Adaptive Lock Probes
Adaptive locks enforce mutual exclusion to a critical section, and may be acquired in
most contexts in the kernel. Because adaptive locks have few context restrictions, they
comprise the vast majority of synchronization primitives in the Solaris kernel. These locks
are adaptive in their behavior with respect to contention: when a thread attempts
to acquire a held adaptive lock, it will determine if the owning thread
is currently running on a CPU. If the owner is running on another
CPU, the acquiring thread will spin. If the owner is not running, the
acquiring thread will block.
The four lockstat probes pertaining to adaptive locks are in Table 18-1. For
each probe, arg0 contains a pointer to the kmutex_t structure that represents the
adaptive lock.
Table 18-1 Adaptive Lock Probes
adaptive-acquire |
Hold-event probe that fires immediately after an adaptive lock is acquired. |
adaptive-block |
Contention-event
probe that fires after a thread that has blocked on a held adaptive
mutex has reawakened and has acquired the mutex. If both probes are enabled,
adaptive-block fires before adaptive-acquire. A single lock acquisition can fire both the
adaptive-block and the adaptive-spin probes. arg1 for adaptive-block contains the sleep time in
nanoseconds. |
adaptive-spin |
Contention-event probe that fires after a thread that has spun on a held
adaptive mutex has successfully acquired the mutex. If both are enabled, adaptive-spin
fires before adaptive-acquire. A single lock acquisition can fire both the adaptive-block
and the adaptive-spin probes. arg1 for adaptive-spin contains the spin time: the number of nanoseconds
that were spent in the spin loop before the lock was acquired. |
adaptive-release |
Hold-event
probe that fires immediately after an adaptive lock is released. |
