- Move rusage from being per-process in struct pstats to per-thread in

   td_ru.  This removes the requirement for per-process synchronization in
   statclock() and mi_switch().  This was previously supported by
   sched_lock which is going away.  All modifications to rusage are now
   done in the context of the owning thread.  reads proceed without locks.
 - Aggregate exiting threads rusage in thread_exit() such that the exiting
   thread's rusage is not lost.
 - Provide a new routine, rufetch() to fetch an aggregate of all rusage
   structures from all threads in a process.  This routine must be used
   in any place requiring a rusage from a process prior to it's exit.  The
   exited process's rusage is still available via p_ru.
 - Aggregate tick statistics only on demand via rufetch() or when a thread
   exits.  Tick statistics are kept in the thread and protected by sched_lock
   until it exits.

Initial patch by:	attilio
Reviewed by:		attilio, bde (some objections), arch (mostly silent)

1 files changed, 4 insertions, 6 deletions

diff --git a/sys/kern/kern_clock.c b/sys/kern/kern_clock.c
index ac404dc..0f7366a 100644
--- a/sys/kern/kern_clock.c
+++ b/sys/kern/kern_clock.c
@@ -394,10 +394,9 @@ stopprofclock(p)
 }
 
 /*
- * Statistics clock.  Grab profile sample, and if divider reaches 0,
- * do process and kernel statistics.  Most of the statistics are only
- * used by user-level statistics programs.  The main exceptions are
- * ke->ke_uticks, p->p_rux.rux_sticks, p->p_rux.rux_iticks, and p->p_estcpu.
+ * Statistics clock.  Updates rusage information and calls the scheduler
+ * to adjust priorities of the active thread.
+ *
  * This should be called by all active processors.
  */
 void
@@ -466,10 +465,9 @@ statclock(int usermode)
 	sched_clock(td);
 
 	/* Update resource usage integrals and maximums. */
-	MPASS(p->p_stats != NULL);
 	MPASS(p->p_vmspace != NULL);
 	vm = p->p_vmspace;
-	ru = &p->p_stats->p_ru;
+	ru = &td->td_ru;
 	ru->ru_ixrss += pgtok(vm->vm_tsize);
 	ru->ru_idrss += pgtok(vm->vm_dsize);
 	ru->ru_isrss += pgtok(vm->vm_ssize);