Date: Tue, 21 Aug 2018 09:38:03 -0400 From: Jacques Fourie <jacques.fourie@gmail.com> To: Sebastian Huber <sebastian.huber@embedded-brains.de> Cc: FreeBSD <freebsd-hackers@freebsd.org> Subject: Re: epoch(9) background information? Message-ID: <CALX0vxBAN6nckuAnYR3_mOfwbCjJCjHGuuOFh9njpxO%2BGUzo3w@mail.gmail.com> 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 Tue, Aug 21, 2018 at 8:33 AM, Sebastian Huber < sebastian.huber@embedded-brains.de> 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 t= he > 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 exampl= e, > what is the motivation for this change? How is this related to > read-copy-update (RCU)? > > -- > Sebastian Huber, embedded brains GmbH > > Address : Dornierstr. 4, D-82178 Puchheim, Germany > <https://maps.google.com/?q=3DDornierstr.+4,+D-82178+Puchheim,+Germany&en= try=3Dgmail&source=3Dg> > 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= . > > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org= " > Additional information is available here : http://concurrencykit.org/pr esentations/ebr.pdf. The way I understand it is that it is mostly used in place of read locks to provide liveness guarantees without using atomics. Additional detail is available in the commit messages. As an example see r333813 for some performance data.
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