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Date:      Thu, 25 Feb 2021 15:19:25 +0100
From:      Marek Zarychta <zarychtam@plan-b.pwste.edu.pl>
To:        "Alexander V. Chernikov" <melifaro@ipfw.ru>, =?UTF-8?Q?Olivier_Cochard-Labb=c3=a9?= <olivier@freebsd.org>
Cc:        "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>
Subject:   Re: option FIB_ALGO and dpdk_lpm4
Message-ID:  <fb16b73f-72ed-6709-ad13-5ed09bbd3452@plan-b.pwste.edu.pl>
In-Reply-To: <2892341614202492@mail.yandex.ru>
References:  <5670cd9a-cd10-2b89-1347-97a6c817c50f@sentex.net> <8696072a-dc25-8eff-04fa-4d1db13bf5cc@plan-b.pwste.edu.pl> <3588111612809020@mail.yandex.ru> <53ef5715-42ce-aad0-9a8b-11d91a9891e3@plan-b.pwste.edu.pl> <301391612827263@mail.yandex.ru> <ecb75bc5-72fe-4583-8fe6-e0cb5347ae02@plan-b.pwste.edu.pl> <2642181612914660@mail.yandex.ru> <2951613086198@mail.yandex.ru> <b51320bb-d401-3d96-64a6-139f2c980ffa@plan-b.pwste.edu.pl> <7121614026888@mail.yandex.ru> <7056db64-2e7f-6ad8-54a3-59ff406061cf@plan-b.pwste.edu.pl> <CA%2Bq%2BTcqTh55fZbYQTt7giN-c9kL8iF28QDoaaF1vKXhyW6RsNA@mail.gmail.com> <2892341614202492@mail.yandex.ru>

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From: Marek Zarychta <zarychtam@plan-b.pwste.edu.pl>
To: "Alexander V. Chernikov" <melifaro@ipfw.ru>,
 =?UTF-8?Q?Olivier_Cochard-Labb=c3=a9?= <olivier@freebsd.org>
Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>
Message-ID: <fb16b73f-72ed-6709-ad13-5ed09bbd3452@plan-b.pwste.edu.pl>
Subject: Re: option FIB_ALGO and dpdk_lpm4
References: <5670cd9a-cd10-2b89-1347-97a6c817c50f@sentex.net>
 <8696072a-dc25-8eff-04fa-4d1db13bf5cc@plan-b.pwste.edu.pl>
 <3588111612809020@mail.yandex.ru>
 <53ef5715-42ce-aad0-9a8b-11d91a9891e3@plan-b.pwste.edu.pl>
 <301391612827263@mail.yandex.ru>
 <ecb75bc5-72fe-4583-8fe6-e0cb5347ae02@plan-b.pwste.edu.pl>
 <2642181612914660@mail.yandex.ru> <2951613086198@mail.yandex.ru>
 <b51320bb-d401-3d96-64a6-139f2c980ffa@plan-b.pwste.edu.pl>
 <7121614026888@mail.yandex.ru>
 <7056db64-2e7f-6ad8-54a3-59ff406061cf@plan-b.pwste.edu.pl>
 <CA+q+TcqTh55fZbYQTt7giN-c9kL8iF28QDoaaF1vKXhyW6RsNA@mail.gmail.com>
 <2892341614202492@mail.yandex.ru>
In-Reply-To: <2892341614202492@mail.yandex.ru>

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W dniu 24.02.2021 o=C2=A022:40, Alexander V. Chernikov pisze:
> 24.02.2021, 10:50, "Olivier Cochard-Labb=C3=A9" <olivier@freebsd.org>:
>> On Wed, Feb 24, 2021 at 1:22 AM Marek Zarychta <
>> zarychtam@plan-b.pwste.edu.pl> wrote:
>>
>>> =C2=A0>
>>>
>>> =C2=A0Please let me ask only one final question. Does adding:
>>>
>>> =C2=A0net.route.algo.inet.algo=3Ddpdk_lpm4
>>> =C2=A0net.route.algo.inet6.algo=3Ddpdk_lpm6
>>>
>>> =C2=A0to /etc/sysctl.conf make any sense? I see that right FIB_ALGO i=
s
>>> =C2=A0automatically picked up when the module is available.
>>
>> My understanding is the network stack will switch to the optimum algor=
ithm
>> regarding the number of routes installed.
>> cf "Automatic algorithm selection" chapter here:
>> https://reviews.freebsd.org/D27401
>>
>> So you don't need to set this sysctl.
> To add some points to Olivier's explanation:
> indeed, algorithm selection SHOULD happen automatically.
> Some things to keep in mind: when the BGP sessions flaps kernel routes =
may go from the full-view to near-zero and vice versa.
> In that case, automatic selection will switch to lockless_radix for the=
 range between 10..1000 routes (or similar). Lockless radix schedules reb=
uild for every change, so the speed of deleting/adding first 1k routes ma=
y be slower than expected.

Hello Olivier and Alexander,
thank you for explaining this. As far as I have tested setting this from
sysctl.conf works for current fib. So to avoid early switching of route
algorithms and speed up initial filling of route tables with 850k+ ip
routes and 100k+ ip6 routes I'll keep both those setting in
/etc/sysctl.conf.


--=20
Marek Zarychta


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