On Saturday 11 November 2006 08:54, Jeremy Chadwick wrote: > The kernel itself _will not_ use any SSE or MMX operations when built. > This is because these optimisations are known to break the FreeBSD > kernel. This applies to all i386 architectures, and probably 64-bit > architectures too (not sure).
I think this is mainly because the kernel has no FPU context so you can't actually use any FPU operation (including SSE & MMX) without potentially trashing userland data. Also, the cost of saving/restoring the context is quite high so potential benefits are largely negated. (I could be wrong but the above is what I remember reading on various lists over the years :) -- Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C
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