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From: Xianting Tian <xianting.tian@linux.alibaba.com>
To: mst@redhat.com, jasowang@redhat.com, sgarzare@redhat.com
Cc: virtualization@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org,
	Xianting Tian <xianting.tian@linux.alibaba.com>
Subject: [PATCH 2/2] virtio_ring: add unlikely annotation for free descs check
Date: Mon, 28 Mar 2022 18:58:17 +0800	[thread overview]
Message-ID: <20220328105817.1028065-2-xianting.tian@linux.alibaba.com> (raw)
In-Reply-To: <20220328105817.1028065-1-xianting.tian@linux.alibaba.com>

The 'if (vq->vq.num_free < descs_used)' check will almost always be false.

Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com>
---
 drivers/virtio/virtio_ring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index d597fc0874ec..ab6d5f0cb579 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -525,7 +525,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
 		descs_used = total_sg;
 	}
 
-	if (vq->vq.num_free < descs_used) {
+	if (unlikely(vq->vq.num_free < descs_used)) {
 		pr_debug("Can't add buf len %i - avail = %i\n",
 			 descs_used, vq->vq.num_free);
 		/* FIXME: for historical reasons, we force a notify here if
-- 
2.17.1


  reply	other threads:[~2022-03-28 10:58 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-28 10:58 [PATCH 1/2] virtio_ring: remove unnecessary to_vvq call in vring hot path Xianting Tian
2022-03-28 10:58 ` Xianting Tian [this message]
2022-03-29  4:57   ` [PATCH 2/2] virtio_ring: add unlikely annotation for free descs check Jason Wang
2022-03-29  4:57     ` Jason Wang
2022-03-29  7:50   ` Stefano Garzarella
2022-03-29  7:50     ` Stefano Garzarella
2022-04-04 15:11     ` Xianting Tian
2022-04-04 16:27       ` Michael S. Tsirkin
2022-04-04 16:27         ` Michael S. Tsirkin
2022-03-29  4:56 ` [PATCH 1/2] virtio_ring: remove unnecessary to_vvq call in vring hot path Jason Wang
2022-03-29  4:56   ` Jason Wang
2022-03-29  7:49 ` Stefano Garzarella
2022-03-29  7:49   ` Stefano Garzarella

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