
+ unsigned long total, entries;
+
+ if (!tr)
+ tr = &global_trace;
+
+ get_total_entries(&tr->trace_buffer, &total, &entries);
+
+ return entries;
+}
+
static void print_lat_help_header(struct seq_file *m)
{
seq_puts(m, "# _------=> CPU# \n"
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index d80cee49e0eb..4562b30eda9d 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -719,6 +719,9 @@ void trace_init_global_iter(struct trace_iterator *iter);

void tracing_iter_reset(struct trace_iterator *iter, int cpu);

+unsigned long trace_total_entries_cpu(struct trace_array *tr, int cpu);
+unsigned long trace_total_entries(struct trace_array *tr);
+
void trace_function(struct trace_array *tr,
unsigned long ip,
unsigned long parent_ip,
--
2.21.0.360.g471c308f928-goog
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