linux-kernel - [PATCH net-next] hv_netvsc: Remove unnecessary round_up for recv_completion

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Date:   Mon, 30 Mar 2020 12:29:13 -0700
From:   Haiyang Zhang <haiyangz@...rosoft.com>
To:     sashal@...nel.org, linux-hyperv@...r.kernel.org,
        netdev@...r.kernel.org
Cc:     haiyangz@...rosoft.com, kys@...rosoft.com, sthemmin@...rosoft.com,
        olaf@...fle.de, vkuznets@...hat.com, davem@...emloft.net,
        linux-kernel@...r.kernel.org
Subject: [PATCH net-next] hv_netvsc: Remove unnecessary round_up for recv_completion_cnt

The vzalloc_node(), already rounds the total size to whole pages, and
sizeof(u64) is smaller than sizeof(struct recv_comp_data). So
round_up of recv_completion_cnt is not necessary, and may cause extra
memory allocation.

To save memory, remove this unnecessary round_up for recv_completion_cnt.

Signed-off-by: Haiyang Zhang <haiyangz@...rosoft.com>
---
 drivers/net/hyperv/netvsc.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 1b320bc..ca68aa1 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -388,10 +388,11 @@ static int netvsc_init_buf(struct hv_device *device,
 	net_device->recv_section_size = resp->sections[0].sub_alloc_size;
 	net_device->recv_section_cnt = resp->sections[0].num_sub_allocs;
 
-	/* Setup receive completion ring */
-	net_device->recv_completion_cnt
-		= round_up(net_device->recv_section_cnt + 1,
-			   PAGE_SIZE / sizeof(u64));
+	/* Setup receive completion ring.
+	 * Add 1 to the recv_section_cnt because at least one entry in a
+	 * ring buffer has to be empty.
+	 */
+	net_device->recv_completion_cnt = net_device->recv_section_cnt + 1;
 	ret = netvsc_alloc_recv_comp_ring(net_device, 0);
 	if (ret)
 		goto cleanup;
-- 
1.8.3.1