--- On Tue, 9/15/09, peterjer...@acm.org <peterjer...@acm.org> wrote:
> From: peterjer...@acm.org <peterjer...@acm.org> > Subject: Re: [POLLING] strange interrupt/system load > To: "Barney Cordoba" <barney_cord...@yahoo.com> > Cc: freebsd-net@freebsd.org > Date: Tuesday, September 15, 2009, 3:38 AM > On 2009-Sep-13 07:19:24 -0700, Barney > Cordoba <barney_cord...@yahoo.com> > wrote: > >64bits must be faster than 32bits is patently > misguided. My rule of > >thumb is that if I don't need 64bits for something, I > avoid it. > > It's not quite that cut-and-dry. The 64-bit ISA is > significantly > different to the 32-bit ISA and has different subroutine > calling > conventions. Yes, you do need to lug 64-bit pointers > around but the > overall codesize is comparable (looking at /usr/bin and > /lib suggests > about a 5% increase in size going from i386 to amd64) - a > lot of this > is probably because amd64 has a 16-bit offset mode so > there's much > less need for 32-bit offsets. Having twice as many > registers is a > win in some areas (less spilling to memory) and a loss in > others (more > state to save/restore on a context switch). > > If performance is critical, it's probably worthwhile > benchmarking > both i386 and amd64 variants and seeing which works best > for you. > "Rules of Thumb" are generally for those times when you don't have a pressing preference and you don't want to spend your life endlessly benchmarking. I don't think its the code, necessarity, but rather the significant increase in the size of data structures, and the memory that has to be moved around. I haven't tried with the latest compiler but I can't see why it would have any benefit for systems used for high capacity networking other than incrementing counters. Barney _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
