Date: Mon, 24 Apr 1995 23:50:04 -0700 (PDT) From: Julian Elischer <julian@ref.tfs.com> To: bde@zeta.org.au (Bruce Evans) Cc: terry@cs.weber.edu, toor@jsdinc.root.com, geli.com!rcarter@implode.root.com, hackers@FreeBSD.org, jkh@violet.berkeley.edu Subject: Re: benchmark hell.. Message-ID: <199504250650.XAA05638@ref.tfs.com> In-Reply-To: <199504250440.OAA15562@godzilla.zeta.org.au> from "Bruce Evans" at Apr 25, 95 02:40:21 pm
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> FreeBSD's low level context switching is faster than Linux's because > hardware tasking is not used. Perhaps there is a lot more bloat in > other layers of the context switching. (Yes, there is. E.g., calling > microtime() for each context switch is very expensive except on > Pentiums). microtime() has to be called so that FreeBSD can do better > timing statistics and scheduling than Linux. ) However, for real > processes, context switching is relatively rare, so small differences > (less than a factor of 2-10) in the speed of context switching don't > matter. Bill Jolitz actually recanted on this.. in 386BSD, he as used the LINUX scheme of the 386 built-in context switches.... he eventually decided the advantages outweighed the disadvantages.. I believe he decided that, in the big picture, the CISC operation was faster than the "do-it-yourself" version. > julian
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