From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Peter Wu <peter@lekensteyn.nl>, Jonathan Corbet <corbet@lwn.net>,
Tom Zanussi <zanussi@kernel.org>
Subject: [RFC][PATCH 10/11] ring-buffer/tracing: Have iterator acknowledge dropped events
Date: Tue, 17 Mar 2020 17:32:32 -0400 [thread overview]
Message-ID: <20200317213417.045858900@goodmis.org> (raw)
In-Reply-To: 20200317213222.421100128@goodmis.org
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Have the ring_buffer_iterator set a flag if events were dropped as it were
to go and peek at the next event. Have the trace file display this fact if
it happened with a "LOST EVENTS" message.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
include/linux/ring_buffer.h | 1 +
kernel/trace/ring_buffer.c | 16 ++++++++++++++++
kernel/trace/trace.c | 16 ++++++++++++----
3 files changed, 29 insertions(+), 4 deletions(-)
diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index 0ae603b79b0e..c76b2f3b3ac4 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -138,6 +138,7 @@ ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts);
void ring_buffer_iter_advance(struct ring_buffer_iter *iter);
void ring_buffer_iter_reset(struct ring_buffer_iter *iter);
int ring_buffer_iter_empty(struct ring_buffer_iter *iter);
+bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter);
unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu);
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 8bafba674ec0..87bbb519505f 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -510,6 +510,7 @@ struct ring_buffer_iter {
u64 read_stamp;
u64 page_stamp;
struct ring_buffer_event *event;
+ int missed_events;
};
/**
@@ -1971,6 +1972,7 @@ rb_iter_head_event(struct ring_buffer_iter *iter)
iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
iter->head = 0;
iter->next_event = 0;
+ iter->missed_events = 1;
return NULL;
}
@@ -4174,6 +4176,20 @@ ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
return event;
}
+/** ring_buffer_iter_dropped - report if there are dropped events
+ * @iter: The ring buffer iterator
+ *
+ * Returns true if there was dropped events since the last peek.
+ */
+bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
+{
+ bool ret = iter->missed_events != 0;
+
+ iter->missed_events = 0;
+ return ret;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
+
/**
* ring_buffer_iter_peek - peek at the next event to be read
* @iter: The ring buffer iterator
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a60f49c401f9..65eb38131b6d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3388,11 +3388,15 @@ peek_next_entry(struct trace_iterator *iter, int cpu, u64 *ts,
struct ring_buffer_event *event;
struct ring_buffer_iter *buf_iter = trace_buffer_iter(iter, cpu);
- if (buf_iter)
+ if (buf_iter) {
event = ring_buffer_iter_peek(buf_iter, ts);
- else
+ if (lost_events)
+ *lost_events = ring_buffer_iter_dropped(buf_iter) ?
+ (unsigned long)-1 : 0;
+ } else {
event = ring_buffer_peek(iter->array_buffer->buffer, cpu, ts,
lost_events);
+ }
if (event) {
iter->ent_size = ring_buffer_event_length(event);
@@ -4005,8 +4009,12 @@ enum print_line_t print_trace_line(struct trace_iterator *iter)
enum print_line_t ret;
if (iter->lost_events) {
- trace_seq_printf(&iter->seq, "CPU:%d [LOST %lu EVENTS]\n",
- iter->cpu, iter->lost_events);
+ if (iter->lost_events == (unsigned long)-1)
+ trace_seq_printf(&iter->seq, "CPU:%d [LOST EVENTS]\n",
+ iter->cpu);
+ else
+ trace_seq_printf(&iter->seq, "CPU:%d [LOST %lu EVENTS]\n",
+ iter->cpu, iter->lost_events);
if (trace_seq_has_overflowed(&iter->seq))
return TRACE_TYPE_PARTIAL_LINE;
}
--
2.25.1
next prev parent reply other threads:[~2020-03-17 21:35 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-17 21:32 [RFC][PATCH 00/11] ring-buffer/tracing: Remove disabling of ring buffer while reading trace file Steven Rostedt
2020-03-17 21:32 ` [RFC][PATCH 01/11] tracing: Save off entry when peeking at next entry Steven Rostedt
2020-03-19 13:41 ` Masami Hiramatsu
2020-03-19 19:53 ` Steven Rostedt
2020-03-17 21:32 ` [RFC][PATCH 02/11] ring-buffer: Have ring_buffer_empty() not depend on tracing stopped Steven Rostedt
2020-03-17 21:32 ` [RFC][PATCH 03/11] ring-buffer: Rename ring_buffer_read() to read_buffer_iter_advance() Steven Rostedt
2020-03-17 21:32 ` [RFC][PATCH 04/11] ring-buffer: Add page_stamp to iterator for synchronization Steven Rostedt
2020-03-17 21:32 ` [RFC][PATCH 05/11] ring-buffer: Have rb_iter_head_event() handle concurrent writer Steven Rostedt
2020-03-17 21:32 ` [RFC][PATCH 06/11] ring-buffer: Do not die if rb_iter_peek() fails more than thrice Steven Rostedt
2020-03-17 21:32 ` [RFC][PATCH 07/11] ring-buffer: Optimize rb_iter_head_event() Steven Rostedt
2020-03-17 21:32 ` [RFC][PATCH 08/11] ring-buffer: Do not disable recording when there is an iterator Steven Rostedt
2020-03-17 21:32 ` [RFC][PATCH 09/11] tracing: Do not disable tracing when reading the trace file Steven Rostedt
2020-03-17 21:32 ` Steven Rostedt [this message]
2020-03-17 21:32 ` [RFC][PATCH 11/11] tracing: Have the document reflect that the trace file keeps tracing enabled Steven Rostedt
2020-03-18 15:13 ` [RFC][PATCH 12/11] selftest/ftrace: Fix function trigger test to handle trace not disabling the tracer Steven Rostedt
2020-03-18 16:35 ` Shuah Khan
2020-03-19 13:04 ` Masami Hiramatsu
2020-03-19 5:27 ` [RFC][PATCH 00/11] ring-buffer/tracing: Remove disabling of ring buffer while reading trace file Alexei Starovoitov
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