Date: Fri, 13 Dec 1996 05:51:44 -0500 (EST) From: Peter Dufault <dufault@hda.com> To: bakul@plexuscom.com (Bakul Shah) Cc: michaelh@cet.co.jp, Hackers@freebsd.org Subject: Re: Implementing atomic DCAS on Intel for NBS Message-ID: <199612131051.FAA12751@hda.hda.com> In-Reply-To: <199612130653.BAA17932@chai.plexuscom.com> from Bakul Shah at "Dec 13, 96 01:53:31 am"
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> Comments about NBS: > > In general, when the number of words read exceeds the number of > written words (for shared data structures), NBS will be more > efficient than lockIng. Deadlock simply can not happen because > atmost there is just one shared lock. That one shared lock will get pretty busy, while with standard locking the lock activity can "page" to a point in an MP hierarchy where they are actually used. I'll have to look up the references to see how this locality issue is discussed. Language support with some kind of commit operation on data structures seems attractive - by this I mean only declaring those parts of a data structure that must be lockable lockable, and automatically getting write accesses nCAS'd where the system would update all fields at once from a temporary (together with the serial number update - go easy on this - I haven't thought about it much yet). -- Peter Dufault (dufault@hda.com) Real-Time Machine Control and Simulation HD Associates, Inc. Voice: 508 433 6936
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