From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3275D78F4F; Mon, 18 Aug 2025 13:33:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755524020; cv=none; b=dDNCNchrxWF23CfhprZl1MK+qRPjU2li0RR5eG8c1UydiISDhmdSCaq3Evg5KAM5vFKQMXmkC/mK4tFvxllKrvgFTqZy9fOnqj6SZroPSNdMx9Uw5hv0gxFgYCZ3bTXgTnblbqDfjgWgggPoGYhp3/MMkX7DRgpzdkoJgLNuDDU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755524020; c=relaxed/simple; bh=RKHyd3OMgBLe3HIkXs2dJ2J6JCBGKaFPPk7lEgpYH5s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pybzmJx5be2irLK8ZR2xB5GxydgFuxAYTAu4vGRk2Cz2/tKFBG1WyPoDq9G3ARLg0HZ/GeWbiNQ5Rehcyr2RdmkjZQBRepH4N2CzbGWFS4WnQaxko6QkG8CL4eKHaOolU4yS833AOTnNA8umdHFuRWmQm/1d1Sw7xESCpHcrHqQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=obUw8WOD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="obUw8WOD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AE4B1C4CEEB; Mon, 18 Aug 2025 13:33:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1755524020; bh=RKHyd3OMgBLe3HIkXs2dJ2J6JCBGKaFPPk7lEgpYH5s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=obUw8WOD327dgHt/31boF1hcbjjdKZgFXQbG3FcZU1EqGbtHgQXycX/kblH3roVs7 hvxhB1SYwyMs+lOPZrz2r7L8ChOdMApYyqGn0fFo2YeQeo0otG9gr12Ee5SHvkAkLE bthAkQ0XJtPZZDqJ7bZ8WJYtZbNjUvUAD9oXigsE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Stefano Garzarella , Will Deacon , "Michael S. Tsirkin" , Sasha Levin Subject: [PATCH 6.15 326/515] vsock/virtio: Resize receive buffers so that each SKB fits in a 4K page Date: Mon, 18 Aug 2025 14:45:12 +0200 Message-ID: <20250818124510.985573855@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250818124458.334548733@linuxfoundation.org> References: <20250818124458.334548733@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Will Deacon [ Upstream commit 03a92f036a04fed2b00d69f5f46f1a486e70dc5c ] When allocating receive buffers for the vsock virtio RX virtqueue, an SKB is allocated with a 4140 data payload (the 44-byte packet header + VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE). Even when factoring in the SKB overhead, the resulting 8KiB allocation thanks to the rounding in kmalloc_reserve() is wasteful (~3700 unusable bytes) and results in a higher-order page allocation on systems with 4KiB pages just for the sake of a few hundred bytes of packet data. Limit the vsock virtio RX buffers to 4KiB per SKB, resulting in much better memory utilisation and removing the need to allocate higher-order pages entirely. Reviewed-by: Stefano Garzarella Signed-off-by: Will Deacon Message-Id: <20250717090116.11987-5-will@kernel.org> Signed-off-by: Michael S. Tsirkin Signed-off-by: Sasha Levin --- include/linux/virtio_vsock.h | 7 ++++++- net/vmw_vsock/virtio_transport.c | 2 +- 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h index 36fb3edfa403..6c00687539cf 100644 --- a/include/linux/virtio_vsock.h +++ b/include/linux/virtio_vsock.h @@ -111,7 +111,12 @@ static inline size_t virtio_vsock_skb_len(struct sk_buff *skb) return (size_t)(skb_end_pointer(skb) - skb->head); } -#define VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE (1024 * 4) +/* Dimension the RX SKB so that the entire thing fits exactly into + * a single 4KiB page. This avoids wasting memory due to alloc_skb() + * rounding up to the next page order and also means that we + * don't leave higher-order pages sitting around in the RX queue. + */ +#define VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE SKB_WITH_OVERHEAD(1024 * 4) #define VIRTIO_VSOCK_MAX_BUF_SIZE 0xFFFFFFFFUL #define VIRTIO_VSOCK_MAX_PKT_BUF_SIZE (1024 * 64) diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c index f0e48e6911fc..f01f9e878106 100644 --- a/net/vmw_vsock/virtio_transport.c +++ b/net/vmw_vsock/virtio_transport.c @@ -307,7 +307,7 @@ virtio_transport_cancel_pkt(struct vsock_sock *vsk) static void virtio_vsock_rx_fill(struct virtio_vsock *vsock) { - int total_len = VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE + VIRTIO_VSOCK_SKB_HEADROOM; + int total_len = VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE; struct scatterlist pkt, *p; struct virtqueue *vq; struct sk_buff *skb; -- 2.39.5