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Alexey MilovidovandClaude Opus 4.8
3b3c99a08d
On macOS, `nstime_get` used `mach_absolute_time` (a monotonic uptime clock) because `JEMALLOC_HAVE_MACH_ABSOLUTE_TIME` was defined in the Darwin config headers, while the background thread's condition variable is created with the default clock (`CLOCK_REALTIME`): macOS has no `pthread_condattr_setclock`, and jemalloc only attempts to bind the condvar to a monotonic clock when `JEMALLOC_HAVE_CLOCK_MONOTONIC[_COARSE]` is defined (it is not, on Darwin). `background_thread_sleep` builds the `pthread_cond_timedwait` deadline from the `nstime` (uptime) clock and passes it to a `CLOCK_REALTIME` wait. The uptime value is decades behind the realtime epoch, so the deadline is always in the past and the wait returns `ETIMEDOUT` immediately - the background thread busy-spins a CPU core during the whole decay window instead of sleeping for `dirty_decay_ms`. This would replace the old `madvise` storm with a hot background-thread loop on exactly the allocation-churning workload that enabling `background_thread:true` was meant to speed up. Fix: undef `JEMALLOC_HAVE_MACH_ABSOLUTE_TIME` in the Darwin headers so `nstime_get` falls back to `gettimeofday` (`CLOCK_REALTIME`) - the same clock the condvar waits on - so the timed-wait deadline is honoured. This is the canonical clock for `pthread_cond_timedwait` on macOS. Linux and FreeBSD are unaffected (they use their own config headers). This is a prerequisite for `JEMALLOC_BACKGROUND_THREAD` to work correctly on macOS, enabled in the previous commits of this branch. See https://github.com/ClickHouse/ClickHouse/issues/108429 Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>