From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2C63C55199 for ; Mon, 27 Apr 2020 07:21:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B128B2072D for ; Mon, 27 Apr 2020 07:21:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="QDe4n2l4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726625AbgD0HVY (ORCPT ); Mon, 27 Apr 2020 03:21:24 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:31394 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726349AbgD0HVY (ORCPT ); Mon, 27 Apr 2020 03:21:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587972083; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=gmrqhUr63ylUIBJ0HetA0W/F7e91Q2QoSF5xiRnj80k=; b=QDe4n2l4jFP5WfoLGMdrK6kRBoz1GvAIz/rk576H6kYtLcUWtT5l6kw49vQHT8/ZHDM1mi VXSy9tews6Pnc6tSDlbI1tjgXxqrso8pb6Nwf/GyD/5qCSqzw2zYoO9FgXC1LyuXZLUDzq OwNEClsIc+ZdRgG/y11GIQ01A7sJjAs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-55-MYQl7MChPPyI20unIZ4TkQ-1; Mon, 27 Apr 2020 03:21:18 -0400 X-MC-Unique: MYQl7MChPPyI20unIZ4TkQ-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2532C107ACF9; Mon, 27 Apr 2020 07:21:16 +0000 (UTC) Received: from [10.72.12.205] (ovpn-12-205.pek2.redhat.com [10.72.12.205]) by smtp.corp.redhat.com (Postfix) with ESMTP id 82AF760CD3; Mon, 27 Apr 2020 07:21:04 +0000 (UTC) Subject: Re: [PATCH net-next 21/33] virtio_net: add XDP frame size in two code paths To: Jesper Dangaard Brouer , sameehj@amazon.com Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, zorik@amazon.com, akiyano@amazon.com, gtzalik@amazon.com, =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= , Daniel Borkmann , Alexei Starovoitov , John Fastabend , Alexander Duyck , Jeff Kirsher , David Ahern , Willem de Bruijn , Ilias Apalodimas , Lorenzo Bianconi , Saeed Mahameed , steffen.klassert@secunet.com References: <158757160439.1370371.13213378122947426220.stgit@firesoul> <158757174774.1370371.14395462229209766397.stgit@firesoul> From: Jason Wang Message-ID: <3958d9c6-a7d1-6a3d-941d-0a2915cc6b09@redhat.com> Date: Mon, 27 Apr 2020 15:21:02 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <158757174774.1370371.14395462229209766397.stgit@firesoul> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Content-Transfer-Encoding: quoted-printable Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2020/4/23 =E4=B8=8A=E5=8D=8812:09, Jesper Dangaard Brouer wrote: > The virtio_net driver is running inside the guest-OS. There are two > XDP receive code-paths in virtio_net, namely receive_small() and > receive_mergeable(). The receive_big() function does not support XDP. > > In receive_small() the frame size is available in buflen. The buffer > backing these frames are allocated in add_recvbuf_small() with same > size, except for the headroom, but tailroom have reserved room for > skb_shared_info. The headroom is encoded in ctx pointer as a value. > > In receive_mergeable() the frame size is more dynamic. There are two > basic cases: (1) buffer size is based on a exponentially weighted > moving average (see DECLARE_EWMA) of packet length. Or (2) in case > virtnet_get_headroom() have any headroom then buffer size is > PAGE_SIZE. The ctx pointer is this time used for encoding two values; > the buffer len "truesize" and headroom. In case (1) if the rx buffer > size is underestimated, the packet will have been split over more > buffers (num_buf info in virtio_net_hdr_mrg_rxbuf placed in top of > buffer area). If that happens the XDP path does a xdp_linearize_page > operation. > > Cc: Jason Wang > Signed-off-by: Jesper Dangaard Brouer > --- > drivers/net/virtio_net.c | 15 ++++++++++++--- > 1 file changed, 12 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 11f722460513..1df3676da185 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -689,6 +689,7 @@ static struct sk_buff *receive_small(struct net_dev= ice *dev, > xdp.data_end =3D xdp.data + len; > xdp.data_meta =3D xdp.data; > xdp.rxq =3D &rq->xdp_rxq; > + xdp.frame_sz =3D buflen; > orig_data =3D xdp.data; > act =3D bpf_prog_run_xdp(xdp_prog, &xdp); > stats->xdp_packets++; > @@ -797,10 +798,11 @@ static struct sk_buff *receive_mergeable(struct n= et_device *dev, > int offset =3D buf - page_address(page); > struct sk_buff *head_skb, *curr_skb; > struct bpf_prog *xdp_prog; > - unsigned int truesize; > + unsigned int truesize =3D mergeable_ctx_to_truesize(ctx); > unsigned int headroom =3D mergeable_ctx_to_headroom(ctx); > - int err; > unsigned int metasize =3D 0; > + unsigned int frame_sz; > + int err; > =20 > head_skb =3D NULL; > stats->bytes +=3D len - vi->hdr_len; > @@ -821,6 +823,11 @@ static struct sk_buff *receive_mergeable(struct ne= t_device *dev, > if (unlikely(hdr->hdr.gso_type)) > goto err_xdp; > =20 > + /* Buffers with headroom use PAGE_SIZE as alloc size, > + * see add_recvbuf_mergeable() + get_mergeable_buf_len() > + */ > + frame_sz =3D headroom ? PAGE_SIZE : truesize; > + > /* This happens when rx buffer size is underestimated > * or headroom is not enough because of the buffer > * was refilled before XDP is set. This should only > @@ -834,6 +841,8 @@ static struct sk_buff *receive_mergeable(struct net= _device *dev, > page, offset, > VIRTIO_XDP_HEADROOM, > &len); > + frame_sz =3D PAGE_SIZE; Should this be PAGE_SIZE -=C2=A0 SKB_DATA_ALIGN(sizeof(struct skb_shared_= info))? > + > if (!xdp_page) > goto err_xdp; > offset =3D VIRTIO_XDP_HEADROOM; > @@ -850,6 +859,7 @@ static struct sk_buff *receive_mergeable(struct net= _device *dev, > xdp.data_end =3D xdp.data + (len - vi->hdr_len); > xdp.data_meta =3D xdp.data; > xdp.rxq =3D &rq->xdp_rxq; > + xdp.frame_sz =3D frame_sz; Maybe we can easily check by xdp.frame_sz =3D (xdp_page =3D=3D page) ? truesize : ... Thanks > =20 > act =3D bpf_prog_run_xdp(xdp_prog, &xdp); > stats->xdp_packets++; > @@ -924,7 +934,6 @@ static struct sk_buff *receive_mergeable(struct net= _device *dev, > } > rcu_read_unlock(); > =20 > - truesize =3D mergeable_ctx_to_truesize(ctx); > if (unlikely(len > truesize)) { > pr_debug("%s: rx error: len %u exceeds truesize %lu\n", > dev->name, len, (unsigned long)ctx); > >