from slashdot, discussing the ia64 (itanium) architecture: Re:No FP in kernel?
by descubes on Thursday May 16, @05:38PM (Score:4, Informative) (#3532917) (User #35093 Info) http://home.earthlink.net/~descubes [ Neutral ] There are two reasons: 1/ The massive amount of FP state in IA-64 (128 FP registers). So the linux kernel is compiled in such a way that only some FP registers can be used by the compiler. This means that on kernel entry and exit, only those FP registers need to be saved/restored. Also, by software conventions, these FP registers are "scratch" (modified by a call), so the kernel needs not save/restore them on a system call (which is seen as a call by the user code) 2/ The "software assist" for some FP operations. For instance, the FP divide and square root are not completely implemented in hardware (it's actually dependent on the particular IA-64 implementation, so future chips may implement it). For corner cases such as overflow, underflow, infinites, etc, the processor traps ("floating-point software assist" or FPSWA trap). The IA-64 Linux kernel designers decided to not support FPSWA from the kernel itself, which means that you can't do a FP divide in the kernel. I suspect this is what is more problematic for the application in question (load balancer doing FP computations, probably has some divides in there...) _______________________________________________________________ Have big pipes? SourceForge.net is looking for download mirrors. We supply the hardware. You get the recognition. Email Us: [EMAIL PROTECTED] _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
