kernel: Remove unused hogticks global from kern_synch.c.

hogticks was a global definition used in kern_synch.c:should_yield().
A thread that had remained running for more than hogticks would
return true for should_yield(). DragonFly has not used this global
for a long time.

Submitted-by:  vsrinivas
Dragonfly-bug: <https://bugs.dragonflybsd.org/issues/2787>

sys/kern/kern_synch.c

@@ -67,7 +67,6 @@ TAILQ_HEAD(tslpque, thread);
 static void sched_setup (void *dummy);
 SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL)
 
-int	hogticks;
 int	lbolt;
 void	*lbolt_syncer;
 int	sched_quantum;		/* Roundrobin scheduling quantum in ticks. */
@@ -129,7 +128,6 @@ sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
 	if (new_val < ustick)
 		return (EINVAL);
 	sched_quantum = new_val / ustick;
-	hogticks = 2 * sched_quantum;
 	return (0);
 }
 
@@ -327,8 +325,6 @@ sleep_gdinit(globaldata_t gd)
 
 	if (gd->gd_cpuid == 0) {
 		sched_quantum = (hz + 24) / 25;
-		hogticks = 2 * sched_quantum;
-
 		gd->gd_tsleep_hash = slpque_cpu0;
 	} else {
 		gd->gd_tsleep_hash = kmalloc(sizeof(slpque_cpu0), 

sys/sys/proc.h

@@ -498,7 +498,6 @@ extern void stopevent(struct proc*, unsigned int, unsigned int);
 extern struct proc proc0;		/* Process slot for swapper. */
 extern struct lwp lwp0;			/* LWP slot for swapper. */
 extern struct thread thread0;		/* Thread slot for swapper. */
-extern int hogticks;			/* Limit on kernel cpu hogs. */
 extern int nprocs, maxproc;		/* Current and max number of procs. */
 extern int maxprocperuid;		/* Max procs per uid. */
 extern int sched_quantum;		/* Scheduling quantum in ticks */