trace-cmd: Show lost events if buffer supports it

If the ring buffer in the kernel sends information via the commit field of the sub buffer header. Than this patch will display where events were lost. If the sub buffer has space and can store the count of dropped events, this patch will show the count as well. Signed-off-by: Steven Rostedt <[email protected]>
apolyudov · Apr 1, 2010 · 73effeb · 73effeb
1 parent 9492113
commit 73effeb
Show file tree

Hide file tree

Showing 4 changed files with 80 additions and 9 deletions.
diff --git a/parse-events.c b/parse-events.c
@@ -4041,11 +4041,16 @@ static void print_args(struct print_arg *args)
 }
 
 static void parse_header_field(const char *field,
-			       int *offset, int *size)
+			       int *offset, int *size, int mandatory)
 {
+	unsigned long long save_input_buf_ptr;
+	unsigned long long save_input_buf_siz;
 	char *token;
 	int type;
 
+	save_input_buf_ptr = input_buf_ptr;
+	save_input_buf_siz = input_buf_siz;
+
 	if (read_expected(EVENT_ITEM, "field") < 0)
 		return;
 	if (read_expected(EVENT_OP, ":") < 0)
@@ -4056,8 +4061,20 @@ static void parse_header_field(const char *field,
 		goto fail;
 	free_token(token);
 
-	if (read_expected(EVENT_ITEM, field) < 0)
-		return;
+	/*
+	 * If this is not a mandatory field, then test it first.
+	 */
+	if (mandatory) {
+		if (read_expected(EVENT_ITEM, field) < 0)
+			return;
+	} else {
+		if (read_expect_type(EVENT_ITEM, &token) < 0)
+			goto fail;
+		if (strcmp(token, field) != 0)
+			goto discard;
+		free_token(token);
+	}
+
 	if (read_expected(EVENT_OP, ";") < 0)
 		return;
 	if (read_expected(EVENT_ITEM, "offset") < 0)
@@ -4106,6 +4123,14 @@ static void parse_header_field(const char *field,
 	}
  fail:
 	free_token(token);
+	return;
+
+ discard:
+	input_buf_ptr = save_input_buf_ptr;
+	input_buf_siz = save_input_buf_siz;
+	*offset = 0;
+	*size = 0;
+	free_token(token);
 }
 
 /**
@@ -4123,6 +4148,8 @@ static void parse_header_field(const char *field,
 int pevent_parse_header_page(struct pevent *pevent, char *buf, unsigned long size,
 			     int long_size)
 {
+	int ignore;
+
 	if (!size) {
 		/*
 		 * Old kernels did not have header page info.
@@ -4137,11 +4164,13 @@ int pevent_parse_header_page(struct pevent *pevent, char *buf, unsigned long siz
 	init_input_buf(buf, size);
 
 	parse_header_field("timestamp", &pevent->header_page_ts_offset,
-			   &pevent->header_page_ts_size);
+			   &pevent->header_page_ts_size, 1);
 	parse_header_field("commit", &pevent->header_page_size_offset,
-			   &pevent->header_page_size_size);
+			   &pevent->header_page_size_size, 1);
+	parse_header_field("overwrite", &pevent->header_page_overwrite,
+			   &ignore, 0);
 	parse_header_field("data", &pevent->header_page_data_offset,
-			   &pevent->header_page_data_size);
+			   &pevent->header_page_data_size, 1);
 
 	return 0;
 }

diff --git a/parse-events.h b/parse-events.h
@@ -38,6 +38,7 @@
 struct record {
 	unsigned long long	ts;
 	unsigned long long	offset;
+	long long		missed_events;	/* buffer dropped events before */
 	int			record_size;	/* size of binary record */
 	int			size;		/* size of data */
 	void			*data;
@@ -284,6 +285,7 @@ struct pevent {
 	int header_page_size_size;
 	int header_page_data_offset;
 	int header_page_data_size;
+	int header_page_overwrite;
 
 	int file_bigendian;
 	int host_bigendian;

diff --git a/trace-input.c b/trace-input.c
@@ -39,6 +39,11 @@
 #include "trace-cmd-local.h"
 #include "list.h"
 
+#define MISSING_EVENTS (1 << 31)
+#define MISSING_STORED (1 << 30)
+
+#define COMMIT_MASK ((1 << 27) - 1)
+
 /* for debugging read instead of mmap */
 static int force_read = 0;
 
@@ -48,6 +53,7 @@ struct page {
 	struct tracecmd_input	*handle;
 	void			*map;
 	int			ref_count;
+	long long		lost_events;
 };
 
 struct cpu_data {
@@ -679,6 +685,7 @@ static int update_page_info(struct tracecmd_input *handle, int cpu)
 {
 	struct pevent *pevent = handle->pevent;
 	void *ptr = handle->cpu_data[cpu].page->map;
+	unsigned int flags;
 
 	/* FIXME: handle header page */
 	if (pevent->header_page_ts_size != 8) {
@@ -690,16 +697,39 @@ static int update_page_info(struct tracecmd_input *handle, int cpu)
 	ptr += 8;
 	switch (pevent->header_page_size_size) {
 	case 4:
-		handle->cpu_data[cpu].page_size = data2host4(pevent, ptr);
+		flags = data2host4(pevent, ptr);
+		ptr += 4;
 		break;
 	case 8:
-		handle->cpu_data[cpu].page_size = data2host8(pevent, ptr);
+		flags = (unsigned int)data2host8(pevent, ptr);
+		ptr += 8;
 		break;
 	default:
 		warning("bad long size");
 		return -1;
 	}
 
+	handle->cpu_data[cpu].page_size = flags & COMMIT_MASK;
+
+	if (flags & MISSING_EVENTS) {
+		breakpoint();
+		if (flags & MISSING_STORED) {
+			ptr += handle->cpu_data[cpu].page_size;
+			switch (pevent->header_page_size_size) {
+			case 4:
+				handle->cpu_data[cpu].page->lost_events =
+					data2host4(pevent, ptr);
+				break;
+			case 8:
+				handle->cpu_data[cpu].page->lost_events =
+					data2host8(pevent, ptr);
+				break;
+			}
+		} else
+			handle->cpu_data[cpu].page->lost_events = -1;
+	} else
+		handle->cpu_data[cpu].page->lost_events = 0;
+
 	handle->cpu_data[cpu].index = 0;
 
 	return 0;
@@ -1435,6 +1465,7 @@ tracecmd_peek_data(struct tracecmd_input *handle, int cpu)
 	void *ptr;
 	unsigned long long extend;
 	unsigned int type_len;
+	long long missed_events = 0;
 	int length;
 
 	if (index < 0)
@@ -1464,8 +1495,10 @@ tracecmd_peek_data(struct tracecmd_input *handle, int cpu)
 
 	ptr = page->map + index;
 
-	if (!index)
+	if (!index) {
+		missed_events = page->lost_events;
 		ptr = handle->cpu_data[cpu].page->map + pevent->header_page_data_offset;
+	}
 
 read_again:
 	index = calc_index(handle, ptr, cpu);
@@ -1520,6 +1553,7 @@ tracecmd_peek_data(struct tracecmd_input *handle, int cpu)
 	record->cpu = cpu;
 	record->data = ptr;
 	record->offset = handle->cpu_data[cpu].offset + index;
+	record->missed_events = missed_events;
 
 	ptr += length;
 

diff --git a/trace-read.c b/trace-read.c
@@ -462,6 +462,12 @@ static void show_data(struct tracecmd_input *handle,
 	test_save(record, cpu);
 
 	trace_seq_init(&s);
+	if (record->missed_events > 0)
+		trace_seq_printf(&s, "CPU:%d [%lld EVENTS DROPPED]\n",
+				 record->cpu, record->missed_events);
+	else if (record->missed_events < 0)
+		trace_seq_printf(&s, "CPU:%d [EVENTS DROPPED]\n",
+				 record->cpu);
 	pevent_print_event(pevent, &s, record);
 	trace_seq_do_printf(&s);