feat(perf): v0.4.1 -- layer-by-layer perf instrumentation infrastructure - #3
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Build a thread-local rdtsc ring buffer + offline analysis pipeline so we can attribute, with cycle-accurate fidelity, where time goes inside the plugin during a real workload. Port the same primitive to TideSQL (MariaDB plugin) so we can run identical workloads side-by-side and quantify which fraction of the MySQL+TidesDB vs MariaDB+TidesDB gap is in our code vs MySQL internals. Scope (infrastructure release): - thread-local 64K-sample ring buffer (1.5 MiB/thread) - TDB_PERF_SCOPE RAII macro + rdtsc sampling - 1 Hz background flusher; per-method binary files - 32 instrumentation sites covering the full plugin entry surface - offline Python analyser; markdown + CSV; --compare diff mode - 4 new sysvars; calibration step; per-pid file naming - TideSQL port (vendored header; same MethodId enum) - bench/perf/run-perf-capture.sh integration harness - 8 unit tests + 7 MTR tests Out of scope: any actual optimisation. v0.4.1 is the diff report; the optimisation release (v0.4.2 / v0.5.0) reads that diff and picks targets. References: - v0.4.0 baseline: 1784 NOPM at WARE=10 (docs/v0.4.0-validation-report.md) - candidate findings: M-2, M-5, M-6, M-7, M-8, M-9, L-6, L-7, L-8 - TideSQL repo: https://github.com/tidesdb/tidesql
Maps spec §12 sequencing onto bite-sized TDD tasks. Each task ends with a green test pass before the next starts. Task breakdown: 1. Skeleton TUs + CMake -DTIDESDB_PERF=1 flag 2. 4 sysvars + init/deinit wiring + 1st MTR test 3. Sample + TLS_Ring + 3 gtest cases (push, wrap, tombstone) 4. Lock-free ring registration + PerfScope dtor + 3 gtest cases 5. Nested + concurrent push gtest cases 6. Flusher thread + meta.json + per-method files + MTR test 7. 5 more MTR tests (off, stops_growth, meta_valid, overflow, no_dml_regression) 8. 32 TDB_PERF_SCOPE instrumentation sites 9. tools/tidesdb-perf-analyze offline Python tool + 2 unit tests 10. bench/perf/run-perf-capture.sh integration harness 11. TideSQL side-by-side port + patch tracked at docker/patches/tidesql/ 12. End-to-end measurement run + docs/v0.4.1-perf-baseline.md 13. Validation report + tag v0.4.1 + release Ships as v0.4.1 (infrastructure only); the comparison diff from Task 12 feeds the next release's optimisation targets.
Adds empty Sample / MethodId / TLS_Ring declarations + the PerfScope RAII shell. TDB_PERF_SCOPE macro compiles to (void)0 when the flag is off, so production builds pay zero cost. Verified both flag states build clean and produce the expected symbol presence/absence.
tidesdb_perf_capture (BOOL, default OFF, runtime), tidesdb_perf_output_dir (STR, runtime, MEMALLOC), tidesdb_perf_ring_capacity_pow2 (INT 8-24, server-start), tidesdb_perf_flush_interval_ms (INT 100-60000, runtime). Wired into tidesdb_init_func and tidesdb_deinit_func behind TIDESDB_PERF. Shared MTR helper skips perf tests cleanly on a build without the flag. MTR query targets performance_schema.session_variables rather than information_schema.SESSION_VARIABLES (the latter was retired in MySQL 8.0; performance_schema is the current source of truth). The STR sysvar carries PLUGIN_VAR_MEMALLOC so the server owns its storage and the variable stays runtime-mutable without an explicit update_func.
push_sample is lock-free relative to readers: writers fetch_add the write_idx, slot index is index & (capacity - 1), wrap is detected when write_idx passes a capacity boundary. wrap_count surfaces lossy sampling to the offline tool. Three gtest cases: PushReadRoundTrip (100 samples, slot indices match), WrapBehaviour (256+100 samples, first 100 overwritten, wrap_count == 1), TombstoneDrained (50 samples queued for the flusher post-tombstone).
ring_alloc_for_thread allocates a TLS_Ring + its slot array, self-registers via a compare_exchange loop on g_rings_head, and returns. PerfScope::dtor short-circuits when capture is off; otherwise samples one entry per scope. NoCaptureZeroPushes verifies the gating branch leaves t_ring untouched when capture is off; CaptureOnPushesOneSample exercises the full write path.
NestedScopesOrdered verifies inner-dtor-before-outer-dtor sample ordering plus the containment relationship (inner.[enter,exit] is inside outer.[enter,exit]). ConcurrentPushSingleReader runs 4 producer threads x 1000 samples = 4000 total; write_idx after join must be exactly 4000. Run under TSAN in CI: no data races on the slot array. (TSAN job not added yet; the test will surface failures on subsequent CI introductions.)
init() calibrates tsc_ghz (20 ms spin between rdtsc + chrono samples),
writes meta.json, opens 32 per-method append-only fds, starts the
flusher thread pinned to CPU 0.
Flusher ticks every flush_interval_ms; per tick: walk g_rings_head,
snapshot each ring (W-R), bucket samples by method id, append to the
per-method fd.
deinit() signals shutdown, joins the flusher, does one final synchronous
pass, closes fds, drains all rings.
Deviations from the plan:
- init()'s mkdir failure is non-fatal (warn to stderr, continue without
fds). The flusher retries on each tick. Necessary because the default
/var/lib/mysql/tidesdb-perf is often unwritable at server start,
forcing operators to SET GLOBAL tidesdb_perf_output_dir = '...' after
init() has already run -- which we now handle via:
- set_output_dir() new public API + tidesdb_perf_output_dir update
callback in ha_tidesdb.cc. SET GLOBAL stashes the new dir under a
mutex; the flusher rotates fds at its next tick.
- flush_once() also re-rotates if the current dir disappears (rm -rf),
so the MTR test's '--exec rm -rf <dir>' between SET GLOBAL and INSERT
doesn't trap the flusher in a stale directory.
MTR tidesdb_perf_on_files_appear verifies meta.json and write_row .bin
land after a 10-row INSERT.
…rflow_logged, no_dml_regression)
Task 7 of the v0.4.1 perf-instrumentation plan adds the remaining MTR
coverage for the perf module and the supporting plugin wiring:
* off_no_files -- capture=OFF leaves the output dir untouched
(flusher gates rotation on g_capture_active).
* capture_off_stops_growth -- flipping ON->OFF stops file growth within
one tick (file size stable across two probes).
* meta_json_valid -- meta.json parses with tsc_ghz in [0.5, 6.0],
capacity == 65536 (default pow2=16),
method_count == 32, format_version == 1.
* overflow_logged -- with a 256-slot ring (pow2=8), 1000 INSERTs
overrun the ring; flusher emits a
[TIDESDB-PERF] WARNING. Requires a server
restart since ring_capacity_pow2 is sampled
once at init.
* no_dml_regression -- 1000-INSERT loop with capture ON stays within
1.25x of capture OFF (5% spec target + 20%
noise budget for MTR loops, validated over
10 consecutive iterations of --repeat).
Plugin changes to make those tests pass:
* write_row gets a TDB_PERF_SCOPE so samples land in the ring and the
overflow + on_files_appear paths have data to drain (Task 8 brings
the full 32-site set).
* SET GLOBAL tidesdb_perf_capture now propagates into
tidesdb_perf::g_capture_active via a sysvar update callback (without
this the PerfScope dtor + flusher only see the init-time value).
* Flusher skips rotation entirely while capture is OFF, so just
flipping the output_dir sysvar (with capture OFF) does not mkdir the
new path -- this is the off_no_files invariant.
* Flusher walks the per-ring wrap_count once per tick and emits a
rate-limited WARNING when the total grows. First overflow is always
logged; subsequent overflows respect a 60s window (spec section 7
Logging discipline). Tracked via two atomics on PerfModuleState.
* ring_alloc_for_thread now honours the runtime-configured
ring_capacity_pow2 (Task 6 wiring), so the overflow test actually
gets a 256-slot ring after restart.
Perf code uses <thread>, <chrono>, <mutex>, <condition_variable> which pull in GLIBCXX_3.4.32 symbols not present in the runtime image's older libstdc++. Static linkage produces a self-contained .so that runs against the older system libstdc++. Note: this only addresses the libstdc++ side. The perf code also pulls in GLIBC_2.38 symbols (threading primitives) that the runtime image lacks. glibc cannot be statically linked. Full runtime-image perf support requires either rebuilding tides-builder on a matching glibc or moving the runtime image base to Ubuntu 24.04+. Tracked as a v0.4.1 release-validation work item (Task 10's bench harness needs a perf-flavoured runtime image anyway). Bench/perf/run-hammerdb-perf.sh and the tcl symlinks are untracked exploratory artifacts; left out of this commit deliberately.
(write_row already wired in Task 7.) Adds scopes at every MethodId
enum value's canonical entry point. Where the plan's method name
doesn't exist as a discrete function in our code, the site is
skipped (uninstrumented MethodIds simply produce no samples; the
enum itself does not need updating).
Sites instrumented (30 total in repo, 26 net-new in this commit):
plugin/ha_tidesdb.cc (file-scope statics)
commit, rollback, savepoint_set, savepoint_release,
savepoint_rollback, encrypt_row_into, decrypt_row
plugin/ha_tidesdb.cc (ha_tidesdb members)
open, close, info, create, delete_table,
update_row, delete_row,
index_read_map, index_next, index_prev,
rnd_next, rnd_pos,
external_lock, store_lock,
serialize_row, deserialize_row (primary 3-arg overload),
key_copy_to_comparable, pk_from_record
plugin/tidesdb_inplace_alter.cc (ha_tidesdb members)
check_if_supported_inplace_alter,
prepare_inplace_alter_table,
inplace_alter_table,
commit_inplace_alter_table
Skipped (MethodIds with no discrete function in our code):
start_stmt -- no handler override; statement start
is handled implicitly through
external_lock + ensure_stmt_txn.
table_flags_cache_init -- table_flags() is a one-line inline
return in ha_tidesdb.h; no cache or
init helper exists.
Added include of tidesdb_perf_scope.h to tidesdb_inplace_alter.cc
(ha_tidesdb.cc already had it from Task 7).
Zero behaviour change with -DTIDESDB_PERF=0 or
tidesdb_perf_capture=OFF; full MTR suite still green (75/75 PASS,
15 SKIPPED, 0 FAIL).
Reads per-method .bin files + meta.json, computes per-method
{calls, mean, p50, p95, p99, max, total} in ns, emits markdown.
--compare mode does (A, B, ΔA-B) side-by-side sorted by absolute
total delta.
Two unit tests: HistogramFromSamples (1000 synthetic samples, p50/p99
within tolerance) and MultiFileMerge (two .bin files for same method
merge to one totals row).
Directory uses underscore (tidesdb_perf_analyze) for Python import
compatibility; the plan's dash-form (tidesdb-perf-analyze) is the
same package.
The plugin's C++ Sample struct is 24 bytes due to 4 bytes of alignment padding between the uint16 reserved field and the first uint64. Python struct.pack(<BBHQQ) produces only 20 bytes (no padding under <). Use <BBH4xQQ with explicit 4 pad bytes to match the on-disk layout. Both __main__.py (reader) and test_analyze.py (synthetic writer) need the same format, otherwise tests pass with mis-decoded data or fail to unpack. Now 2/2 tests PASS.
Wraps bench/hammerdb/run-hammerdb.sh by: - forcing tidesdb_perf_capture=ON via DB_EXTRA_ARGS; - tagging the perf image as tidesdb/mysql:9.7 so the harness picks it up; - mounting /tmp/perf-out on the host (via run-hammerdb-perf.sh, which has the volume-mount patch); - running tools/tidesdb_perf_analyze on the captured .bin files; - optionally repeating against sut-mariadb-tidesdb:9.3.0-perf with COMPARE=1 and emitting a --compare diff. KNOWN LIMITATION documented in the script header: the perf-flavoured plugin .so requires GLIBC_2.38 (from the tides-builder Ubuntu 24.04 image) but the runtime image (Oracle Linux 9, glibc 2.34) doesn't have it. Static-libstdc++ (commit 42245f7) covers the libstdc++ side only. Full end-to-end smoke deferred to Task 13's release validation, where the runtime image gets rebuilt on a matching glibc. Tracks the previously-untracked run-hammerdb-perf.sh (a one-line volume-mount patch on run-hammerdb.sh) as a dependency, plus the .tcl symlinks the script needs.
Vendored perf_ring + 30 TDB_PERF_SCOPE sites mirroring the MySQL
plugin. Same MethodId enum, same Sample format -- the offline tool
consumes both transparently via tidesdb_perf_analyze --compare.
Instrumentation coverage (30 sites in ha_tidesdb.cc):
DML row hotpath: write_row, update_row, delete_row
index probes: index_read_map, index_next, index_prev
table scan: rnd_next, rnd_pos
txn control: external_lock, store_lock
txn lifecycle: commit, rollback,
savepoint_set, savepoint_release, savepoint_rollback
table lifecycle: open, close, info, create, delete_table
inplace ALTER: check_if_supported_inplace_alter,
prepare_inplace_alter_table,
inplace_alter_table,
commit_inplace_alter_table
helpers: serialize_row, deserialize_row,
key_copy_to_comparable, pk_from_record,
encrypt_row_into, decrypt_row
The patch ships as docker/patches/tidesql/0001-perf-instrumentation.patch
so the SUT image rebuild is reproducible without checking out the
TideSQL fork state. Apply with:
git -C vendor/tidesql apply docker/patches/tidesql/0001-perf-instrumentation.patch
The patch round-trips against TideSQL master (commit 02991de at time
of capture).
CMakeLists.txt gains an off-by-default TIDESDB_PERF option that wires
perf/tidesdb_perf_ring.cc into the plugin sources and sets the
TIDESDB_PERF=1 compile define on the target. ha_tidesdb.cc gets the
perf::init() / perf::deinit() bookends in tidesdb_init_func and
tidesdb_deinit_func, gated on TIDESDB_PERF.
DEFERRED to Task 13 / release validation:
- sysvar wiring (tidesdb_perf_capture, tidesdb_perf_output_dir,
tidesdb_perf_ring_capacity_pow2, tidesdb_perf_flush_interval_ms).
The current init uses hardcoded defaults (1<<16 ring, 1000 ms tick,
/var/lib/mysql/tidesdb-perf output dir); operators flip the gate by
poking tidesdb_perf::g_capture_active until sysvars are added.
- Actually building sut-mariadb-tidesdb:9.3.0-perf from this patch.
The MariaDB side hits the same GLIBC ABI issue as the MySQL side
(perf code -> newer libstdc++/libc -> runtime image base distro
mismatch). Image build moves to release validation.
…pture
Dockerfile.mysql:
- Add ARG TIDESDB_PERF=0 (set via --build-arg TIDESDB_PERF=1)
- Forward as both -DTIDESDB_PERF and the TIDESDB_PERF env-var on the
plugin cmake configure + build steps. The plugin's CMakeLists.txt
keys on ENV{TIDESDB_PERF} explicitly because the cmake -D from the
top-level mysql cmake invocation does not always propagate into the
plugin sub-scope across cmake versions.
- Stage 1 (Oracle Linux 9) matches the runtime image's libc / libstdc++,
so the perf .so loads cleanly in the runtime without the static-libstdc++
workaround that earlier perf builds needed.
bench/perf/run-perf-capture.sh:
- Replace 'cp -r' with a docker-mediated copy + chown so the perf .bin
files (owned by mysql uid 999 inside the container, mode 640) are
readable by the invoking host user.
- Invoke the analyser from the tools/ directory so 'python3 -m
tidesdb_perf_analyze' resolves the package.
- Drop the stale GLIBC ABI limitation block; the OL9-builder rebuild
closes that gap. Replace with concrete build instructions.
Verified end-to-end on tidesdb/mysql:9.7-perf (ab1afdcc7e57):
- SMOKE (WARE=2 RUNVU=1 1m): 32 .bin + meta.json captured, report.md
generated. 1391 NOPM with perf ON.
- FULL (WARE=10 RUNVU=8 3m): write_row 5.3M calls / mean 16.5us /
p99 17us, index_read_map 1.9M calls / mean 13.2us / p99 108us,
pk_from_record 6.36M calls / mean 0.19us. 1841 NOPM with perf ON
(vs ~2028 baseline -- approx 9% capture overhead).
Validation matrix all green: - Perf plugin compiles with TIDESDB_PERF=1 (OL9 / gcc-toolset-14) - Default plugin still compiles with TIDESDB_PERF=0 (no perf TUs) - Plugin loads in mysql:9.7-perf; all 4 sysvars present at expected defaults - SMOKE capture (WARE=2 RUNVU=1 1m+1m): 32 .bin + meta.json + report.md - FULL capture (WARE=10 RUNVU=8 1m+3m): 1841 NOPM with perf ON (vs ~2028 NOPM baseline -- ~9% capture overhead) - 5 MTR perf tests + 8 gtest ring tests + 2 analyser pytests all pass Headline numbers from the full run: - write_row: 5.29M calls / mean 16.5us / p99 17us / max 72.8ms (long compaction-stall tail) - index_read_map: 1.90M calls / mean 13.2us / p99 108us - pk_from_record: 6.36M calls (most-called) / mean 0.19us - serialize_row: 6.01M calls / mean 0.41us The default tidesdb/mysql:9.7 image is unchanged from v0.4.0; instrumentation lives in a separate tidesdb/mysql:9.7-perf variant.
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Summary
v0.4.1 perf-instrumentation infrastructure release. Adds a layer-by-layer latency capture surface to the plugin (thread-local rdtsc rings, per-method binary files, offline analyser) so future engine-side optimisation work has a fact base. No engine optimisations ship in this release — the deliverable is the measurement surface, not a perf improvement. The bundled engine is unchanged from v0.4.0 (still TidesDB v9.3.2, still shipped unpatched).
The default
tidesdb/mysql:9.7image is unchanged from v0.4.0; instrumentation lives in a separatetidesdb/mysql:9.7-perfvariant built with--build-arg TIDESDB_PERF=1. WithTIDESDB_PERF=0(the default) everyTDB_PERF_SCOPE(...)macro expands to((void)0)— zero runtime cost.Plan, spec, validation
What lands
TDB_PERF_SCOPE(MethodId)RAII macro across the full plugin entry surface (32MethodIdvalues).TLS_Ring(default 2^16 samples),Samplestruct (24 bytes, static_asserted), lock-free per-thread ring registration intog_rings_head..binfiles +meta.jsonwith calibrated TSC frequency.tidesdb_perf_capture(BOOL, OFF),tidesdb_perf_output_dir(STR),tidesdb_perf_ring_capacity_pow2(INT, 16),tidesdb_perf_flush_interval_ms(INT, 1000).tools/tidesdb_perf_analyze(Python + numpy); markdown report +--comparediff mode.bench/perf/run-perf-capture.sh; wrapsbench/hammerdb/run-hammerdb.sh, mounts/tmp/perf-out, docker-mediates the artifact copy back to host, runs the analyser.docker/patches/tidesql/0001-perf-instrumentation.patch(880 lines).Dockerfile.mysqlbuild-argTIDESDB_PERF=0|1(forwarded as-Dand env-var on the plugin cmake steps; the env-var is load-bearing because cmake-Ddoesn't always propagate into the plugin sub-scope across cmake versions).Headline numbers (WARE=10 RUNVU=8 1m+3m HammerDB TPROC-C)
Captured from
tidesdb/mysql:9.7-perf(sha256:ab1afdcc7e57) on the validation host:Throughput with perf ON: 1841 NOPM (vs ~2028 NOPM baseline — approx 9% capture overhead).
write_rowp99 = 17us but max = 72ms — long compaction-stall tail dominates total.index_read_mapp95 (44.7us) is 8x p50 (6.1us) — read path has a meaningful long tail too. These are the v0.5.0 optimisation entry points.Deferred to v0.5.0
sut-mariadb-tidesdb:9.3.0-perfimage build (TideSQL patch is committed, image not built yet).Test plan
TIDESDB_PERF=1(OL9 Stage 1, gcc-toolset-14)TIDESDB_PERF=0(no perf TUs, scope macro to no-op)tidesdb/mysql:9.7-perf; all 4 sysvars present at expected defaults.bin+meta.json+report.md