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-rw-r--r--benchtests/README9
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diff --git a/benchtests/README b/benchtests/README
index 4ddff794d1..aaf0b659e2 100644
--- a/benchtests/README
+++ b/benchtests/README
@@ -34,6 +34,15 @@ the benchmark to use clock_gettime by invoking make as follows:
 
 Again, one must run `make bench-clean' before changing the measurement method.
 
+On x86 processors, RDTSCP instruction provides more precise timing data
+than RDTSC instruction.  All x86 processors since 2010 support RDTSCP
+instruction.  One can force the benchmark to use RDTSCP by invoking make
+as follows:
+
+  $ make USE_RDTSCP=1 bench
+
+One must run `make bench-clean' before changing the measurement method.
+
 Running benchmarks on another target:
 ====================================