From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f65.google.com ([209.85.208.65]:42160 "EHLO mail-ed1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728309AbfEWLLY (ORCPT ); Thu, 23 May 2019 07:11:24 -0400 Received: by mail-ed1-f65.google.com with SMTP id l25so8640040eda.9 for ; Thu, 23 May 2019 04:11:23 -0700 (PDT) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= Subject: Re: [PATCH bpf-next 1/3] xdp: Add bulk XDP_TX queue In-Reply-To: <1558609008-2590-2-git-send-email-makita.toshiaki@lab.ntt.co.jp> References: <1558609008-2590-1-git-send-email-makita.toshiaki@lab.ntt.co.jp> <1558609008-2590-2-git-send-email-makita.toshiaki@lab.ntt.co.jp> Date: Thu, 23 May 2019 13:11:20 +0200 Message-ID: <8736l52zon.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain Sender: xdp-newbies-owner@vger.kernel.org List-ID: To: Toshiaki Makita , Alexei Starovoitov , Daniel Borkmann , "David S. Miller" , Jakub Kicinski , Jesper Dangaard Brouer , John Fastabend Cc: netdev@vger.kernel.org, xdp-newbies@vger.kernel.org, bpf@vger.kernel.org Toshiaki Makita writes: > XDP_TX is similar to XDP_REDIRECT as it essentially redirects packets to > the device itself. XDP_REDIRECT has bulk transmit mechanism to avoid the > heavy cost of indirect call but it also reduces lock acquisition on the > destination device that needs locks like veth and tun. > > XDP_TX does not use indirect calls but drivers which require locks can > benefit from the bulk transmit for XDP_TX as well. XDP_TX happens on the same device, so there's an implicit bulking happening because of the NAPI cycle. So why is an additional mechanism needed (in the general case)? -Toke