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Message-ID: <20240619041846-mutt-send-email-mst@kernel.org>
Date: Wed, 19 Jun 2024 04:23:25 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Jiri Pirko <jiri@...nulli.us>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
kuba@...nel.org, pabeni@...hat.com, jasowang@...hat.com,
xuanzhuo@...ux.alibaba.com, virtualization@...ts.linux.dev,
ast@...nel.org, daniel@...earbox.net, hawk@...nel.org,
john.fastabend@...il.com, dave.taht@...il.com,
kerneljasonxing@...il.com, hengqi@...ux.alibaba.com
Subject: Re: [PATCH net-next v3] virtio_net: add support for Byte Queue Limits
On Wed, Jun 19, 2024 at 10:05:41AM +0200, Jiri Pirko wrote:
> >Oh. Right of course. Worth a comment maybe? Just to make sure
> >we remember not to call __free_old_xmit twice in a row
> >without reinitializing stats.
> >Or move the initialization into __free_old_xmit to make it
> >self-contained ..
>
> Well, the initialization happens in the caller by {0}, Wouldn't
> memset in __free_old_xmit() add an extra overhead? IDK.
Well if I did the below the binary is a bit smaller.
If you have to respin you can include it.
If not I can submit separately.
----
virtio-net: cleanup __free_old_xmit
Two call sites of __free_old_xmit zero-initialize stats,
doing it inside __free_old_xmit seems to make compiler's
job a bit easier:
$ size /tmp/orig/virtio_net.o
text data bss dec hex filename
65857 3892 100 69849 110d9 /tmp/orig/virtio_net.o
$ size /tmp/new/virtio_net.o
text data bss dec hex filename
65760 3892 100 69752 11078 /tmp/new/virtio_net.o
Couldn't measure any performance impact, unsurprizingly.
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 283b34d50296..c2ce8de340f7 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -383,6 +383,8 @@ static void __free_old_xmit(struct send_queue *sq, bool in_napi,
unsigned int len;
void *ptr;
+ stats->bytes = stats->packets = 0;
+
while ((ptr = virtqueue_get_buf(sq->vq, &len)) != NULL) {
++stats->packets;
@@ -828,7 +830,7 @@ static void virtnet_rq_unmap_free_buf(struct virtqueue *vq, void *buf)
static void free_old_xmit(struct send_queue *sq, bool in_napi)
{
- struct virtnet_sq_free_stats stats = {0};
+ struct virtnet_sq_free_stats stats;
__free_old_xmit(sq, in_napi, &stats);
@@ -979,7 +981,7 @@ static int virtnet_xdp_xmit(struct net_device *dev,
int n, struct xdp_frame **frames, u32 flags)
{
struct virtnet_info *vi = netdev_priv(dev);
- struct virtnet_sq_free_stats stats = {0};
+ struct virtnet_sq_free_stats stats;
struct receive_queue *rq = vi->rq;
struct bpf_prog *xdp_prog;
struct send_queue *sq;
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