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

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Message-ID: <izmrcafyog7cxvef2nipk5f2vzxxptyc4fopnvl3heqslsp7q6@32ssw2piag6h>
Date: Fri, 27 Jun 2025 12:51:45 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Will Deacon <will@...nel.org>
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 Wed, Jun 25, 2025 at 02:15:38PM +0100, Will Deacon wrote:
>Hi folks,
>
>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!

Thanks,
Stefano

>
>Patches based on v6.16-rc3.
>
>Cheers,
>
>Will
>
>Cc: Keir Fraser <keirf@...gle.com>
>Cc: Steven Moreland <smoreland@...gle.com>
>Cc: Frederick Mayle <fmayle@...gle.com>
>Cc: Stefan Hajnoczi <stefanha@...hat.com>
>Cc: Stefano Garzarella <sgarzare@...hat.com>
>Cc: "Michael S. Tsirkin" <mst@...hat.com>
>Cc: Jason Wang <jasowang@...hat.com>
>Cc: "Eugenio Pérez" <eperezma@...hat.com>
>Cc: netdev@...r.kernel.org
>Cc: virtualization@...ts.linux.dev
>
>--->8
>
>Will Deacon (5):
>  vhost/vsock: Avoid allocating arbitrarily-sized SKBs
>  vsock/virtio: Resize receive buffers so that each SKB fits in a page
>  vhost/vsock: Allocate nonlinear SKBs for handling large receive
>    buffers
>  vsock/virtio: Rename virtio_vsock_skb_rx_put() to
>    virtio_vsock_skb_put()
>  vhost/vsock: Allocate nonlinear SKBs for handling large transmit
>    buffers
>
> drivers/vhost/vsock.c                   | 21 +++++++++------
> include/linux/virtio_vsock.h            | 36 +++++++++++++++++++------
> net/vmw_vsock/virtio_transport.c        |  2 +-
> net/vmw_vsock/virtio_transport_common.c |  9 +++++--
> 4 files changed, 49 insertions(+), 19 deletions(-)
>
>-- 
>2.50.0.714.g196bf9f422-goog
>
>