On Fri, Mar 15, 2019 at 10:38 AM Tzvetomir Stoyanov
<tstoyanov@xxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxx>
> ---
> include/trace-cmd/trace-cmd.h | 1 +
> lib/trace-cmd/trace-input.c | 119 +++++++++++++++++++++++++++++++++-
> 2 files changed, 118 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..714f01c 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_corr {
> + long long time;
> + long long offset;
> +};
ts_offset_corr is not a particularly descriptive name imo. Wdyt about
ts_offset_sample?
> +
> 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_corr *ts_corr;
> double ts2secs;
> char * cpustats;
> char * uname;
> @@ -1028,6 +1035,68 @@ 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_corr *min,
> + struct ts_offset_corr *max)
> +{
> + long long tscor = min->offset +
> + (((((long long)ts) - min->time)*
> + (max->offset-min->offset))/(max->time-min->time));
There's potential of dividing by zero here. Can we handle (drop?) such
invalid samples in tsync_offset_load() below?
> +
> + if (tscor < 0)
> + return ts - llabs(tscor);
> +
> + return ts + tscor;
> +
> +}
> +
> +static unsigned long long timestamp_correct(unsigned long long ts,
> + struct tracecmd_input *handle)
> +{
> + static int min = -1;
> + static int max = -1;
Caching in static variables here is not thread safe and might bite
users in the future when we transition this code to a library. How
about dropping caching here and use binary search below instead?
-- Slavi
> + int i;
> +
> + if (handle->ts_offset)
> + return ts + handle->ts_offset;
> + if (!handle->ts_corr_count || !handle->ts_corr)
> + return ts;
> +
> + /* We have only one offset, nothing to calc here */
> + if (handle->ts_corr_count == 1)
> + return ts + handle->ts_corr[0].offset;
> +
> + /* We have two offsets, 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 offsets */
> + /* check if current ts fits in the last found time frame */
> + if (min >= 0 && max >= 0 &&
> + ts >= handle->ts_corr[min].time &&
> + ts <= handle->ts_corr[max].time) {
> + return timestamp_correction_calc(ts, &handle->ts_corr[min],
> + &handle->ts_corr[max]);
> + }
> + min = -1;
> + max = -1;
> + for (i = 0; i < handle->ts_corr_count; i++) {
> + if (ts > handle->ts_corr[i].time)
> + min = i;
> + else if (ts <= handle->ts_corr[i].time) {
> + max = i;
> + break;
> + }
> + }
> + if (min >= 0 && max >= 0 && min != max &&
> + min < handle->ts_corr_count && max < handle->ts_corr_count)
> + return timestamp_correction_calc(ts, &handle->ts_corr[min],
> + &handle->ts_corr[max]);
> +
> + return ts;
> +}
> +
> /*
> * Page is mapped, now read in the page header info.
> */
> @@ -1049,7 +1118,7 @@ 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 +1845,7 @@ 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 +2170,34 @@ 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_corr *ts_a = (struct ts_offset_corr *)a;
> + struct ts_offset_corr *ts_b = (struct ts_offset_corr *)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;
> + 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_corr),
> + tsync_offset_cmp);
> +}
> +
> static int handle_options(struct tracecmd_input *handle)
> {
> long long offset;
> @@ -2111,6 +2208,7 @@ 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 +2253,23 @@ 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.
> + */
> + 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
>
|