From 2a56cedac2e43c77e037e2d0c7e5af2ccb083c53 Mon Sep 17 00:00:00 2001 From: Ryan Libby Date: Wed, 13 May 2026 10:43:21 -0700 Subject: [PATCH] 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 675f6fb4e52..181f2907c24 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); } /*