WIP: trace2: a new trace facility

This patch series contains a new trace2 facility that hopefully addresses the recent trace- and structured-logging-related discussions. The intent is to eventually replace the existing trace_ routines (or to route them to the new trace2_ routines) as time permits.

This draft adds new trace2_ calls and leaves most of the original trace_ calls in place. Subsequent drafts will address this.

This version should be considered a replacement for my earlier structured logging patch series [1].

It addresses Jonathan Nieder's, Ben Peart's, Peff's, and Junio's comments [2,3,4,5] about merging the existing tracing routines, ease of use, progressive logging rather than logging at the end of the program, hiding all JSON details inside the trace2_ routines, and leaving an opening for additional formats (protobuf or whatever).

It also adds a nested performance tracing feature similar to Duy's suggestion in [6]. This version adds per-thread nesting and marks each event with a thread name.

[1]
https://public-inbox.org/git/[email protected]/
[2]
https://public-inbox.org/git/[email protected]/
[3]
https://public-inbox.org/git/[email protected]/
[4]
https://public-inbox.org/git/[email protected]/
[5] https://public-inbox.org/git/[email protected]/
[6] https://public-inbox.org/git/[email protected]/

Cc: [email protected]: [email protected]: [email protected]:
[email protected]: [email protected]

Jeff Hostetler (8):
trace2: create new combined trace facility
trace2: add trace2 to main
trace2: demonstrate trace2 regions in wt-status
trace2: demonstrate trace2 child process classification
trace2: demonstrate instrumenting do_read_index
trace2: demonstrate instrumenting threaded preload_index
trace2: demonstrate setting sub-command parameter in checkout
trace2: demonstrate use of regions in read_directory_recursive

 Makefile           |    1 +
 builtin/checkout.c |    5 +
 cache.h            |    1 +
 compat/mingw.h     |    3 +-
 dir.c              |    3 +
 editor.c           |    1 +
 git-compat-util.h  |    7 +
 git.c              |    9 +-
 pager.c            |    1 +
 preload-index.c    |   10 +
 read-cache.c       |    6 +
 repository.c       |    2 +
 run-command.c      |    8 +-
 run-command.h      |    5 +
 sub-process.c      |    1 +
 trace2.c           | 1592 ++++++++++++++++++++++++++++++++++++++++++++
 trace2.h           |  214 ++++++
 usage.c            |    5 +
 wt-status.c        |   14 +-
 19 files changed, 1882 insertions(+), 6 deletions(-)
 create mode 100644 trace2.c
 create mode 100644 trace2.h

base-commit: 2f743933341f276111103550fbf383a34dfcfd38
Published-As: https://github.com/gitgitgadget/git/releases/tags/pr-29%2Fjeffhostetler%2Fml-trace2-v0-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-29/jeffhostetler/ml-trace2-v0-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/29

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