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 CD140283FD6; Tue, 1 Jul 2025 16:45:26 +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=1751388326; cv=none; b=kydTNDCBk1IAUwPLJduj4O2p/gNNPnh+ZU+a8GA7s+/ec9ZYgeePcDkumj4+2+fAWEtttDzR1KB4u0MRJwqU+DseJBQCh03hAhznelYohIRINpd8+WzBJanEKx7Bhvok1JnciJ/T5ew57rG9PFm1DUY22uGmcOhjlEJa26/tRD8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751388326; c=relaxed/simple; bh=B1w0qcrCgepHrxOTMugcVkliDb4+0LWgsIR7uZB8lLM=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=OS6RphYV4YchdchY+7PzqiX7xes09JrhfcrxgnFQQPRWKXO5UMZ9tRZkjr2DxVXznTgVCfip6qw/XwLTlwiDE+a1mszHfO4bJQLMjSHeNgKFlJVx38ELgLNAETlZnNjcP9KRvbqZuOu2NZ4ewMDxIjt8REBTixwfvTkInyuKbl4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oTn8bUBe; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="oTn8bUBe" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1E4F0C4CEEB; Tue, 1 Jul 2025 16:45:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1751388326; bh=B1w0qcrCgepHrxOTMugcVkliDb4+0LWgsIR7uZB8lLM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oTn8bUBeJ/lie7A6fbC05ty2k4Lfx7Ieir/ROFNOPROE5jTUOzeu3zrcWKosBxFpJ +0OLClWuoIuqv8+LmssHpix2mOYrOwEtI4bLUi/pCb/oBnwtjlQDlXICbOfnqCLwGU 8eb+7HpDOAwLm8zn4QcTHZiic+LCpi0fDnIK2VheEkyhNaH7HCO+3zYJTRUW32DntW atV/saUnkQyu5JAoe1aIqs7OU65J7aRJXu4FzL9xzeHsfyDGa1HtjuvPufpEi5dHGF 6nvQwy2pNIczC1s7JCcCKf29yOzprQ7DQFuEMYSYLDEVIMdYox6IX5JU+tJ2PGZU8x OTjBbQi+LJe6A== From: Will Deacon To: linux-kernel@vger.kernel.org Cc: Will Deacon , Keir Fraser , Steven Moreland , Frederick Mayle , Stefan Hajnoczi , Stefano Garzarella , "Michael S. Tsirkin" , Jason Wang , =?UTF-8?q?Eugenio=20P=C3=A9rez?= , netdev@vger.kernel.org, virtualization@lists.linux.dev Subject: [PATCH v2 4/8] vsock/virtio: Resize receive buffers so that each SKB fits in a page Date: Tue, 1 Jul 2025 17:45:03 +0100 Message-Id: <20250701164507.14883-5-will@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250701164507.14883-1-will@kernel.org> References: <20250701164507.14883-1-will@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 for the sake of a few hundred bytes of packet data. Limit the vsock virtio RX buffers to a page per SKB, resulting in much better memory utilisation and removing the need to allocate higher-order pages entirely. Signed-off-by: Will Deacon --- include/linux/virtio_vsock.h | 1 - net/vmw_vsock/virtio_transport.c | 7 ++++++- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h index eb6980aa19fd..1b5731186095 100644 --- a/include/linux/virtio_vsock.h +++ b/include/linux/virtio_vsock.h @@ -109,7 +109,6 @@ 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) #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 488e6ddc6ffa..3daba06ed499 100644 --- a/net/vmw_vsock/virtio_transport.c +++ b/net/vmw_vsock/virtio_transport.c @@ -307,7 +307,12 @@ 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; + /* Dimension the SKB so that the entire thing fits exactly into + * a single 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. + */ + int total_len = SKB_WITH_OVERHEAD(PAGE_SIZE); struct scatterlist pkt, *p; struct virtqueue *vq; struct sk_buff *skb; -- 2.50.0.727.gbf7dc18ff4-goog