rangelocks: stop caching per-thread rl_q_entry

This should reduce the frequency of smr_synchronize() calls, that
otherwise occur on almost each rangelock unlock.

Reviewed by:	markj
Sponsored by:	The FreeBSD Foundation
Differential revision:	https://reviews.freebsd.org/D46482

4 files changed, 4 insertions, 27 deletions

diff --git a/sys/kern/kern_rangelock.c b/sys/kern/kern_rangelock.c
index 3a11059a7f64..3437e3da77ba 100644
--- a/sys/kern/kern_rangelock.c
+++ b/sys/kern/kern_rangelock.c
@@ -313,15 +313,8 @@ static struct rl_q_entry *
 rlqentry_alloc(vm_ooffset_t start, vm_ooffset_t end, int flags)
 {
 	struct rl_q_entry *e;
-	struct thread *td;
-
-	td = curthread;
-	if (td->td_rlqe != NULL) {
-		e = td->td_rlqe;
-		td->td_rlqe = NULL;
-	} else {
-		e = uma_zalloc_smr(rl_entry_zone, M_WAITOK);
-	}
+
+	e = uma_zalloc_smr(rl_entry_zone, M_WAITOK);
 	e->rl_q_next = NULL;
 	e->rl_q_free = NULL;
 	e->rl_q_start = start;
@@ -334,12 +327,6 @@ rlqentry_alloc(vm_ooffset_t start, vm_ooffset_t end, int flags)
 }
 
 void
-rangelock_entry_free(struct rl_q_entry *e)
-{
-	uma_zfree_smr(rl_entry_zone, e);
-}
-
-void
 rangelock_init(struct rangelock *lock)
 {
 	lock->sleepers = false;
@@ -401,19 +388,12 @@ static void
 rangelock_free_free(struct rl_q_entry *free)
 {
 	struct rl_q_entry *x, *xp;
-	struct thread *td;
 
-	td = curthread;
 	for (x = free; x != NULL; x = xp) {
 		MPASS(!rl_e_is_marked(x));
 		xp = x->rl_q_free;
 		MPASS(!rl_e_is_marked(xp));
-		if (td->td_rlqe == NULL) {
-			smr_synchronize(rl_smr);
-			td->td_rlqe = x;
-		} else {
-			uma_zfree_smr(rl_entry_zone, x);
-		}
+		uma_zfree_smr(rl_entry_zone, x);
 	}
 }
 
diff --git a/sys/kern/kern_thread.c b/sys/kern/kern_thread.c
index 9c3694feb945..4ccd6b26528e 100644
--- a/sys/kern/kern_thread.c
+++ b/sys/kern/kern_thread.c
@@ -460,7 +460,6 @@ thread_init(void *mem, int size, int flags)
 	td->td_allocdomain = vm_phys_domain(vtophys(td));
 	td->td_sleepqueue = sleepq_alloc();
 	td->td_turnstile = turnstile_alloc();
-	td->td_rlqe = NULL;
 	EVENTHANDLER_DIRECT_INVOKE(thread_init, td);
 	umtx_thread_init(td);
 	td->td_kstack = 0;
@@ -480,7 +479,6 @@ thread_fini(void *mem, int size)
 	EVENTHANDLER_DIRECT_INVOKE(thread_fini, td);
 	turnstile_free(td->td_turnstile);
 	sleepq_free(td->td_sleepqueue);
-	rangelock_entry_free(td->td_rlqe);
 	umtx_thread_fini(td);
 	MPASS(td->td_sel == NULL);
 }
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index 57c910d8fce0..1e98cc84a60a 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -247,7 +247,7 @@ struct thread {
 	struct seltd	*td_sel;	/* Select queue/channel. */
 	struct sleepqueue *td_sleepqueue; /* (k) Associated sleep queue. */
 	struct turnstile *td_turnstile;	/* (k) Associated turnstile. */
-	struct rl_q_entry *td_rlqe;	/* (k) Associated range lock entry. */
+	void		*td_pad1;	/* Available */
 	struct umtx_q   *td_umtxq;	/* (c?) Link for when we're blocked. */
 	lwpid_t		td_tid;		/* (b) Thread ID. */
 	sigqueue_t	td_sigqueue;	/* (c) Sigs arrived, not delivered. */
diff --git a/sys/sys/rangelock.h b/sys/sys/rangelock.h
index accf33d7296b..32ccf3427b49 100644
--- a/sys/sys/rangelock.h
+++ b/sys/sys/rangelock.h
@@ -65,7 +65,6 @@ void	*rangelock_wlock(struct rangelock *lock, vm_ooffset_t start,
     vm_ooffset_t end);
 void	*rangelock_trywlock(struct rangelock *lock, vm_ooffset_t start,
     vm_ooffset_t end);
-void	 rangelock_entry_free(struct rl_q_entry *e);
 void	rangelock_may_recurse(struct rangelock *lock);
 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
 void	_rangelock_cookie_assert(void *cookie, int what, const char *file,