Commit a3eb97bd authored Apr 24, 2015 by Marcelo Tosatti Committed by Paolo Bonzini May 07, 2015

x86: kvmclock: drop rdtsc_barrier()



Drop unnecessary rdtsc_barrier(), as has been determined empirically,
see 057e6a8c for details.

Noticed by Andy Lutomirski.

Improves clock_gettime() by approximately 15% on
Intel i7-3520M @ 2.90GHz.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent d90e3a35

arch/x86/include/asm/pvclock.h

+0 −1

Original line number	Diff line number	Diff line
		@@ -86,7 +86,6 @@ unsigned __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src,
		offset = pvclock_get_nsec_offset(src);
		ret = src->system_time + offset;
		ret_flags = src->flags;
		rdtsc_barrier();

		*cycles = ret;
		*flags = ret_flags;

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