Date: Tue, 8 Aug 2006 18:24:23 +0200 From: "Attilio Rao" <attilio@freebsd.org> To: "Suleiman Souhlal" <ssouhlal@freebsd.org> Cc: freebsd-current@freebsd.org, freebsd-arch@freebsd.org Subject: Re: [PATCH] Adding Solaris-style "owner of records" to rwlocks Message-ID: <3bbf2fe10608080924p1536b4e5s6d3c79be3546aefe@mail.gmail.com> In-Reply-To: <3bbf2fe10608080908l3c8e7c3aq1e65a610d76d189b@mail.gmail.com> References: <3bbf2fe10608071227j17c4cfa6qd84e1d8e53668fda@mail.gmail.com> <44D7B7ED.5070302@FreeBSD.org> <3bbf2fe10608080908l3c8e7c3aq1e65a610d76d189b@mail.gmail.com>
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2006/8/8, Attilio Rao <attilio@freebsd.org>: > > > > Aren't you missing the hard part: transferring ownership from one reader > > to another? If you don't, you'll still have priority inversions as soon > > as the initial reader unlocks.. > > Exactly, but having a complete owner switching would be: > 1) too hard to achieve in terms of resource taken > 2) will imply too many races and we might get a too hard function > > With this implementation, only the first rlock (for every class > contention) will be penalyzed while the other are treacted as the > easy/hard case. > It doesn't completely solve the priority inversion problem, but it's > the better compromise between performances/correctnes. As addiction, I can say it would be interesting investigate other solutions (i.e: partial readers tracking or full readers tracking) and benchmarking what works in the better way, but here benchmarks would take the biggest part of time. If somebody is interested can drop a mail to me (or to John, if he has time). Attilio -- Peace can only be achieved by understanding - A. Einstein
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