Date: Mon, 22 Sep 1997 15:04:20 -0600 From: "Justin T. Gibbs" <gibbs@plutotech.com> To: Nate Williams <nate@mt.sri.com> Cc: "Justin T. Gibbs" <gibbs@plutotech.com>, Bruce Evans <bde@zeta.org.au>, current@freebsd.org Subject: Re: cvs commit: src/sys/conf files src/sys/dev/vx if_vx.c if_vxreg.h src/sys/i386/apm apm.c src/sys/i386/conf GENERIC files.i386 src/sys/i386/eisa 3c5x9.c aha1742.c aic7770.c bt74x.c eisaconf.c eisaconf.h if_fea.c if_vx_eisa.c src/sys/i386/i386 autoconf.c ... Message-ID: <199709222104.PAA01993@pluto.plutotech.com> In-Reply-To: Your message of "Mon, 22 Sep 1997 14:46:57 MDT." <199709222046.OAA02778@rocky.mt.sri.com>
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>> The timeout and untimeout calls do not need to be paired for this to be >> the case. > >Sure they do. If you have a bunch of timeout calls, and the untimeouts >for them don't occur until *after* softclock, you have lots of entries >to walk through. And timeout and untimeout would have just as many (most likely more since the hash table isn't very full) to walk through each time. I was comparing the new softclock with time O(n) (which is worse than it really is) and that of the original timeout and untimeout, O(n). The calls don't need to be paired for this analysis to be valid. >> But what is in the list if few callouts are outstanding? > >The whole assumption of this code is that the frequency of paird >timeout/untimeout calls happen *much* more frequently than the frequency >of softclocks, right? If that isn't the case (the clock frequency is >increased, or timeouts are long), then the new system is a lose, because >the # of callouts in the list at softclock() time starts to effect the >effeciency of the system. > >Is this a correct assumption? If so, then Terry's concerns about >high-resolution timers is still valid, even though the design wasn't >designed for this, it negatively affects it *IF* high-resolution timers >are a future goal. The code assumes nothing of the sort. My analysis of running time assumes that the frequency of calls to timeout or untimeout is >= the number of calls to softclock. If we decide to do high resolution timers, the analysis may change as will most likely the implementation although probably not by much. >Nate -- Justin T. Gibbs =========================================== FreeBSD: Turning PCs into workstations ===========================================
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