* fix(lock): let waiters hear releases and let acquisition succeed past registered waiters
Same-key write contention scaled superlinearly with writer count: 8
concurrent conditional PUTs on one key cost ~340-460 ms, 16 cost ~700 ms,
32 cost ~5 s, against ~4 ms per uncontended write and ~10 ms actual lock
holds (measured via RUSTFS_OBJECT_LOCK_DIAG at 1 ms thresholds). Outcomes
were always correct; the cost was pure waiting.
Two coupled defects in fast_lock caused it:
1. The slow path's early retries slept without subscribing to anything.
notify_writer()/notify_readers() are gated on the waiter counters,
which a sleeper never increments, so a release during the backoff
woke nobody. The lock sat free while every loser slept out its full
backoff, and the ladder compounded: successive acquires landed at
the cumulative ladder offsets (10+20+40+80+100... ms).
2. try_acquire_exclusive demanded the entire packed state word be zero,
including the readers_waiting/writers_waiting counter bits. A lock
with registered waiters could be acquired by no one - including the
waiters themselves, each blocked by the others' registration - so
contended acquisition only succeeded in windows where every waiter
happened to be unregistered. This is also why (1) could not be fixed
by simply registering the sleepers: registration alone deadlocks
acquisition until the acquire deadline. try_acquire_shared already
masks correctly and preserves the counter bits in its CAS; the
exclusive path now mirrors it.
The fix: mask the acquisition CAS to ownership bits only (writer flag,
active readers), and turn the early-retry sleep into a notification wait
bounded by the same backoff, so a release wakes a waiter immediately
while the bound still protects against lost or stolen wakeups exactly as
NOTIFY_WAIT_CAP does for the post-retry wait.
With both changes, 8 concurrent same-key CAS writers resolve in 17-29 ms
(was 340-460 ms) and 32 resolve in 20-53 ms (was ~5 s), with per-racer
cost now decreasing in N. Outcomes remain exactly one winner, N-1
precondition failures, zero errors at every width. cargo test -p
rustfs-lock passes 113/113 at pristine-parity runtime, including
test_concurrent_write_lock_contention, which previously only passed
because sleepers were invisible to it.
* test(lock): pin both halves of the waiter-starvation fix
The fix commit touched only production files, so reverting either half
left the suite green: test_concurrent_write_lock_contention only waits
for five writers to finish and never asserts that acquisition happens
before the backoff ladder runs out.
Three tests, one per revert:
* exclusive_acquisition_ignores_registered_waiters (state.rs) - a free
lock with registered waiters must be acquirable, and the CAS must
preserve the counters. Fails against the all-zero `expected`.
* early_retry_registers_as_waiter (shard.rs) - a waiter in the
early-retry backoff must appear in the writer waiter count within the
~750ms early-retry phase, since notify_writer/notify_readers are gated
on those counters. Fails against a bare `sleep`, which registers
nowhere.
* contended_writers_drain_promptly_after_release (tests.rs) - 16 same-key
writers, all registered behind one holder, must drain within 1s of the
release rather than sit out their 5s acquire deadlines. Fails against
the all-zero `expected` end to end.
Wakeup latency is deliberately not asserted anywhere. NOTIFY_POOL is a
process-global of 128 Notify slots shared by every lock, so a waiter in
a concurrently-running test can consume another's notify_one and push it
to the end of its rung: a 24-key latency probe measured ~150us in
isolation and ~92ms - a full unexpired rung - alongside the existing
64-key missed-wakeup test. That is the stolen wakeup NOTIFY_WAIT_CAP
already exists to bound, and it makes any in-suite latency budget flaky.
cargo test -p rustfs-lock: 116/116.
Signed-off-by: Miguel Amador <miguel@amador.one>
---------
Signed-off-by: Miguel Amador <miguel@amador.one>
- Add lock timeout support and track acquisition time in lock state
- Improve lock conflict handling with detailed error messages
- Optimize lock reuse when already held by same owner
- Refactor lock state to store owner info and timeout duration
- Update all lock operations to handle new state structure
Signed-off-by: junxiang Mu <1948535941@qq.com>
Increase the size of the notification pool to reduce the thundering herd effect under high concurrency
Implement an adaptive timeout mechanism that dynamically adjusts based on system load and priority
Add a lock protection mechanism to prevent premature cleanup of active locks
Add lock acquisition methods for high-priority and critical-priority locks
Improve the cleanup strategy to be more conservative under high load
Add detailed debug logs to assist in diagnosing lock issues
Signed-off-by: junxiang Mu <1948535941@qq.com>
* Refactor: reimplement lock
Signed-off-by: junxiang Mu <1948535941@qq.com>
* Fix: fix test case failed
Signed-off-by: junxiang Mu <1948535941@qq.com>
* Improve: lock pref
Signed-off-by: junxiang Mu <1948535941@qq.com>
* fix(lock): Fix resource cleanup issue when batch lock acquisition fails
Ensure that the locks already acquired are properly released when batch lock acquisition fails to avoid memory leaks
Improve the lock protection mechanism to prevent double release issues
Add complete Apache license declarations to all files
Signed-off-by: junxiang Mu <1948535941@qq.com>
---------
Signed-off-by: junxiang Mu <1948535941@qq.com>
Miguel Amador