Date: Tue, 10 Nov 1998 20:08:50 +1100 From: Bruce Evans <bde@zeta.org.au> To: bde@zeta.org.au, peter@netplex.com.au Cc: current@FreeBSD.ORG, jc@irbs.com, mike@smith.net.au, narvi@haldjas.folklore.ee, smp@FreeBSD.ORG Subject: Re: Dog Sloooow SMP Message-ID: <199811100908.UAA23868@godzilla.zeta.org.au>
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>> >How about 64 for the odd case that K7 actually materialises as promised >> >and people start putting them in dual motherboards? >> >> That would be almost twice as slow for CC=gcc. CC=egcs handles 64-bit >> bit tests better, especially for the low 32 bits. > >32 vs. 64 is almost irrelevant.. There's no limit to the number of 32 bit >variables that we can use with flags in them, so there's no reason why >we'd use a 64 bit variable in the first place. It's easier and potentially faster to keep all the flags in a single (scalar) variable. >However.. One thing that bugs me is that we presently can optimize out >code and tests for a runtime boost when compiled for a specific cpu. eg: >if we support 386 cpus, we test for whether we have an invlpg instruction >or not - but if we are not compiling with a 386 option then this code and >the test for >= 486 goes away. Attempt to keep compile-time options and tests when they make a difference. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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