* Andi Kleen <[email protected]> wrote: > For i386 iirc Jeremy/Zach did the benchmarking and they settled on %fs > because it was faster for something (originally it was %gs too) yep. IIRC, some CPUs only optimize %fs because that's what Windows uses and leaves Linux with %gs out in the cold. There's also a performance penalty for overlapping segment use, if the segment cache is single entry only with an additional optimization for NULL [which just hides the segment cache]. But if it's good for unification we could switch that to %gs again on 32-bit. I was one of the people who advocated the use of the 'other' segment register, so that the hardware has less overlap, but clean and unified code trumps this concern. It shouldnt be an issue on reasonably modern CPUs anyway. Ingo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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