git/trace2.c, branch v2.36.2

trace2: add stats for fsync operations

2022-03-30T18:15:55Z

Add some global trace2 statistics for the number of fsyncs performed during the lifetime of a Git process. These stats are printed as part of trace2_cmd_exit_fl, which is presumably where we might want to print any other cross-cutting statistics. Signed-off-by: Neeraj Singh Signed-off-by: Junio C Hamano

C99: remove hardcoded-out !HAVE_VARIADIC_MACROS code

2022-02-22T03:14:19Z

Remove the "else" branches of the HAVE_VARIADIC_MACROS macro, which have been unconditionally omitted since 765dc168882 (git-compat-util: always enable variadic macros, 2021-01-28). Since were always omitted, anyone trying to use a compiler without variadic macro support to compile a git since version git v2.31.0 or later would have had a compilation error. 10 months across a few releases since then should have been enough time for anyone who cared to run into that and report the issue. In addition to that, for anyone unsetting HAVE_VARIADIC_MACROS we've been emitting extremely verbose warnings since at least ee4512ed481 (trace2: create new combined trace facility, 2019-02-22). That's because there is no such thing as a "region_enter_printf" or "region_leave_printf" format, so at least under GCC and Clang everything that includes trace.h (almost every file) emits a couple of warnings about that. There's a large benefit to being able to have a hard dependency rely on variadic macros, the code surrounding usage.c is hard to maintain if we need to write two implementations of everything, and by relying on "__FILE__" and "__LINE__" along with "__VA_ARGS__" we can in the future make error(), die() etc. log where they were called from. We've also recently merged d67fc4bf0ba (Merge branch 'bc/require-c99', 2021-12-10) which further cements our hard dependency on C99. So let's delete the fallback code, and update our CodingGuidelines to note that we depend on this. The added bullet-point starts with lower-case for consistency with other bullet-points in that section. The diff in "trace.h" is relatively hard to read, since we need to retain the existing API docs, which were comments on the code used if HAVE_VARIADIC_MACROS was not defined. Signed-off-by: Ævar Arnfjörð Bjarmason Signed-off-by: Junio C Hamano

trace2: add trace2_child_ready() to report on background children

2021-09-20T15:57:58Z

Create "child_ready" event to capture the state of a child process created in the background. When a child command is started a "child_start" event is generated in the Trace2 log. For normal synchronous children, a "child_exit" event is later generated when the child exits or is terminated. The two events include information, such as the "child_id" and "pid", to allow post analysis to match-up the command line and exit status. When a child is started in the background (and may outlive the parent process), it is not possible for the parent to emit a "child_exit" event. Create a new "child_ready" event to indicate whether the child was successfully started. Also include the "child_id" and "pid" to allow similar post processing. This will be used in a later commit with the new "start_bg_command()". Signed-off-by: Jeff Hostetler Signed-off-by: Junio C Hamano

tr2: log parent process name

2021-07-22T20:35:20Z

It can be useful to tell who invoked Git - was it invoked manually by a user via CLI or script? By an IDE? In some cases - like 'repo' tool - we can influence the source code and set the GIT_TRACE2_PARENT_SID environment variable from the caller process. In 'repo''s case, that parent SID is manipulated to include the string "repo", which means we can positively identify when Git was invoked by 'repo' tool. However, identifying parents that way requires both that we know which tools invoke Git and that we have the ability to modify the source code of those tools. It cannot scale to keep up with the various IDEs and wrappers which use Git, most of which we don't know about. Learning which tools and wrappers invoke Git, and how, would give us insight to decide where to improve Git's usability and performance. Unfortunately, there's no cross-platform reliable way to gather the name of the parent process. If procfs is present, we can use that; otherwise we will need to discover the name another way. However, the process ID should be sufficient to look up the process name on most platforms, so that code may be shareable. Git for Windows gathers similar information and logs it as a "data_json" event. However, since "data_json" has a variable format, it is difficult to parse effectively in some languages; instead, let's pursue a dedicated "cmd_ancestry" event to record information about the ancestry of the current process and a consistent, parseable way. Git for Windows also gathers information about more than one generation of parent. In Linux further ancestry info can be gathered with procfs, but it's unwieldy to do so. In the interest of later moving Git for Windows ancestry logging to the 'cmd_ancestry' event, and in the interest of later adding more ancestry to the Linux implementation - or of adding this functionality to other platforms which have an easier time walking the process tree - let's make 'cmd_ancestry' accept an array of parentage. Signed-off-by: Emily Shaffer Signed-off-by: Junio C Hamano

trace2: add a public function for getting the SID

2020-11-12T02:26:52Z

Add a public wrapper, trace2_session_id(), around tr2_sid_get(), which is intended to be private trace2 implementation. Signed-off-by: Josh Steadmon Signed-off-by: Junio C Hamano

trace2: teach Git to log environment variables

2020-03-23T20:14:53Z

Via trace2, Git can already log interesting config parameters (see the trace2_cmd_list_config() function). However, this can grant an incomplete picture because many config parameters also allow overrides via environment variables. To allow for more complete logs, we add a new trace2_cmd_list_env_vars() function and supporting implementation, modeled after the pre-existing config param logging implementation. Signed-off-by: Josh Steadmon Acked-by: Jeff Hostetler Signed-off-by: Junio C Hamano

Merge branch 'jh/trace2'

2019-05-13T14:50:35Z

A few embarrassing bugfixes. * jh/trace2: trace2: fix up a missing "leave" entry point trace2: fix incorrect function pointer check

Merge branch 'jh/trace2-sid-fix'

2019-05-13T14:50:31Z

Polishing of the new trace2 facility continues. The system-level configuration can specify site-wide trace2 settings, which can be overridden with per-user configuration and environment variables. * jh/trace2-sid-fix: trace2: fixup access problem on /etc/gitconfig in read_very_early_config trace2: update docs to describe system/global config settings trace2: make SIDs more unique trace2: clarify UTC datetime formatting trace2: report peak memory usage of the process trace2: use system/global config for default trace2 settings config: add read_very_early_config() trace2: find exec-dir before trace2 initialization trace2: add absolute elapsed time to start event trace2: refactor setting process starting time config: initialize opts structure in repo_read_config()

trace2: fix incorrect function pointer check

2019-04-26T02:44:00Z

Fix trace2_data_json_fl() to check for the presence of pfn_data_json_fl in its targets, rather than pfn_data_fl, which is not actually called. Signed-off-by: Josh Steadmon Signed-off-by: Junio C Hamano

trace2: report peak memory usage of the process

2019-04-16T04:37:07Z

Teach Windows version of git to report peak memory usage during exit() processing. Signed-off-by: Jeff Hostetler Signed-off-by: Junio C Hamano