Date: Sun, 21 Sep 1997 23:05:20 -0600 (MDT) From: Nate Williams <nate@mt.sri.com> To: "Justin T. Gibbs" <gibbs@plutotech.com> Cc: 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: <199709220505.XAA29116@rocky.mt.sri.com> In-Reply-To: <199709220008.SAA29412@pluto.plutotech.com> References: <199709212210.PAA13470@freefall.freebsd.org> <199709220008.SAA29412@pluto.plutotech.com>
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> 2) New callout interface. This gives O(1) insertion and removal of > callouts and an O(hash chain length) amount of work to be performed > in softclock. ... > the O(n) hit on insertion and removal was painful. The networking > code is another area that may want to make heavier use of callouts > now that it is efficient to do so. If you are maintaining a driver > outside of the tree, or need to update a driver I missed, see the > timeout.9 man page for details on how the new interface works. For > those who want to read more about the new implementation, here's a > pointer to the original paper: > > http://www.cs.berkeley.edu/~amc/research/timer/ I just read the paper, and it's interesting, but they never give results based on what the kernel does now. Basically, it's pretty easy to say that registering/unregistering timers is now much faster, but given that things can take longer in softclock(), it's not obvious (at least to me) that this is a win overall, since we call softlock a *heck* of alot more than we register/de-register timeout/callouts. Does anyone have insight they're willing to share, since the author's did prove they accomplished what they set out to do, but it didn't really give me a warm-fuzzy that it would help improve performance. Nate
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