netdev - Re: [PATCH net v3 1/3] virtio-net: don't schedule delayed refill worker

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Message-ID: <20260110111053.08107da2@kernel.org>
Date: Sat, 10 Jan 2026 11:10:53 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Bui Quang Minh <minhquangbui99@...il.com>
Cc: netdev@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>, Jason
 Wang <jasowang@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Eugenio
 Pérez <eperezma@...hat.com>, Andrew Lunn
 <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Alexei
 Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend
 <john.fastabend@...il.com>, Stanislav Fomichev <sdf@...ichev.me>,
 virtualization@...ts.linux.dev, linux-kernel@...r.kernel.org,
 bpf@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH net v3 1/3] virtio-net: don't schedule delayed refill
 worker

On Sat, 10 Jan 2026 15:23:36 +0700 Bui Quang Minh wrote:
> >> @@ -3230,9 +3230,10 @@ static int virtnet_open(struct net_device *dev)
> >>   
> >>   	for (i = 0; i < vi->max_queue_pairs; i++) {
> >>   		if (i < vi->curr_queue_pairs)
> >> -			/* Make sure we have some buffers: if oom use wq. */
> >> -			if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL))
> >> -				schedule_delayed_work(&vi->refill, 0);
> >> +			/* Pre-fill rq agressively, to make sure we are ready to
> >> +			 * get packets immediately.
> >> +			 */
> >> +			try_fill_recv(vi, &vi->rq[i], GFP_KERNEL);  
> > We should enforce _some_ minimal fill level at the time of open().
> > If the ring is completely empty no traffic will ever flow, right?
> > Perhaps I missed scheduling the NAPI somewhere..  
> 
> The NAPI is enabled and scheduled in virtnet_napi_enable(). The code 
> path is like this
> 
> virtnet_enable_queue_pair
> -> virtnet_napi_enable  
>    -> virtnet_napi_do_enable
>      -> virtqueue_napi_schedule
> 
> The same happens in __virtnet_rx_resume().

I see. Alright, let me fix the nits while applying, no need to respin.
Kinda want this in the tree for a few days before shipping off to Linus.