git: a216e311a70c - main - vm_pageout_scan_inactive: take a lock break

The branch main has been updated by rlibby:

URL: https://cgit.FreeBSD.org/src/commit/?id=a216e311a70cc87a5646f4306e36c60a51706699

commit a216e311a70cc87a5646f4306e36c60a51706699
Author:     Ryan Libby <rlibby@FreeBSD.org>
AuthorDate: 2024-05-24 15:52:58 +0000
Commit:     Ryan Libby <rlibby@FreeBSD.org>
CommitDate: 2024-05-24 15:52:58 +0000

    vm_pageout_scan_inactive: take a lock break
    
    In vm_pageout_scan_inactive, release the object lock when we go to
    refill the scan batch queue so that someone else has a chance to acquire
    it.  This improves access latency to the object when the pagedaemon is
    processing many consecutive pages from a single object, and also in any
    case avoids a hiccup during refill for the last touched object.
    
    Reviewed by:    alc, markj (previous version)
    Sponsored by:   Dell EMC Isilon
    Differential Revision:  https://reviews.freebsd.org/D45288
---
 sys/vm/vm_pageout.c   | 16 +++++++++++++++-
 sys/vm/vm_pagequeue.h |  6 ++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/sys/vm/vm_pageout.c b/sys/vm/vm_pageout.c
index 8e9555c678c9..61f02eeb2f11 100644
--- a/sys/vm/vm_pageout.c
+++ b/sys/vm/vm_pageout.c
@@ -1451,7 +1451,21 @@ vm_pageout_scan_inactive(struct vm_domain *vmd, int page_shortage)
 	pq = &vmd->vmd_pagequeues[PQ_INACTIVE];
 	vm_pagequeue_lock(pq);
 	vm_pageout_init_scan(&ss, pq, marker, NULL, pq->pq_cnt);
-	while (page_shortage > 0 && (m = vm_pageout_next(&ss, true)) != NULL) {
+	while (page_shortage > 0) {
+		/*
+		 * If we need to refill the scan batch queue, release any
+		 * optimistically held object lock.  This gives someone else a
+		 * chance to grab the lock, and also avoids holding it while we
+		 * do unrelated work.
+		 */
+		if (object != NULL && vm_batchqueue_empty(&ss.bq)) {
+			VM_OBJECT_WUNLOCK(object);
+			object = NULL;
+		}
+
+		m = vm_pageout_next(&ss, true);
+		if (m == NULL)
+			break;
 		KASSERT((m->flags & PG_MARKER) == 0,
 		    ("marker page %p was dequeued", m));
 
diff --git a/sys/vm/vm_pagequeue.h b/sys/vm/vm_pagequeue.h
index 1fa80e718b71..7e133ec947b4 100644
--- a/sys/vm/vm_pagequeue.h
+++ b/sys/vm/vm_pagequeue.h
@@ -354,6 +354,12 @@ vm_batchqueue_init(struct vm_batchqueue *bq)
 	bq->bq_cnt = 0;
 }
 
+static inline bool
+vm_batchqueue_empty(const struct vm_batchqueue *bq)
+{
+	return (bq->bq_cnt == 0);
+}
+
 static inline int
 vm_batchqueue_insert(struct vm_batchqueue *bq, vm_page_t m)
 {