Fix the overly verbose trace2 logging added in 9a4987677d3 (trace2: add stats for fsync operations, 2022-03-30) (first released with v2.36.0). Since that change every single "git" command invocation has included these "data" events, even though we'll only make use of these with core.fsyncMethod=batch, and even then only have non-zero values if we're writing object data to disk. See c0f4752ed2f (core.fsyncmethod: batched disk flushes for loose-objects, 2022-04-04) for that feature. As we're needing to indent the trace2_data_intmax() lines let's introduce helper variables to ensure that our resulting lines (which were already too) don't exceed the recommendations of the CodingGuidelines. Doing that requires either wrapping them twice, or introducing short throwaway variable names, let's do the latter. The result was that e.g. "git version" would previously emit a total of 6 trace2 events with the GIT_TRACE2_EVENT target (version, start, cmd_ancestry, cmd_name, exit, atexit), but afterwards would emit 8. We'd emit 2 "data" events before the "exit" event. The reason we didn't catch this was that the trace2 unit tests added in a15860dca3f (trace2: t/helper/test-trace2, t0210.sh, t0211.sh, t0212.sh, 2019-02-22) would omit any "data" events that weren't the ones it cared about. Before this change to the C code 6/7 of our "t/t0212-trace2-event.sh" tests would fail if this change was applied to "t/t0212/parse_events.perl". Let's make the trace2 testing more strict, and further append any new events types we don't know about in "t/t0212/parse_events.perl". Since we only invoke the "test-tool trace2" there's no guarantee that we'll catch other overly verbose events in the future, but we'll at least notice if we start emitting new events that are issues every time we log anything with trace2's JSON target. We exclude the "data_json" event type, we'd otherwise would fail on both "win test" and "win+VS test" CI due to the logging added in 353d3d77f4f (trace2: collect Windows-specific process information, 2019-02-22). It looks like that logging should really be using trace2_cmd_ancestry() instead, which was introduced later in 2f732bf15e6 (tr2: log parent process name, 2021-07-21), but let's leave it for now. Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx> --- I think this re-roll addresses the concerns Junio brought up in: https://lore.kernel.org/git/xmqqh74byy19.fsf@gitster.g/; As to the larger question of: On Thu, Jun 23 2022, Junio C Hamano wrote: > I am not sure if it is a good solution in the longer term, but this > implementation may be a good-enough way to squelch the immediate > loudness issue. I think a better long-term solution in this case, per the initial feedback on the patch would be to have a generic facility to trace2 log how often we call a given syscall: https://lore.kernel.org/git/220330.86zgl7o8l8.gmgdl@xxxxxxxxxxxxxxxxxxx/ I.e. in most (all?) other cases our trace2 logging is logging git's "business logic", but in this case the logging is functionally the same as a more dumb interception of an arbitrary system call, and then having some generic "syscall stats" trace2 event. In this case such a generic logger would need to be a bit smarter than just a dumb wrapper, i.e. we'd need: fsync() != EINTR /* due to fsync_loop() */ sync_file_range() That still wouldn't be the same as the current logging if implemented correctly, but I think in a good way. E.g. now we'll log a failed fsync() the same as a successful one, as we increment the counter before seeing what the return value was. But anyway, as noted in the original thread Neeraj didn't have time to look into that, neither do I, and the patch is now a part of git. So let's solve the immediate issue of verbose logging, and leave any other improvements for the future. Range-diff against v1: 1: df87e515efd ! 1: a1fc37de947 trace2: don't include "fsync" events in all trace2 logs @@ Commit message we're writing object data to disk. See c0f4752ed2f (core.fsyncmethod: batched disk flushes for loose-objects, 2022-04-04) for that feature. + As we're needing to indent the trace2_data_intmax() lines let's + introduce helper variables to ensure that our resulting lines (which + were already too) don't exceed the recommendations of the + CodingGuidelines. Doing that requires either wrapping them twice, or + introducing short throwaway variable names, let's do the latter. + The result was that e.g. "git version" would previously emit a total of 6 trace2 events with the GIT_TRACE2_EVENT target (version, start, cmd_ancestry, cmd_name, exit, atexit), but afterwards would emit @@ t/t0212/parse_events.perl + } + + elsif ($event eq 'data_json') { -+ # Ignore due to compat/win32/trace2_win32_process_info.c ++ # NEEDSWORK: Ignore due to ++ # compat/win32/trace2_win32_process_info.c, which should log a ++ # "cmd_ancestry" event instead. + } + + else { @@ wrapper.c: int git_fsync(int fd, enum fsync_action action) void trace_git_fsync_stats(void) { -+ if (!count_fsync_writeout_only && !count_fsync_hardware_flush) -+ return; +- trace2_data_intmax("fsync", the_repository, "fsync/writeout-only", count_fsync_writeout_only); +- trace2_data_intmax("fsync", the_repository, "fsync/hardware-flush", count_fsync_hardware_flush); ++ const struct repository *r = the_repository; ++ const intmax_t cfwo = count_fsync_writeout_only; ++ const intmax_t cfhf = count_fsync_hardware_flush; + - trace2_data_intmax("fsync", the_repository, "fsync/writeout-only", count_fsync_writeout_only); - trace2_data_intmax("fsync", the_repository, "fsync/hardware-flush", count_fsync_hardware_flush); ++ if (cfwo) ++ trace2_data_intmax("fsync", r, "fsync/writeout-only", cfwo); ++ if (cfhf) ++ trace2_data_intmax("fsync", r, "fsync/hardware-flush", cfhf); } + + static int warn_if_unremovable(const char *op, const char *file, int rc) t/t0212/parse_events.perl | 19 +++++++++++++------ wrapper.c | 10 ++++++++-- 2 files changed, 21 insertions(+), 8 deletions(-) diff --git a/t/t0212/parse_events.perl b/t/t0212/parse_events.perl index b6408560c0c..30a9f51e9f1 100644 --- a/t/t0212/parse_events.perl +++ b/t/t0212/parse_events.perl @@ -216,12 +216,19 @@ elsif ($event eq 'data') { my $cat = $line->{'category'}; - if ($cat eq 'test_category') { - - my $key = $line->{'key'}; - my $value = $line->{'value'}; - $processes->{$sid}->{'data'}->{$cat}->{$key} = $value; - } + my $key = $line->{'key'}; + my $value = $line->{'value'}; + $processes->{$sid}->{'data'}->{$cat}->{$key} = $value; + } + + elsif ($event eq 'data_json') { + # NEEDSWORK: Ignore due to + # compat/win32/trace2_win32_process_info.c, which should log a + # "cmd_ancestry" event instead. + } + + else { + push @{$processes->{$sid}->{$event}} => $line->{value}; } # This trace2 target does not emit 'printf' events. diff --git a/wrapper.c b/wrapper.c index 1c3c970080b..67727f95411 100644 --- a/wrapper.c +++ b/wrapper.c @@ -618,8 +618,14 @@ int git_fsync(int fd, enum fsync_action action) void trace_git_fsync_stats(void) { - trace2_data_intmax("fsync", the_repository, "fsync/writeout-only", count_fsync_writeout_only); - trace2_data_intmax("fsync", the_repository, "fsync/hardware-flush", count_fsync_hardware_flush); + const struct repository *r = the_repository; + const intmax_t cfwo = count_fsync_writeout_only; + const intmax_t cfhf = count_fsync_hardware_flush; + + if (cfwo) + trace2_data_intmax("fsync", r, "fsync/writeout-only", cfwo); + if (cfhf) + trace2_data_intmax("fsync", r, "fsync/hardware-flush", cfhf); } static int warn_if_unremovable(const char *op, const char *file, int rc) -- 2.37.0.880.gf07d56b18ba
