linux-kernel - Re: [PATCH 0/5] vsock/virtio: SKB allocation improvements

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Message-ID: <aGKII2RcxMpBY3Zc@willie-the-truck>
Date: Mon, 30 Jun 2025 13:50:43 +0100
From: Will Deacon <will@...nel.org>
To: Stefano Garzarella <sgarzare@...hat.com>
Cc: linux-kernel@...r.kernel.org, Keir Fraser <keirf@...gle.com>,
	Steven Moreland <smoreland@...gle.com>,
	Frederick Mayle <fmayle@...gle.com>,
	Stefan Hajnoczi <stefanha@...hat.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Jason Wang <jasowang@...hat.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	netdev@...r.kernel.org, virtualization@...ts.linux.dev
Subject: Re: [PATCH 0/5] vsock/virtio: SKB allocation improvements

On Fri, Jun 27, 2025 at 12:51:45PM +0200, Stefano Garzarella wrote:
> On Wed, Jun 25, 2025 at 02:15:38PM +0100, Will Deacon wrote:
> > We're using vsock extensively in Android as a channel over which we can
> > route binder transactions to/from virtual machines managed by the
> > Android Virtualisation Framework. However, we have been observing some
> > issues in production builds when using vsock in a low-memory environment
> > (on the host and the guest) such as:
> > 
> >  * The host receive path hanging forever, despite the guest performing
> >    a successful write to the socket.
> > 
> >  * Page allocation failures in the vhost receive path (this is a likely
> >    contributor to the above)
> > 
> >  * -ENOMEM coming back from sendmsg()
> > 
> > This series aims to improve the vsock SKB allocation for both the host
> > (vhost) and the guest when using the virtio transport to help mitigate
> > these issues. Specifically:
> > 
> >  - Avoid single allocations of order > PAGE_ALLOC_COSTLY_ORDER
> > 
> >  - Use non-linear SKBs for the transmit and vhost receive paths
> > 
> >  - Reduce the guest RX buffers to a single page
> > 
> > There are more details in the individual commit messages but overall
> > this results in less wasted memory and puts less pressure on the
> > allocator.
> > 
> > This is my first time looking at this stuff, so all feedback is welcome.
> 
> Thank you very much for this series!
> 
> I left some minor comments, but overall LGTM!

Cheers for going through it! I'll work through your comments now...

Will