Messages in this thread | | | Date | Wed, 01 Oct 2014 09:17:26 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH v2 1/2] x86_64,entry: Filter RFLAGS.NT on entry from userspace |
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On 10/01/2014 09:04 AM, Andy Lutomirski wrote: > > Agner Fog's tables for Sandy Bridge have 9 uops for popf and > reciprocal throughput 18. sti isn't listed for Sandy Bridge or > anything similar, but cld is 3 uops with reciprocal throughput 4. > Also, popf accesses rsp, and the sysenter code is very heavy on stack > manipulation. >
It does a stack operation. Newer CPUs optimize stack accesses pretty heavily. That doesn't mean back-to-back push/pop are all that optimized, I wonder if it would help separating them. popf is unlikely to ever be all that fast.
-hpa
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