netdev - Re: [PATCH net 1/3] virtio-net: make refill work a per receive queue work

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Message-ID: <20251223204555-mutt-send-email-mst@kernel.org>
Date: Tue, 23 Dec 2025 20:47:50 -0500
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: Jason Wang <jasowang@...hat.com>, netdev@...r.kernel.org,
	Eugenio Pérez <eperezma@...hat.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, 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, Bui Quang Minh <minhquangbui99@...il.com>
Subject: Re: [PATCH net 1/3] virtio-net: make refill work a per receive queue
 work

On Wed, Dec 24, 2025 at 09:37:14AM +0800, Xuan Zhuo wrote:
> 
> Hi Jason,
> 
> I'm wondering why we even need this refill work. Why not simply let NAPI retry
> the refill on its next run if the refill fails? That would seem much simpler.
> This refill work complicates maintenance and often introduces a lot of
> concurrency issues and races.
> 
> Thanks.

refill work can refill from GFP_KERNEL, napi only from ATOMIC.

And if GFP_ATOMIC failed, aggressively retrying might not be a great idea.

Not saying refill work is a great hack, but that is the reason for it.
-- 
MST