From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-io1-xd36.google.com (mail-io1-xd36.google.com [IPv6:2607:f8b0:4864:20::d36]) by mail.toke.dk (Postfix) with ESMTPS id 1107A8EB0A4 for ; Mon, 22 Nov 2021 13:45:50 +0100 (CET) Authentication-Results: mail.toke.dk; dkim=pass (2048-bit key) header.d=mojatatu-com.20210112.gappssmtp.com header.i=@mojatatu-com.20210112.gappssmtp.com header.b=Y2ai5KOt Received: by mail-io1-xd36.google.com with SMTP id z26so23081440iod.10 for ; Mon, 22 Nov 2021 04:45:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mojatatu-com.20210112.gappssmtp.com; s=20210112; h=message-id:date:mime-version:user-agent:subject:content-language:to :cc:references:from:in-reply-to:content-transfer-encoding; bh=EqEpMzScOqdsapd5jOX8kKfXB3QN0tZkvX6LGlEvyAA=; b=Y2ai5KOt+BP5E7HFFZLAEn/nqKGcig92/h+J3zfdvho8a3JRaumMz5EnI+r6Cou3Co PPg4IwY0vSyVG5NfShAmpY+VDyQAAb5iecE0AlJCJfW7MysvPNiUfwoJlX2kn4PEpMDi THiS31Fz77c5NL4wRscxNVRwZLzoJ/mteyyJ0CjQjKl7Axiv/OXd31HZr37Ud0jrRAJf Dji1EXfpidxIbF6tQTDur65THHfxGsuwsQy5Gb9ddu4KKuqZNV12KO/dK1+/wc/nFp1p 9A8RNaQjQsEtQe6qQId1rXd6EzTMH4VqH2Ibg1lJwte4esxJqstvLfQQ0z+oYW4cwb0l WvZA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=EqEpMzScOqdsapd5jOX8kKfXB3QN0tZkvX6LGlEvyAA=; b=upnUB2+vXYsMEcdod5zaq6+/noRVUokNbRG8cd8XseTOPPZog2hVQOYW34epWbdWmK rfmbaE4JXy21rTgeDFl/OFaruFs8limdPjh+V11zVLvvEr+U+2Qf0U2WETvfYvs4Xyg6 ip9Odpv8o5WLLBJbwESlWiD0C52XGBDKcuFDYQSVgSbFZCF8KIE/pqvNnVIHHAyOwPrZ KhaB9dy6P/63qZ9XprHhDnRbbgKry2DHWp6dJmXMErKRRKf2R7dhJ/uZDu25Ae/NnNxY u9QfPHtRMzY6cfbRQAMGrkjz/Vw6Liw0p/iINXn4EmC0BqRJrTNHHUbCAtYhdjmJ+Aq1 VnLw== X-Gm-Message-State: AOAM532c5ISr//0SIDA0b/qsG6jou50Lin9lhBWZXDaWxcVTQYD2CAov 3VeShxobBju5Y0fxRjgkPV2NWw== X-Google-Smtp-Source: ABdhPJwFRHdbzL1pOkCx/G7Gpt8qOOHTyrGQgAFvR2mLA6pdvQlYbdCIMKqraiBw0O83qJPhh+Mf9A== X-Received: by 2002:a05:6602:280f:: with SMTP id d15mr22120355ioe.150.1637585148996; Mon, 22 Nov 2021 04:45:48 -0800 (PST) Received: from [192.168.1.173] (bras-base-kntaon1617w-grc-33-142-112-185-132.dsl.bell.ca. [142.112.185.132]) by smtp.googlemail.com with ESMTPSA id j8sm6040739ils.62.2021.11.22.04.45.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 22 Nov 2021 04:45:48 -0800 (PST) Message-ID: Date: Mon, 22 Nov 2021 07:45:46 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.1 Content-Language: en-US To: =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= , John Fastabend , Jesper Dangaard Brouer , "Karlsson, Magnus" , "Desouza, Ederson" References: <875ysqflg1.fsf@toke.dk> <61966ec0722fe_2f3212080@john.notmuch> <871r3cdwng.fsf@toke.dk> From: Jamal Hadi Salim In-Reply-To: <871r3cdwng.fsf@toke.dk> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Message-ID-Hash: MS6APR77BQMILNAITQSXM7467G6QMOIQ X-Message-ID-Hash: MS6APR77BQMILNAITQSXM7467G6QMOIQ X-MailFrom: jhs@mojatatu.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: brouer@redhat.com, "xdp-hints@xdp-project.net" , Eelco Chaudron , Andrii Nakryiko , "Fijalkowski, Maciej" , "Burakov, Anatoly" , tom Herbert X-Mailman-Version: 3.3.4 Precedence: list Subject: [xdp-hints] Basic/Dumb question WAS(Re: Re: XDP-hints via local BTF info List-Id: XDP hardware hints design discussion Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: And it goes something like this: Why does the metadata have to go in the DMA descriptors? Our experience with the XDP metadata is: you start accessing that there is a performance penalty (extra cache miss(es)). Why is the metadata not encapped as part of the data? We dont have MTU issues on receive since that is entirely a local matter; meaning the hardware can expand the packet as much as it wants within the boundaries of alloced DMA buffer space and XDP and any other subsystem (TC for example) can take advantage of the metadata. Then extracting metadata becomes a parser issue and you get rid of the extra cache misses. Another advantage is: If you make the metadata part the packet data (and appropriately handle MTU issues) you can pass it around as well to VMs, containers, other machines,etc We have done something along these lines using TC IFE, see: https://legacy.netdevconf.info/0.1/sessions/9.html The BTF aspect for discoverability is still of value. I am wondering if we can extend the IFE action to suck in some BTF info so we dont have to create new kernel code... cheers, jamal