git/trace2, branch v2.40.2

trace2: add global counter mechanism

2022-10-24T19:45:26Z

Add global counters mechanism to Trace2. The Trace2 counters mechanism adds the ability to create a set of global counter variables and an API to increment them efficiently. Counters can optionally report per-thread usage in addition to the sum across all threads. Counter events are emitted to the Trace2 logs when a thread exits and at process exit. Counters are an alternative to `data` and `data_json` events. Counters are useful when you want to measure something across the life of the process, when you don't want per-measurement events for performance reasons, when the data does not fit conveniently within a region, or when your control flow does not easily let you write the final total. For example, you might use this to report the number of calls to unzip() or the number of de-delta steps during a checkout. Signed-off-by: Jeff Hostetler Signed-off-by: Junio C Hamano

trace2: add stopwatch timers

2022-10-24T19:45:26Z

Add stopwatch timer mechanism to Trace2. Timers are an alternative to Trace2 Regions. Regions are useful for measuring the time spent in various computation phases, such as the time to read the index, time to scan for unstaged files, time to scan for untracked files, and etc. However, regions are not appropriate in all places. For example, during a checkout, it would be very inefficient to use regions to measure the total time spent inflating objects from the ODB from across the entire lifetime of the process; a per-unzip() region would flood the output and significantly slow the command; and some form of post-processing would be requried to compute the time spent in unzip(). Timers can be used to measure a series of timer intervals and emit a single summary event (at thread and/or process exit). Signed-off-by: Jeff Hostetler Signed-off-by: Junio C Hamano

trace2: convert ctx.thread_name from strbuf to pointer

2022-10-24T19:45:26Z

Convert the `tr2tls_thread_ctx.thread_name` field from a `strbuf` to a "const char*" pointer. The `thread_name` field is a constant string that is constructed when the context is created. Using a (non-const) `strbuf` structure for it caused some confusion in the past because it implied that someone could rename a thread after it was created. That usage was not intended. Change it to a const pointer to make the intent more clear. Signed-off-by: Jeff Hostetler Signed-off-by: Junio C Hamano

trace2: improve thread-name documentation in the thread-context

2022-10-24T19:45:25Z

Improve the documentation of the tr2tls_thread_ctx.thread_name field and its relation to the tr2tls_thread_ctx.thread_id field. Signed-off-by: Jeff Hostetler Signed-off-by: Junio C Hamano

trace2: rename the thread_name argument to trace2_thread_start

2022-10-24T19:45:25Z

Rename the `thread_name` argument in `tr2tls_create_self()` and `trace2_thread_start()` to be `thread_base_name` to make it clearer that the passed argument is a component used in the construction of the actual `struct tr2tls_thread_ctx.thread_name` variable. The base name will be used along with the thread id to create a unique thread name. This commit does not change how the `thread_name` field is allocated or stored within the `tr2tls_thread_ctx` structure. Signed-off-by: Jeff Hostetler Signed-off-by: Junio C Hamano

tr2tls: clarify TLS terminology

2022-10-24T19:45:25Z

Reduce or eliminate use of the term "TLS" in the Trace2 code. The term "TLS" has two popular meanings: "thread-local storage" and "transport layer security". In the Trace2 source, the term is associated with the former. There was concern on the mailing list about it refering to the latter. Update the source and documentation to eliminate the use of the "TLS" term or replace it with the phrase "thread-local storage" to reduce ambiguity. Signed-off-by: Jeff Hostetler Signed-off-by: Junio C Hamano

trace2: use size_t alloc,nr_open_regions in tr2tls_thread_ctx

2022-10-24T19:45:25Z

Use "size_t" rather than "int" for the "alloc" and "nr_open_regions" fields in the "tr2tls_thread_ctx". These are used by ALLOC_GROW(). Signed-off-by: Jeff Hostetler Signed-off-by: Junio C Hamano

tr2: shows scope unconditionally in addition to key-value pair

2022-08-12T04:05:00Z

When we specify GIT_TRACE2_CONFIG_PARAMS or trace2.configparams, trace2 will prints "interesting" config values to log. Sometimes, when a config set in multiple scope files, the following output looks like (the irrelevant fields are omitted here as "..."): ...| def_param | ... | core.multipackindex:false ...| def_param | ... | core.multipackindex:false ...| def_param | ... | core.multipackindex:false As the log shows, even each config in different scope is dumped, but we don't know which scope it comes from. Therefore, it's better to add the scope names as well to make them be more recognizable. For example, when execute: $ GIT_TRACE2_PERF=1 \ > GIT_TRACE2_CONFIG_PARAMS=core.multipackIndex \ > git rev-list --test-bitmap HEAD" The following is the ouput (the irrelevant fields are omitted here as "..."): Format normal: ... git.c:461 ... def_param scope:system core.multipackindex=false ... git.c:461 ... def_param scope:global core.multipackindex=false ... git.c:461 ... def_param scope:local core.multipackindex=false Format perf: ... | def_param | ... | scope:system | core.multipackindex:false ... | def_param | ... | scope:global | core.multipackindex:false ... | def_param | ... | scope:local | core.multipackindex:false Format event: {"event":"def_param", ... ,"scope":"system","param":"core.multipackindex","value":"false"} {"event":"def_param", ... ,"scope":"global","param":"core.multipackindex","value":"false"} {"event":"def_param", ... ,"scope":"local","param":"core.multipackindex","value":"false"} Signed-off-by: Teng Long Signed-off-by: Junio C Hamano

trace2: use designated initializers for "struct tr2_dst"

2022-02-24T23:58:55Z

Convert the "static struct tr2_dst" assignments in trace2/* to use designated initializers. I don't think it improves readability to include the explicit 0-ing out of the fd/initialized/need_close/too_many_files members, so let's have those be initialized implicitly by the compiler. Signed-off-by: Ævar Arnfjörð Bjarmason Signed-off-by: Junio C Hamano

trace2: use designated initializers for "struct tr2_tgt"

2022-02-24T23:58:31Z

As with the preceding commit, change another set of file-level struct assignments to use designated initializers. As before the "= NULL" assignments are redundant, but we're keeping them for self-documentation purposes. The comments left to explain the pre-image can now be removed in favor of working code that relays the same information to the reader. Signed-off-by: Ævar Arnfjörð Bjarmason Signed-off-by: Junio C Hamano