linux-kernel - [RFC v2 2/7] vhost_test: batch used buffer

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Message-Id: <20220817135718.2553-3-qtxuning1999@sjtu.edu.cn>
Date:   Wed, 17 Aug 2022 21:57:13 +0800
From:   Guo Zhi <qtxuning1999@...u.edu.cn>
To:     eperezma@...hat.com, jasowang@...hat.com, sgarzare@...hat.com,
        mst@...hat.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        Guo Zhi <qtxuning1999@...u.edu.cn>
Subject: [RFC v2 2/7] vhost_test: batch used buffer

Only add to used ring when a batch of buffer have all been used.  And if
in order feature negotiated, only add the last used descriptor for a
batch of buffer.

Signed-off-by: Guo Zhi <qtxuning1999@...u.edu.cn>
---
 drivers/vhost/test.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index bc8e7fb1e635..57cdb3a3edf6 100644
--- a/drivers/vhost/test.c
+++ b/drivers/vhost/test.c
@@ -43,6 +43,9 @@ struct vhost_test {
 static void handle_vq(struct vhost_test *n)
 {
 	struct vhost_virtqueue *vq = &n->vqs[VHOST_TEST_VQ];
+	struct vring_used_elem *heads = kmalloc(sizeof(*heads)
+			* vq->num, GFP_KERNEL);
+	int batch_idx = 0;
 	unsigned out, in;
 	int head;
 	size_t len, total_len = 0;
@@ -84,11 +87,14 @@ static void handle_vq(struct vhost_test *n)
 			vq_err(vq, "Unexpected 0 len for TX\n");
 			break;
 		}
-		vhost_add_used_and_signal(&n->dev, vq, head, 0);
+		heads[batch_idx].id = cpu_to_vhost32(vq, head);
+		heads[batch_idx++].len = cpu_to_vhost32(vq, len);
 		total_len += len;
 		if (unlikely(vhost_exceeds_weight(vq, 0, total_len)))
 			break;
 	}
+	if (batch_idx)
+		vhost_add_used_and_signal_n(&n->dev, vq, heads, batch_idx);
 
 	mutex_unlock(&vq->mutex);
 }
-- 
2.17.1