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Fri, 24 Apr 2020 07:04:45 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([45.145.92.2]) by smtp.gmail.com with ESMTPSA id z13sm4316533ljn.77.2020.04.24.07.04.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Apr 2020 07:04:32 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 889121814FF; Fri, 24 Apr 2020 16:04:19 +0200 (CEST) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Jesper Dangaard Brouer , sameehj@amazon.com Cc: Jesper Dangaard Brouer , netdev@vger.kernel.org, bpf@vger.kernel.org, zorik@amazon.com, akiyano@amazon.com, gtzalik@amazon.com, 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 Subject: Re: [PATCH net-next 08/33] xdp: cpumap redirect use frame_sz and increase skb_tailroom In-Reply-To: <158757168168.1370371.11510167625755235041.stgit@firesoul> References: <158757160439.1370371.13213378122947426220.stgit@firesoul> <158757168168.1370371.11510167625755235041.stgit@firesoul> X-Clacks-Overhead: GNU Terry Pratchett Date: Fri, 24 Apr 2020 16:04:19 +0200 Message-ID: <875zdp3rq4.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Jesper Dangaard Brouer writes: > Knowing the memory size backing the packet/xdp_frame data area, and > knowing it already have reserved room for skb_shared_info, simplifies > using build_skb significantly. > > With this change we no-longer lie about the SKB truesize, but more > importantly a significant larger skb_tailroom is now provided, e.g. when > drivers uses a full PAGE_SIZE. This extra tailroom (in linear area) can be > used by the network stack when coalescing SKBs (e.g. in skb_try_coalesce, > see TCP cases where tcp_queue_rcv() can 'eat' skb). > > Signed-off-by: Jesper Dangaard Brouer Acked-by: Toke H=C3=B8iland-J=C3=B8rgensen