Date: Sun, 05 Apr 1998 15:18:17 +0200 From: Poul-Henning Kamp <phk@critter.freebsd.dk> To: Bruce Evans <bde@zeta.org.au> Cc: peter@netplex.com.au, smp@FreeBSD.ORG Subject: Re: more SMP stuff Message-ID: <7701.891782297@critter.freebsd.dk> In-Reply-To: Your message of "Sun, 05 Apr 1998 23:06:05 %2B1000." <199804051306.XAA05313@godzilla.zeta.org.au>
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In message <199804051306.XAA05313@godzilla.zeta.org.au>, Bruce Evans writes: >>>The scaling needs to be more robust since the h/w counter might be >>>slower than 10^6 hz. >> >>No, that is a design decision. Timecounter must be >= 1MHz. > >Why? The i8254 is only marginally faster than 1MHz. There's no >reason to expect a faster clock unless the CPU clock can be read. This is not NetBSD, we're looking at modern HW platforms, not needless and pointless generality... >>>It's used by my version of the floppy driver which calls microtime() >>>to timestamp certain events. >> >>before the i8254 is initialized ? > >In fdprobe(), before the i8254 is completely initialized. >>>I don't think I call nanotime() so early. My rtcintr() calls >>>nanotime() to gather statistics, and nanotime() was reentered. >>>I don't see any reentrancy problems. There will be one when >>>nanotime updates tc->nanotime like it should. >> >>No it shouldn't, I'm sorry but I cannot find a way where that makes >>fewer problems than it fixes... > >It is essential for POSIX.1 conformance and probably for `make' E.g., >the following shows chmod()+stat() sometimes updating the ctime of >a fifo apparently-before either is called. But the problem here is that the FS code uses the "cheap" version, not the correct version... They "shouldn't" do that... I can agree to update time_second in nanoµtime(), but not the tc->microtime & tc->nanotime, that is too expensive. -- Poul-Henning Kamp FreeBSD coreteam member phk@FreeBSD.ORG "Real hackers run -current on their laptop." "Drink MONO-tonic, it goes down but it will NEVER come back up!" To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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