Messages in this thread | | | Date | Mon, 12 Mar 2007 14:02:45 +0100 | From | "Joerg Roedel" <> | Subject | Re: [PATCH 4/4 TRY#3] optimize and simplify get_cycles_sync() |
| |
On Fri, Mar 09, 2007 at 08:10:03PM +0200, Avi Kivity wrote: > 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?
Does this macro exist? I couldn't found it in the current git tree. And the rdtscp macros in msr.h use the plain opcode too.
Regards, Joerg
-- Joerg Roedel Operating System Research Center AMD Saxony LLC & Co. KG
- 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/
| |