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 > real-time operating system RTEMS from the head version at 2017-04-04 > to the head version of today. I noticed that some read-write locks are > replaced by a relatively new stuff called EPOCH(9). Is there some > background information available for this? The man page is a bit vague > and searching for something named epoch on the internet is not really > great. For example, what is the motivation for this change? How is > this related to read-copy-update (RCU)? > 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 configuration 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. -- 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 geschäftliche Mitteilung im Sinne des EHUG.
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