compositor: Implement JSON-timeline logging

Graphics / Wayland / Weston - Pekka Paalanen [collabora.co.uk] - 8 December 2014 07:02 UTC

Logging is activated and deactivated with the debug key binding 't'. When activated, it creates a new log file, where it records the events. The log file contains events and detailed object information entries in JSON format, and is meant to be parsed in sequence from beginning to the end.

The emitted events are mostly related to the output repaint cycle, like when repaint begins, is submitted to GPU, and when it completes on a
vblank. This is recorded per-output. Also some per-surface events are recorded, including when surface damage is flushed.

To reduce the log size, events refer to objects like outputs and surfaces by id numbers. Detailed object information is emitted only as needed: on the first object occurrence, and afterwards only if weston_timeline_object::force_refresh asks for it.

The detailed information for surfaces includes the string returned by weston_surface::get_label. Therefore it is important to set weston_timeline_object::force_refresh = 1 whenever the string would change, so that the new details get recorded.

A rudimentary parser and SVG generator can be found at: https://github.com/ppaalanen/wesgr

The timeline logs can answer questions including:- How does the compositor repaint cycle work timing-wise?- When was the vblank deadline missed?- What is the latency from surface commit to showing the new content on screen?- How long does it take to process the scenegraph?

v2: weston_surface::get_description renamed to get_label.
v3: reafctor a bit into fprint_quoted_string().

b502654 compositor: Implement JSON-timeline logging
Makefile.am | 4 +
desktop-shell/shell.c | 28 +++--
src/compositor.c | 40 +++++++
src/compositor.h | 5 +
src/timeline-object.h | 52 +++++++++
src/timeline.c | 294 +++++++++++++++++++++++++++++++++++++++++++++++++
src/timeline.h | 62 +++++++++++
7 files changed, 476 insertions(+), 9 deletions(-)

Upstream: cgit.freedesktop.org

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