From owner-freebsd-hackers@freebsd.org Thu Aug 23 09:28:30 2018 Return-Path: Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id E7FE1108763A for ; Thu, 23 Aug 2018 09:28:29 +0000 (UTC) (envelope-from sebastian.huber@embedded-brains.de) Received: from dedi548.your-server.de (dedi548.your-server.de [85.10.215.148]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 80CB889EC4 for ; Thu, 23 Aug 2018 09:28:29 +0000 (UTC) (envelope-from sebastian.huber@embedded-brains.de) Received: from [78.46.172.3] (helo=sslproxy06.your-server.de) by dedi548.your-server.de with esmtpsa (TLSv1.2:DHE-RSA-AES256-GCM-SHA384:256) (Exim 4.85_2) (envelope-from ) id 1fslum-0004bs-1w; Thu, 23 Aug 2018 11:28:28 +0200 Received: from [82.135.62.35] (helo=mail.embedded-brains.de) by sslproxy06.your-server.de with esmtpsa (TLSv1.2:DHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1fslul-0000fz-Ru; Thu, 23 Aug 2018 11:28:27 +0200 Received: from localhost (localhost.localhost [127.0.0.1]) by mail.embedded-brains.de (Postfix) with ESMTP id B0E312A165C; Thu, 23 Aug 2018 11:28:30 +0200 (CEST) Received: from mail.embedded-brains.de ([127.0.0.1]) by localhost (zimbra.eb.localhost [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id 7LQbvG8gc5gt; Thu, 23 Aug 2018 11:28:29 +0200 (CEST) Received: from localhost (localhost.localhost [127.0.0.1]) by mail.embedded-brains.de (Postfix) with ESMTP id 59FA32A167F; Thu, 23 Aug 2018 11:28:29 +0200 (CEST) X-Virus-Scanned: amavisd-new at zimbra.eb.localhost Received: from mail.embedded-brains.de ([127.0.0.1]) by localhost (zimbra.eb.localhost [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id xo8OZYaN73BW; Thu, 23 Aug 2018 11:28:29 +0200 (CEST) Received: from [192.168.96.149] (unknown [192.168.96.149]) by mail.embedded-brains.de (Postfix) with ESMTPSA id 26E222A165C; Thu, 23 Aug 2018 11:28:29 +0200 (CEST) Subject: Re: epoch(9) background information? To: Eugene Grosbein , FreeBSD References: <3bfedcc3-0dae-7979-2bd4-da83f2c67e87@embedded-brains.de> <5B7E7804.4030907@grosbein.net> From: Sebastian Huber Message-ID: <978ae736-89b9-6d83-e2a1-d2834ca8ae55@embedded-brains.de> Date: Thu, 23 Aug 2018 11:28:25 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <5B7E7804.4030907@grosbein.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: quoted-printable X-Authenticated-Sender: smtp-embedded@poldinet.de X-Virus-Scanned: Clear (ClamAV 0.100.1/24865/Thu Aug 23 07:52:53 2018) X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.27 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 23 Aug 2018 09:28:30 -0000 On 23/08/18 11:01, Eugene Grosbein wrote: > On 23.08.2018 15:39, Sebastian Huber wrote: > >> We used the FreeBSD network stack also on low-end targets >> (uni-processor) such as MCF548x ColdFire, Atmel SAM V71, SPARC LEON, >> etc. in current production environments (not legacy systems). The >> introduction of lock-free data structures (Concurrency Kit) and this >> epoch memory reclamation makes little sense on these targets (at least >> from my point of view). However, FreeBSD has still the SMP configurati= on >> option (sys/conf/options) which suggests that SMP is optional. Is a >> uni-processor system something which is considered by the FreeBSD >> community as a thing worth supporting or can I expect that this is an >> exotic environment which will get less and less well supported in the >> future? I just need some guidance so that I can better plan for future >> FreeBSD baseline updates. > FreeBSD as virtualized uniprocessor guest should be supported at full s= cale, > as well as embedded applications using single core x86 and non-x86 CPUs= . If something should be supported, then there must be also someone who=20 ensures that this is actually the case. I don't know the FreeBSD=20 community good enough to judge if there is sufficient=20 manpower/funding/interest for a well supported uni-processor FreeBSD.=20 From the commits it is clear that FreeBSD receives a lot of attention=20 from CDN providers such as Netflix and Limelight Networks. They probably=20 don't care about uni-processor system support at all. The use of=20 lock-free data structures (Concurrency Kit) and the epoch memory=20 reclamation are now a mandatory infrastructure. There is no FreeBSD=20 configuration option to avoid this. The Concurrency Kit in sys/contrib/ck has no explicit support for the=20 FreeBSD RISC-V and MIPS architectures. So, I guess the fall-back=20 sys/contrib/ck/include/gcc/ck_pr.h is used. The atomic support in=20 sys/contrib/ck partially duplicates/extends the general atomic support=20 of the FreeBSD kernel ATOMIC(9). To me it is a bit unclear what will be=20 the future direction in the FreeBSD kernel with respect to lock-free=20 data structures. --=20 Sebastian Huber, embedded brains GmbH Address : Dornierstr. 4, D-82178 Puchheim, Germany Phone : +49 89 189 47 41-16 Fax : +49 89 189 47 41-09 E-Mail : sebastian.huber@embedded-brains.de PGP : Public key available on request. Diese Nachricht ist keine gesch=C3=A4ftliche Mitteilung im Sinne des EHUG= .