An insane idea on reference counting [pdf]

http://epicsol.org/~misha/BSDCan-2014-lwref.pdf

by _kp6z • 12 years ago

58 25 12 years ago

epicsol.org

mmastrac2• 12 years ago

Is the RCU patent really still an issue?

gregkh3• 12 years ago

Why wouldn't it be?

shmerl• 12 years ago

Why is it patentable?

mmastrac2• 12 years ago

It must be getting close to expiry at this point -- wasn't it filed in the mid 90s?

EDIT:

I did a little digging and some calculations in the USPTO's horrible, horrible expiry calculator and the list of patents in wikipedia (which TBH, I haven't dug into to figure out how relevant they are but the list below is roughly ordered from "fundamental" to "interesting things you can do with RCU"):

http://www.google.com/patents/US5442758 -- should have expired last year

http://www.google.com/patents/US5608893 -- will expire very shortly, but is noted as "lapsed" due to non-payment of fees

http://www.google.com/patents/US5727209 -- will expire next year

https://www.google.com/patents/US6219690 -- this one will be a few more years

http://www.google.com/patents/US6886162 -- even longer

JoshTriplett2• 12 years ago

Is the RCU patent really still an issue?

Only for BSDs; RCU is free to use under LGPL and GPL.

(It was originally only usable under GPL. Later on, after Mathieu Desnoyers implemented a userspace version "liburcu", IBM granted permission to use RCU under LGPL to allow liburcu to use that license, making it more universally usable by arbitrary userspace software.)

colanderman• 12 years ago

If writes are infrequent and readers issuing atomic operations on the same word is expensive, why not use a set of read-write locks? Reader contention on any given lock would be amortized over the set; the cost is eaten by writers who must write-lock all the locks.

sbahra• 12 years ago

The work gleb is showing here pretty much looks to be proxy collection, which also has a whole parade of patents. An interesting mechanism with good performance characteristics is defined at http://concurrencykit.org/presentations/ebr.pdf and is easily pluggable into an RCU implementation.

citrin_ru• 12 years ago

Do you know more about this patents?

mzs• 12 years ago

Could something like tokens from dragonfly BSD be adapted in the way that Matt mentions:

http://lists.dragonflybsd.org/pipermail/kernel/2004-February...

An insane idea on reference counting [pdf]

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