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 23B1199E61C
for <xdp-hints@xdp-project.net>; Fri, 9 Sep 2022 10:12:49 +0200 (CEST)
Authentication-Results: mail.toke.dk;
dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=ORn4ONPo
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com;
s=mimecast20190719; t=1662711168;
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=w1aljE3uZPlufePUzO0o5QnlpqVItqq0OhrVapvAOQE=;
b=ORn4ONPoKzRl8RKCXk43LyULbiZhXGf2brbja8nceSeAEmwy0Nej1/ubdYUFtl3xYQSDYa
cvL65xoRkO+3wfTJ/fCYCQzW7KzFnGgqLeF+YWzFDcAFF5hqFw/tL4/2NbkIwYfshB5oiF
Ksr/LT3vdPjHkuPA+/rmT8NQLicLwIE=
Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com
[209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS
(version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id
us-mta-518-mWSQUytOM8qsX94SjOhetg-1; Fri, 09 Sep 2022 04:12:41 -0400
X-MC-Unique: mWSQUytOM8qsX94SjOhetg-1
Received: by mail-wm1-f71.google.com with SMTP id h4-20020a1c2104000000b003b334af7d50so1811514wmh.3
for <xdp-hints@xdp-project.net>; Fri, 09 Sep 2022 01:12:40 -0700 (PDT)
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
d=1e100.net; s=20210112;
h=content-transfer-encoding:in-reply-to:from:references:cc:to
:content-language:subject:user-agent:mime-version:date:message-id
:x-gm-message-state:from:to:cc:subject:date;
bh=w1aljE3uZPlufePUzO0o5QnlpqVItqq0OhrVapvAOQE=;
b=L4zYFLGGzmIshIxXiTd5oCHctV+HRuOu4ZjDjLCWSUM4p0vqjmvAvm0EFQogKpot9C
Nf3OIDv58j5h1vhLvHIml1C1XVyTcpEv6otC2Q25yBRSFRGGvEo9OP/YpvSA3JWzoqKi
+pYGi92W707PpiyhLF3ujwo6XYH2sxLsyVzMV3O+sb6OPzhoTIsQDC+NFNKZRCRrZwS7
uib+hwhvF732S76jAa+9nCJLnmk+NM8k1nGVbudJbB8QnIA/yltBfmQJSdB0FXXMCcH2
LKltyqw2veTe34NCD86jWw55bjvUtCabCWwnx0Is5q3i2+Xx+eH2TFy7R5iLRjbXoisG
z2yA==
X-Gm-Message-State: ACgBeo3Xs07TLOCfpRD6Okd3Bp6YVTdheZeBAceF1mH+INecyhXXuj84
LoR929OlrZ+SjHP/sqpl7t1eCSoVICah0K17HeayiZCJXLb3LPbf+P7zTsEnWCcPRj3GBKTYNfE
OG124cTgcdaKkZarCb/Kq
X-Received: by 2002:a05:6000:178d:b0:226:ffe8:72df with SMTP id e13-20020a056000178d00b00226ffe872dfmr7007123wrg.496.1662711160070;
Fri, 09 Sep 2022 01:12:40 -0700 (PDT)
X-Google-Smtp-Source: AA6agR6GbqXE9LDoUcwdJx+L6WAX5Qhcp4f5VOTBbdcg+7QT8tyP64NbNXEg6EPqcjB/DNWdFfFwDA==
X-Received: by 2002:a05:6000:178d:b0:226:ffe8:72df with SMTP id e13-20020a056000178d00b00226ffe872dfmr7007109wrg.496.1662711159833;
Fri, 09 Sep 2022 01:12:39 -0700 (PDT)
Received: from [192.168.0.4] ([78.17.187.218])
by smtp.gmail.com with ESMTPSA id z2-20020a05600c0a0200b003a5c244fc13sm6247863wmp.2.2022.09.09.01.12.39
(version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128);
Fri, 09 Sep 2022 01:12:39 -0700 (PDT)
Message-ID: <e1ab2141-03cc-f97c-3788-59923a029203@redhat.com>
Date: Fri, 9 Sep 2022 09:12:38 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0)
Gecko/20100101 Thunderbird/102.2.1
To: Magnus Karlsson <magnus.karlsson@gmail.com>,
Jesper Dangaard Brouer <jbrouer@redhat.com>
References: <166256538687.1434226.15760041133601409770.stgit@firesoul>
<166256558657.1434226.7390735974413846384.stgit@firesoul>
<CAJ8uoz3UcC2tnMtG8W6a3HpCKgaYSzSCqowLFQVwCcsr+NKBOQ@mail.gmail.com>
<b5f0d10d-2d4e-34d6-1e45-c206cb6f5d26@redhat.com>
<9aab9ef1-446d-57ab-5789-afffe27801f4@redhat.com>
<CAJ8uoz0CD18RUYU4SMsubB8fhv3uOwp6wi_uKsZSu_aOV5piaA@mail.gmail.com>
From: Maryam Tahhan <mtahhan@redhat.com>
In-Reply-To: <CAJ8uoz0CD18RUYU4SMsubB8fhv3uOwp6wi_uKsZSu_aOV5piaA@mail.gmail.com>
X-Mimecast-Spam-Score: 0
X-Mimecast-Originator: redhat.com
Content-Language: en-US
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Message-ID-Hash: ZXMBBO7AH5HBNWGCAWKVPEGDBVGW3SL7
X-Message-ID-Hash: ZXMBBO7AH5HBNWGCAWKVPEGDBVGW3SL7
X-MailFrom: mtahhan@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, bpf@vger.kernel.org, netdev@vger.kernel.org, xdp-hints@xdp-project.net, larysa.zaremba@intel.com, memxor@gmail.com, Lorenzo Bianconi <lorenzo@kernel.org>, Alexei Starovoitov <alexei.starovoitov@gmail.com>, Daniel Borkmann <borkmann@iogearbox.net>, Andrii Nakryiko <andrii.nakryiko@gmail.com>, dave@dtucker.co.uk, Magnus Karlsson <magnus.karlsson@intel.com>, bjorn@kernel.org
X-Mailman-Version: 3.3.5
Precedence: list
Subject: [xdp-hints] Re: [PATCH RFCv2 bpf-next 17/18] xsk: AF_XDP xdp-hints support in desc options
List-Id: XDP hardware hints design discussion <xdp-hints.xdp-project.net>
Archived-At: <https://lists.xdp-project.net/xdp-hints/e1ab2141-03cc-f97c-3788-59923a029203@redhat.com/>
List-Archive: <https://lists.xdp-project.net/xdp-hints/>
List-Help: <mailto:xdp-hints-request@xdp-project.net?subject=help>
List-Owner: <mailto:xdp-hints-owner@xdp-project.net>
List-Post: <mailto:xdp-hints@xdp-project.net>
List-Subscribe: <mailto:xdp-hints-join@xdp-project.net>
List-Unsubscribe: <mailto:xdp-hints-leave@xdp-project.net>
<snip>
>>>>
>>>> * Instead encode this information into each metadata entry in the
>>>> metadata area, in some way so that a flags field is not needed (-1
>>>> signifies not valid, or whatever happens to make sense). This has the
>>>> drawback that the user might have to look at a large number of entries
>>>> just to find out there is nothing valid to read. To alleviate this, it
>>>> could be combined with the next suggestion.
>>>>
>>>> * Dedicate one bit in the options field to indicate that there is at
>>>> least one valid metadata entry in the metadata area. This could be
>>>> combined with the two approaches above. However, depending on what
>>>> metadata you have enabled, this bit might be pointless. If some
>>>> metadata is always valid, then it serves no purpose. But it might if
>>>> all enabled metadata is rarely valid, e.g., if you get an Rx timestamp
>>>> on one packet out of one thousand.
>>>>
>>
>> I like this option better! Except that I have hoped to get 2 bits ;-)
>
> I will give you two if you need it Jesper, no problem :-).
>
Ok I will look at implementing and testing this and post an update.
Thanks folks
>> The performance advantage is that the AF_XDP descriptor bits will
>> already be cache-hot, and if it indicates no-metadata-hints the AF_XDP
>> application can avoid reading the metadata cache-line :-).
>
> Agreed. I prefer if we can keep it simple and fast like this.
>
<snip>