From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by mail.toke.dk (Postfix) with ESMTPS id 8BF3A8EB1A7 for ; Mon, 22 Nov 2021 14:59:28 +0100 (CET) Authentication-Results: mail.toke.dk; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=H942/wqD DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1637589565; 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: in-reply-to:in-reply-to:references:references; bh=uSrphB4Sl86995iJPfwHRoe0Qa8VLjF8DwSktgiWDBY=; b=H942/wqDWwRM5cIhAdX5cGL8EpPx/eD7OxJ+4+wc7hMvuPvYvnHFhLbehfn0kFv5WFG0mb giXYJidwChugCgkYnssfcyVCqUPSpIA/DRxgI4BZTVzmP8FEZKkNkRjw/JlbVeuZrPS49/ bCtss5m63A6q9kHBOFM8tXdfzZ+HXxo= Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-480--4ECMPkSM_qRjBlPT5MjgA-1; Mon, 22 Nov 2021 08:59:21 -0500 X-MC-Unique: -4ECMPkSM_qRjBlPT5MjgA-1 Received: by mail-ed1-f71.google.com with SMTP id c1-20020aa7c741000000b003e7bf1da4bcso14846385eds.21 for ; Mon, 22 Nov 2021 05:59:21 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=uSrphB4Sl86995iJPfwHRoe0Qa8VLjF8DwSktgiWDBY=; b=mscMo+TtCkVlm61ygNCO3WPT7KnesuM0zASaL9Jh0bcW968p/2px0gnG2hmIMFrYm+ /DwRpaRXeuT8v769AdBYuTk6Kzo+Ruqff+V+HW8F60/f+NIdefAhCexMsd9WogPhr9iE oUbwVcik4/xJJ6RQRxwLDNHcwcxI3S5yVFnk1Hy/rPFQ6nGS2f5i0OlR8o6VeVRJEsPf B2GDM+yf5XGh93CBdmqQWlA+HwF3zgDO+xSuKZ1sa2RcDohMidW0JWHtpzdXTdZh3D5/ pqVD4mtj5+B3pnqM2iL+8XJUNaYIPogC3xJ2lkgMhRbEzw8yTE0V9vRYLUI1AHWSQVU0 UhAw== X-Gm-Message-State: AOAM532hqMa65N82xObUvS988lCiLcNk1tEZiOJxl6vJSzLSP71KzcOh F3fEj7vKTVZwE1+iibUomw/nz5r+E3Z3xUp61aLSmbhdwJ9R2fu07gGi/JYTsn/V92RoTN/rAWl QCmYRWaKfqkx5/PfArdhg X-Received: by 2002:a17:906:fcc8:: with SMTP id qx8mr40354459ejb.370.1637589559486; Mon, 22 Nov 2021 05:59:19 -0800 (PST) X-Google-Smtp-Source: ABdhPJwKiqN6wiGkoYZxrI8UWKustE2N7PbLaUnxWDmtF8pwz+AklzxqddW6St5fRUifViPt6PYSyw== X-Received: by 2002:a17:906:fcc8:: with SMTP id qx8mr40354216ejb.370.1637589557849; Mon, 22 Nov 2021 05:59:17 -0800 (PST) Received: from alrua-x1.borgediget.toke.dk ([2a0c:4d80:42:443::2]) by smtp.gmail.com with ESMTPSA id co10sm4204227edb.83.2021.11.22.05.59.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Nov 2021 05:59:17 -0800 (PST) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 75CDB180270; Mon, 22 Nov 2021 14:59:16 +0100 (CET) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Jamal Hadi Salim , John Fastabend , Jesper Dangaard Brouer , "Karlsson, Magnus" , "Desouza, Ederson" In-Reply-To: References: <875ysqflg1.fsf@toke.dk> <61966ec0722fe_2f3212080@john.notmuch> <871r3cdwng.fsf@toke.dk> X-Clacks-Overhead: GNU Terry Pratchett Date: Mon, 22 Nov 2021 14:59:16 +0100 Message-ID: <87r1b8cmvf.fsf@toke.dk> MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=toke@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Message-ID-Hash: HN7VHQW3XOA3TLTZOUAH5FVD7C233447 X-Message-ID-Hash: HN7VHQW3XOA3TLTZOUAH5FVD7C233447 X-MailFrom: toke@redhat.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] Re: 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: Jamal Hadi Salim writes: > 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. Once the hardware learns how to do that, this is absolutely the direction we want to go in. But for existing stuff, the metadata is in the descriptor and needs to be translated somehow... -Toke