Some small fixes to CPU accounting for threads:

- Only initialize the per-cpu switchticks and switchtime in sched_throw()
  for the very first context switch on APs during boot.  This avoids a
  small gap between the middle of thread_exit() and sched_throw() where
  time is not accounted to any thread.
- In thread_exit(), update the timestamp bookkeeping to track the changes
  to mi_switch() introduced by td_rux so that the code once again matches
  the comment claiming it is mimicing mi_switch().  Specifically, only
  update the per-thread stats directly and depend on ruxagg() to update
  p_rux rather than adjusting p_rux directly.  While here, move the
  timestamp bookkeeping as late in the function as possible.

Reviewed by:	bde, kib
MFC after:	1 week

1 files changed, 2 insertions, 2 deletions

diff --git a/sys/kern/sched_ule.c b/sys/kern/sched_ule.c
index 87e3655..2065b9f 100644
--- a/sys/kern/sched_ule.c
+++ b/sys/kern/sched_ule.c
@@ -2587,6 +2587,8 @@ sched_throw(struct thread *td)
 		/* Correct spinlock nesting and acquire the correct lock. */
 		TDQ_LOCK(tdq);
 		spinlock_exit();
+		PCPU_SET(switchtime, cpu_ticks());
+		PCPU_SET(switchticks, ticks);
 	} else {
 		MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
 		tdq_load_rem(tdq, td);
@@ -2595,8 +2597,6 @@ sched_throw(struct thread *td)
 	KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
 	newtd = choosethread();
 	TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
-	PCPU_SET(switchtime, cpu_ticks());
-	PCPU_SET(switchticks, ticks);
 	cpu_throw(td, newtd);		/* doesn't return */
 }