refactor: simplify allocation tracker lifecycle#543
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Use `_instance != nullptr` as the single source of truth for "tracking active", dropping the separate `track_allocations` atomic and the lazy `remaining_bytes_initialized` flag (TLS shrinks 48 -> 40 bytes). The per-thread sampling offset is now applied once in `init_tl_state` instead of on every first allocation. - Make `_instance` a `std::atomic<AllocationTracker *>` with acquire/release ordering and route all accesses through a `get_instance()` helper so publishing and tearing down the instance synchronize correctly with observing threads. - Initialize the starter thread's TLS before publishing `_instance` to avoid a window where other threads observe a non-null instance with half-initialized state. - Defer `pevent_munmap_event` to the next `allocation_tracking_init` (guarded by `mapfd != -1`) so in-flight hooks cannot race with teardown; add default initializers to `PEvent` to make the guard sound. - Call `restore_overrides()` in `allocation_profiling_stop` to pair with `setup_overrides()` on start.
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| void allocation_profiling_stop() { | ||
| if (g_state.allocation_profiling_started) { | ||
| restore_overrides(); |
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Good idea, restoring should improve performance for the user.
Document that ddprof_stop_profiling() does not drain in-flight allocation hooks, and that a stop/start sequence requires the caller to quiesce allocation activity to avoid racing with ring buffer re-init. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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What does this PR do?
Use
_instance != nullptras the single source of truth for "tracking active", dropping the separatetrack_allocationsatomic and the lazyremaining_bytes_initializedflag (TLS shrinks 48 -> 40 bytes). The per-thread sampling offset is now applied once ininit_tl_stateinstead of on every first allocation._instanceto avoid a window where other threads observe a non-null instance with half-initialized state.pevent_munmap_eventto the nextallocation_tracking_init(guarded bymapfd != -1) so in-flight hooks cannot race with teardown; add default initializers toPEventto make the guard sound.restore_overrides()inallocation_profiling_stopto pair withsetup_overrides()on start.Possibly fixes #541