git: 2a56cedac2e4 - main - bq_insert: delay the BUF_UNLOCK if not bd_flush()ing

The branch main has been updated by rlibby:

URL: https://cgit.FreeBSD.org/src/commit/?id=2a56cedac2e43c77e037e2d0c7e5af2ccb083c53

commit 2a56cedac2e43c77e037e2d0c7e5af2ccb083c53
Author:     Ryan Libby <rlibby@FreeBSD.org>
AuthorDate: 2026-05-13 17:43:21 +0000
Commit:     Ryan Libby <rlibby@FreeBSD.org>
CommitDate: 2026-05-13 17:43:21 +0000

    bq_insert: delay the BUF_UNLOCK if not bd_flush()ing
    
    Reduce bufqueue lock contention by delaying the BUF_UNLOCK to after
    dropping the bufqueue lock.  Still do the early BUF_UNLOCK if we
    actually have to bd_flush.
    
    Reviewed by:    kib, markj
    Sponsored by:   Dell Inc.
    Differential Revision:  https://reviews.freebsd.org/D56948
---
 sys/kern/vfs_bio.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index 675f6fb4e526..181f2907c245 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -2053,22 +2053,26 @@ bq_insert(struct bufqueue *bq, struct buf *bp, bool unlock)
 	bp->b_qindex = bq->bq_index;
 	bp->b_subqueue = bq->bq_subqueue;
 
-	/*
-	 * Unlock before we notify so that we don't wakeup a waiter that
-	 * fails a trylock on the buf and sleeps again.
-	 */
-	if (unlock)
-		BUF_UNLOCK(bp);
-
 	if (bp->b_qindex == QUEUE_CLEAN) {
 		/*
 		 * Flush the per-cpu queue and notify any waiters.
+		 *
+		 * Unlock before we notify so that we don't wakeup a waiter
+		 * that fails a trylock on the buf and sleeps again.
 		 */
 		if (bd->bd_wanted || (bq != bd->bd_cleanq &&
-		    bq->bq_len >= bd->bd_lim))
+		    bq->bq_len >= bd->bd_lim)) {
+			if (unlock) {
+				BUF_UNLOCK(bp);
+				unlock = false;
+			}
 			bd_flush(bd, bq);
+		}
 	}
 	BQ_UNLOCK(bq);
+
+	if (unlock)
+		BUF_UNLOCK(bp);
 }
 
 /*