Date: Thu, 25 Sep 1997 07:47:14 +0200 (MET DST) From: Finn Arne Gangstad <finnag@guardian.no> To: "Justin T. Gibbs" <gibbs@plutotech.com> Cc: Archie Cobbs <archie@whistle.com>, current@FreeBSD.ORG Subject: Re: timeout management (was: Re: cvs commit: ...) Message-ID: <Pine.LNX.3.95.970925072713.29522A-100000@lucifer.guardian.no> In-Reply-To: <199709250512.XAA19962@pluto.plutotech.com>
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On Wed, 24 Sep 1997, Justin T. Gibbs wrote: > >Have you guys looked at the timer code in Linux? It basically is a small > >variation of this, which makes all operations O(1) for almost > >every timer. > > It looks like a 5 level hierarchical timing wheel to me. FreeBSD currently > has a one level timing wheel. Cascade_timers should enable interrupts > at deterministic intervals so that interrupts are defered a deterministic > amount of time. In 2.1.X it just grabs the timer spinlock. 2.0.X is pretty much set in stone really (the new timer code was actually put in in 2.1.23 i think, but applied to 2.0.30 for efficiency reasons). There was a lot of discussion on the kernel list about cascace_timers enabling timers now and then, in practice cascade_timers never move many timers so it's not really a problem, even less of a problem when it just grabs the timer lock. - Finn Arne
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