Date: Thu, 23 Aug 2018 10:39:45 +0200 From: Sebastian Huber <sebastian.huber@embedded-brains.de> To: FreeBSD <freebsd-hackers@freebsd.org> Subject: Re: epoch(9) background information? Message-ID: <3bfedcc3-0dae-7979-2bd4-da83f2c67e87@embedded-brains.de> In-Reply-To: <db397431-2c4c-64de-634a-20f38ce6a60e@embedded-brains.de> References: <db397431-2c4c-64de-634a-20f38ce6a60e@embedded-brains.de>
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On 21/08/18 14:33, Sebastian Huber wrote: > Hello, > > I update currently a port of the FreeBSD network stack, etc. to the=20 > real-time operating system RTEMS from the head version at 2017-04-04=20 > to the head version of today. I noticed that some read-write locks are=20 > replaced by a relatively new stuff called EPOCH(9). Is there some=20 > background information available for this? The man page is a bit vague=20 > and searching for something named epoch on the internet is not really=20 > great. For example, what is the motivation for this change? How is=20 > this related to read-copy-update (RCU)? > We used the FreeBSD network stack also on low-end targets=20 (uni-processor) such as MCF548x ColdFire, Atmel SAM V71, SPARC LEON,=20 etc. in current production environments (not legacy systems). The=20 introduction of lock-free data structures (Concurrency Kit) and this=20 epoch memory reclamation makes little sense on these targets (at least=20 from my point of view). However, FreeBSD has still the SMP configuration=20 option (sys/conf/options) which suggests that SMP is optional. Is a=20 uni-processor system something which is considered by the FreeBSD=20 community as a thing worth supporting or can I expect that this is an=20 exotic environment which will get less and less well supported in the=20 future? I just need some guidance so that I can better plan for future=20 FreeBSD baseline updates. --=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= .
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