dump: Add UTC offset to Chrome trace format #2023
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namhyung
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Sep 29, 2025
cmds/dump.c
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| static bool offset_initialized = false; | ||
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| /* Initialize the UTC offset once if the option is enabled */ | ||
| if (chrome->opts && chrome->opts->with_utc_offset && !offset_initialized) { |
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I don't think chrome->opts can be NULL. Also I think we can just use utc_offset_ns == 0 if it's initialized or not.
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Thanks for your feedback!
I removed the --with-utc-offset flag as you recommended. Also, I fixed the issue regarding checking for chrome->opts and offset initialization.
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This patch applies the UTC offset to timestamps in Chrome trace output. When enabled, the timestamps represent actual UTC time rather than monotonic time, making it easier to correlate trace events with external time-based data or logs. The UTC offset information is already available in the trace metadata (added in commit fae85a8), and this patch leverages that data to adjust timestamps when the option is specified. Signed-off-by: Kaveh Shahedi <[email protected]>
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Description
This PR adds support for UTC-adjusted timestamps in Chrome trace format output. Before, when using
uftrace dump --chrome, the timestamps are based on monotonic clock values, which start from an arbitrary point (appearing as timestamps from 1970 when converted to dates). This makes it challenging to correlate trace events with actual wall-clock time (e.g., manually correlating with kernel traces from LTTng or perf).With this change, we can now get timestamps that represent actual UTC time. The implementation uses the existing UTC offset information already stored in uftrace metadata (in #1923).
Usage
Record a trace
Dump to a Chrome JSON file
[ { "ts":1759035568795552.450, "ph":"B", "pid":4003, "name":"main" }, { "ts":1759035568795561.123, "ph":"B", "pid":4003, "name":"sqlite3_sourceid" }, { "ts":1759035568795561.262, "ph":"E", "pid":4003, "name":"sqlite3_sourceid" }, { "ts":1759035568795857.122, "ph":"B", "pid":4003, "name":"cli_strncmp" }, { "ts":1759035568795857.745, "ph":"E", "pid":4003, "name":"cli_strncmp" }, { "ts":1759035568795858.157, "ph":"B", "pid":4003, "name":"main_init" }, ... ]