Messages in this thread | | | Date | Fri, 09 Mar 2007 20:10:03 +0200 | From | Avi Kivity <> | Subject | Re: [PATCH 4/4 TRY#3] optimize and simplify get_cycles_sync() |
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Joerg Roedel wrote: > From: Joerg Roedel <joerg.roedel@amd.com> > > This patch simplifies the get_cycles_sync() function by removing > the #ifdefs from it. Further it introduces an optimization for AMD > processors. There the RDTSCP instruction is used instead of CPUID;RDTSC > which is helpfull if the kernel runs as a KVM guest. Running as a guest > makes CPUID very expensive because it causes an intercept of the guest. > > > +#define RDTSCP ".byte 0x0f, 0x01, 0xf9" > + alternative_io_two("cpuid\nrdtsc", > + "rdtsc", X86_FEATURE_SYNC_RDTSC, > + ".byte 0x0f, 0x01, 0xf9", X86_FEATURE_RDTSCP, >
why not use the RDTSCP macro here?
-- Do not meddle in the internals of kernels, for they are subtle and quick to panic.
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