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Andi Kleen wrote: >> For me, when compiled with -O2, it results in >> >> 84 >> 88 >> 132 >> >> which basically says: a "rdtsc->rdtsc" is 84 cycles, putting a "pushfl" in >> between is another _4_ cycles, and putting a "popfl" in between is about >> another 48 cycles. >> > > This means we should definitely change restore_flags() to only STI, > never popf > sti is expensive as well; iirc just as expensive on most processors as popf, although I don't have hard numbers to back this up on hand. An _unlikely_ jcc + popf? is better than a sti, for sure, but a likely jcc+popf could cost more than a jcc+sti, depending on model. Zach - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org 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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