[PATCH v7 8/9] trace-cmd: Implemented new option in trace.dat file: TRACECMD_OPTION_TIME_SHIFT

[Tzvetomir Stoyanov <tstoyanov@vmware.com>]

The TRACECMD_OPTION_TIME_SHIFT is used when synchronizing trace time stamps between
two trace.dat files. It contains multiple long long (time, offset) pairs, describing
time stamps _offset_, measured in the given local _time_. The content of the option
buffer is:
 first 4 bytes - integer, count of timestamp offsets
 long long array of size _count_, local time in which the offset is measured
 long long array of size _count_, offset of the time stamps

Signed-off-by: Tzvetomir Stoyanov <tstoyanov@vmware.com>
---
 include/trace-cmd/trace-cmd.h |   1 +
 lib/trace-cmd/trace-input.c   | 127 +++++++++++++++++++++++++++++++++-
 2 files changed, 126 insertions(+), 2 deletions(-)

diff --git a/include/trace-cmd/trace-cmd.h b/include/trace-cmd/trace-cmd.h
index f7c043a..5552396 100644
--- a/include/trace-cmd/trace-cmd.h
+++ b/include/trace-cmd/trace-cmd.h
@@ -82,6 +82,7 @@ enum {
 	TRACECMD_OPTION_HOOK,
 	TRACECMD_OPTION_OFFSET,
 	TRACECMD_OPTION_CPUCOUNT,
+	TRACECMD_OPTION_TIME_SHIFT,
 };
 
 enum {
diff --git a/lib/trace-cmd/trace-input.c b/lib/trace-cmd/trace-input.c
index 0a6e820..04f222d 100644
--- a/lib/trace-cmd/trace-input.c
+++ b/lib/trace-cmd/trace-input.c
@@ -75,6 +75,11 @@ struct input_buffer_instance {
 	size_t			offset;
 };
 
+struct ts_offset_sample {
+	long long	time;
+	long long	offset;
+};
+
 struct tracecmd_input {
 	struct tep_handle	*pevent;
 	struct tep_plugin_list	*plugin_list;
@@ -92,6 +97,8 @@ struct tracecmd_input {
 	bool			use_pipe;
 	struct cpu_data 	*cpu_data;
 	long long		ts_offset;
+	int			ts_corr_count;
+	struct ts_offset_sample	*ts_corr;
 	double			ts2secs;
 	char *			cpustats;
 	char *			uname;
@@ -1028,6 +1035,66 @@ static void free_next(struct tracecmd_input *handle, int cpu)
 	free_record(record);
 }
 
+static inline unsigned long long
+timestamp_correction_calc(unsigned long long ts, struct ts_offset_sample *min,
+			  struct ts_offset_sample *max)
+{
+	long long tscor = min->offset +
+			(((((long long)ts) - min->time)*
+			(max->offset-min->offset))/(max->time-min->time));
+
+	if (tscor < 0)
+		return ts - llabs(tscor);
+
+	return ts + tscor;
+
+}
+
+static unsigned long long timestamp_correct(unsigned long long ts,
+					    struct tracecmd_input *handle)
+{
+	int min, mid, max;
+
+	if (handle->ts_offset)
+		return ts + handle->ts_offset;
+	if (!handle->ts_corr_count || !handle->ts_corr)
+		return ts;
+
+	/* We have one sample, nothing to calc here */
+	if (handle->ts_corr_count == 1)
+		return ts + handle->ts_corr[0].offset;
+
+	/* We have two samples, nothing to search here */
+	if (handle->ts_corr_count == 2)
+		return timestamp_correction_calc(ts, &handle->ts_corr[0],
+						 &handle->ts_corr[1]);
+
+	/* We have more than two samples */
+	min = 0;
+	max = handle->ts_corr_count-1;
+	mid = (min + max)/2;
+	while (min <= max) {
+		if (ts >= handle->ts_corr[mid].time &&
+		    (mid == handle->ts_corr_count-1 ||
+		     ts < handle->ts_corr[mid+1].time))
+			break;
+		if (ts < handle->ts_corr[mid].time) {
+			if (mid == 0)
+				break;
+			min = mid-1;
+		} else if (ts >= handle->ts_corr[mid+1].time)
+			max = mid + 1;
+		mid = (min + max)/2;
+	}
+
+	if (mid >= handle->ts_corr_count-2)
+		return timestamp_correction_calc(ts, &handle->ts_corr[handle->ts_corr_count-2],
+						 &handle->ts_corr[handle->ts_corr_count-1]);
+
+	return timestamp_correction_calc(ts, &handle->ts_corr[mid],
+					 &handle->ts_corr[mid+1]);
+}
+
 /*
  * Page is mapped, now read in the page header info.
  */
@@ -1049,7 +1116,7 @@ static int update_page_info(struct tracecmd_input *handle, int cpu)
 		    kbuffer_subbuffer_size(kbuf));
 		return -1;
 	}
-	handle->cpu_data[cpu].timestamp = kbuffer_timestamp(kbuf) + handle->ts_offset;
+	handle->cpu_data[cpu].timestamp = timestamp_correct(kbuffer_timestamp(kbuf), handle);
 
 	if (handle->ts2secs)
 		handle->cpu_data[cpu].timestamp *= handle->ts2secs;
@@ -1776,7 +1843,7 @@ read_again:
 		goto read_again;
 	}
 
-	handle->cpu_data[cpu].timestamp = ts + handle->ts_offset;
+	handle->cpu_data[cpu].timestamp = timestamp_correct(ts, handle);
 
 	if (handle->ts2secs) {
 		handle->cpu_data[cpu].timestamp *= handle->ts2secs;
@@ -2101,6 +2168,42 @@ void tracecmd_set_ts2secs(struct tracecmd_input *handle,
 	handle->use_trace_clock = false;
 }
 
+static int tsync_offset_cmp(const void *a, const void *b)
+{
+	struct ts_offset_sample *ts_a = (struct ts_offset_sample *)a;
+	struct ts_offset_sample *ts_b = (struct ts_offset_sample *)b;
+
+	if (ts_a->time > ts_b->time)
+		return 1;
+	if (ts_a->time < ts_b->time)
+		return -1;
+	return 0;
+}
+
+static void tsync_offset_load(struct tracecmd_input *handle, char *buf)
+{
+	int i, j;
+	long long *buf8 = (long long *)buf;
+
+	for (i = 0; i < handle->ts_corr_count; i++) {
+		handle->ts_corr[i].time = tep_read_number(handle->pevent,
+							  buf8+i, 8);
+		handle->ts_corr[i].offset = tep_read_number(handle->pevent,
+						buf8+handle->ts_corr_count+i, 8);
+	}
+	qsort(handle->ts_corr,
+	      handle->ts_corr_count, sizeof(struct ts_offset_sample),
+	      tsync_offset_cmp);
+	/* Filter possible samples with equal time */
+	for (i = 0, j = 0; i < handle->ts_corr_count; i++) {
+		if (i == 0 ||
+		    handle->ts_corr[i].time != handle->ts_corr[i-1].time) {
+			handle->ts_corr[j++].time = handle->ts_corr[i].time;
+			handle->ts_corr[j++].offset = handle->ts_corr[i].offset;
+		}
+	}
+}
+
 static int handle_options(struct tracecmd_input *handle)
 {
 	long long offset;
@@ -2111,6 +2214,7 @@ static int handle_options(struct tracecmd_input *handle)
 	struct input_buffer_instance *buffer;
 	struct hook_list *hook;
 	char *buf;
+	int tsync;
 	int cpus;
 
 	for (;;) {
@@ -2155,6 +2259,25 @@ static int handle_options(struct tracecmd_input *handle)
 			offset = strtoll(buf, NULL, 0);
 			handle->ts_offset += offset;
 			break;
+		case TRACECMD_OPTION_TIME_SHIFT:
+			/*
+			 * int (4 bytes) count of timestamp offsets.
+			 * long long array of size [count] of times,
+			 *	when the offsets were calculated.
+			 * long long array of size [count] of timestamp offsets.
+			 */
+			if (handle->flags & TRACECMD_FL_IGNORE_DATE)
+				break;
+			handle->ts_corr_count = tep_read_number(handle->pevent,
+								buf, 4);
+			tsync = (sizeof(long long)*handle->ts_corr_count);
+			if (size != (4+(2*tsync)))
+				break;
+			handle->ts_corr = malloc(2*tsync);
+			if (!handle->ts_corr)
+				return -ENOMEM;
+			tsync_offset_load(handle, buf+4);
+			break;
 		case TRACECMD_OPTION_CPUSTAT:
 			buf[size-1] = '\n';
 			cpustats = realloc(cpustats, cpustats_size + size + 1);
-- 
2.20.1