11.8.1 sched Probes

The following table describes the probes for the sched provider.

Table 11.7 sched Probes

Probe

Description

change-pri

Fires whenever a thread's priority is about to be changed. The lwpsinfo_t of the thread is pointed to by args[0]. The thread's current priority is in the pr_pri field of this structure. The psinfo_t of the process containing the thread is pointed to by args[1]. The thread's new priority is contained in args[2].

dequeue

Fires immediately before a runnable thread is dequeued from a run queue. The lwpsinfo_t of the thread being dequeued is pointed to by args[0]. The psinfo_t of the process containing the thread is pointed to by args[1]. The cpuinfo_t of the CPU from which the thread is being dequeued is pointed to by args[2]. If the thread is being dequeued from a run queue that is not associated with a particular CPU, the cpu_id member of this structure will be -1.

enqueue

Fires immediately before a runnable thread is enqueued to a run queue. The lwpsinfo_t of the thread being enqueued is pointed to by args[0]. The psinfo_t of the process containing the thread is pointed to by args[1]. The cpuinfo_t of the CPU to which the thread is being enqueued is pointed to by args[2]. If the thread is being enqueued from a run queue that is not associated with a particular CPU, the cpu_id member of this structure will be -1. The value in args[3] is a boolean indicating whether the thread will be enqueued to the front of the run queue. The value is non-zero if the thread will be enqueued at the front of the run queue, and zero if the thread will be enqueued at the back of the run queue.

off-cpu

Fires when the current CPU is about to end execution of a thread. The curcpu variable indicates the current CPU. The curlwpsinfo variable indicates the thread that is ending execution. The lwpsinfo_t of the thread that the current CPU will next execute is pointed to by args[0]. The psinfo_t of the process containing the next thread is pointed to by args[1].

on-cpu

Fires when a CPU has just begun execution of a thread. The curcpu variable indicates the current CPU. The curlwpsinfo variable indicates the thread that is beginning execution. The curpsinfo variable describes the process containing the current thread.

preempt

Fires immediately before the current thread is preempted. After this probe fires, the current thread will select a thread to run and the off-cpu probe will fire for the current thread. In some cases, a thread on one CPU will be preempted, but the preempting thread will run on another CPU in the meantime. In this situation, the preempt probe will fire, but the dispatcher will be unable to find a higher priority thread to run and the remain-cpu probe will fire instead of the off-cpu probe.

remain-cpu

Fires when a scheduling decision has been made, but the dispatcher has elected to continue to run the current thread. The curcpu variable indicates the current CPU. The curlwpsinfo variable indicates the thread that is beginning execution. The curpsinfo variable describes the process containing the current thread.

sleep

Fires immediately before the current thread sleeps on a synchronization object. The type of the synchronization object is contained in the pr_stype member of the lwpsinfo_t pointed to by curlwpsinfo. The address of the synchronization object is contained in the pr_wchan member of the lwpsinfo_t pointed to by curlwpsinfo. The meaning of this address is a private implementation detail, but the address value may be treated as a token unique to the synchronization object.

surrender

Fires when a CPU has been instructed by another CPU to make a scheduling decision — often because a higher-priority thread has become runnable. The lwpsinfo_t of the current thread is pointed to by args[0]. The psinfo_t of the process containing the thread is pointed to by args[1].

tick

Fires as a part of clock tick-based accounting. In clock tick-based accounting, CPU accounting is performed by examining which threads and processes are running when a fixed-interval interrupt fires. The lwpsinfo_t that corresponds to the thread that is being assigned CPU time is pointed to by args[0]. The psinfo_t that corresponds to the process that contains the thread is pointed to by args[1].

wakeup

Fires immediately before the current thread wakes a thread sleeping on a synchronization object. The lwpsinfo_t of the sleeping thread is pointed to by args[0]. The psinfo_t of the process containing the sleeping thread is pointed to by args[1]. The type of the synchronization object is contained in the pr_stype member of the lwpsinfo_t of the sleeping thread. The address of the synchronization object is contained in the pr_wchan member of the lwpsinfo_t of the sleeping thread. The meaning of this address is a private implementation detail, but the address value may be treated as a token unique to the synchronization object.