Date: Mon, 29 Jan 1996 14:58:36 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: bde@zeta.org.au (Bruce Evans) Cc: dyson@freefall.freebsd.org, terry@lambert.org, current@freefall.freebsd.org Subject: Optimization topics Message-ID: <199601292158.OAA04701@phaeton.artisoft.com> In-Reply-To: <199601262317.KAA27798@godzilla.zeta.org.au> from "Bruce Evans" at Jan 27, 96 10:17:54 am
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With all the pipe optimization stuff and all the work I've been doing in the Windows95 kernel recently. it occurs to me that there might be room for some optimizations in FreeBSD that Microsoft totally buggered up in Windows95. Specifically, it should be possible to run FreeBSD with the unaligned access bit set to disallow unaligned access of word/dword/qword objects. At the very least, the kernel code should be clean of this cruft. In Windows95, some programmers apparently believe that adding 3 bytes to the end of a packed structure containing a byte followed by 20 longs means "align to a longword boundry" -- at least that's what the comments in the DDK header files say. Clearly, these people never ran their own code in a kernel debugger, or they simply failed to see the significance of unaligned access. Many of the problems derive from unaligned stacks being passed down to otherwise "correct" code. Fie. Maybe this is a direction that can be explored? Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
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