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=-6.9 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 autolearn=unavailable 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 DAA57C54FD0 for ; Mon, 27 Apr 2020 14:32:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AA83620656 for ; Mon, 27 Apr 2020 14:32:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="QDxH77TX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728094AbgD0Ocx (ORCPT ); Mon, 27 Apr 2020 10:32:53 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:31983 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727855AbgD0Ocx (ORCPT ); Mon, 27 Apr 2020 10:32:53 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587997971; 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=0u80QIqRuFtq393pEWCqHrz3SEQAL/TzXNi1FumiEQg=; b=QDxH77TX7AT28UumREjNz9/F9SXqqlZlRrB8SdiJfPckkB3MJ3mS/fLmBR56JGT2ne1d0G 7sIx8xJKVt7PtGRtAdmHMvvzXqbH4GP6F50NCFFfzn6zRhbImas36qUnletA9FtphjXj/5 /wWZ89/1gGLfQzcvvCa28BWv1wvLdb0= 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-508-uaarzkrsMMm9rifY-_Afew-1; Mon, 27 Apr 2020 10:32:41 -0400 X-MC-Unique: uaarzkrsMMm9rifY-_Afew-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 20E9C872FE0; Mon, 27 Apr 2020 14:32:38 +0000 (UTC) Received: from carbon (unknown [10.40.208.55]) by smtp.corp.redhat.com (Postfix) with ESMTP id 338DD1A924; Mon, 27 Apr 2020 14:32:25 +0000 (UTC) Date: Mon, 27 Apr 2020 16:32:24 +0200 From: Jesper Dangaard Brouer To: Jason Wang Cc: sameehj@amazon.com, netdev@vger.kernel.org, bpf@vger.kernel.org, zorik@amazon.com, akiyano@amazon.com, gtzalik@amazon.com, Toke =?UTF-8?B?SMO4aWxhbmQtSsO4cmdlbnNlbg==?= , 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, brouer@redhat.com Subject: Re: [PATCH net-next 21/33] virtio_net: add XDP frame size in two code paths Message-ID: <20200427163224.6445d4bb@carbon> In-Reply-To: <3958d9c6-a7d1-6a3d-941d-0a2915cc6b09@redhat.com> References: <158757160439.1370371.13213378122947426220.stgit@firesoul> <158757174774.1370371.14395462229209766397.stgit@firesoul> <3958d9c6-a7d1-6a3d-941d-0a2915cc6b09@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, 27 Apr 2020 15:21:02 +0800 Jason Wang wrote: > 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; =20 >=20 >=20 > Should this be PAGE_SIZE -=C2=A0 SKB_DATA_ALIGN(sizeof(struct skb_shared_= info))? No, frame_sz include the SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) len= gth. --=20 Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer