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| author | H.J. Lu <hjl.tools@gmail.com> | 2018-10-24 02:19:15 -0700 |
|---|---|---|
| committer | H.J. Lu <hjl.tools@gmail.com> | 2018-10-24 02:19:34 -0700 |
| commit | 7cc65773f04e0f4252428c40dcbb784a39b58cd1 (patch) | |
| tree | 8ab811df64ea1c81daac9b4e8b645ea3998acf08 /benchtests | |
| parent | 18ad0de6513bf8a8e4ba757c069e6806d07920f8 (diff) | |
| download | glibc-7cc65773f04e0f4252428c40dcbb784a39b58cd1.zip glibc-7cc65773f04e0f4252428c40dcbb784a39b58cd1.tar.gz glibc-7cc65773f04e0f4252428c40dcbb784a39b58cd1.tar.bz2 | |
x86: Support RDTSCP for benchtests
RDTSCP waits until all previous instructions have executed and all
previous loads are globally visible before reading the counter. RDTSC
doesn't wait until all previous instructions have been executed before
reading the counter. All x86 processors since 2010 support RDTSCP
instruction. This patch adds RDTSCP support to benchtests.
* benchtests/Makefile (CPPFLAGS-nonlib): Add -DUSE_RDTSCP if
USE_RDTSCP is defined.
* sysdeps/x86/hp-timing.h (HP_TIMING_NOW): Use RDTSCP if
USE_RDTSCP is defined.
Diffstat (limited to 'benchtests')
| -rw-r--r-- | benchtests/Makefile | 6 | ||||
| -rw-r--r-- | benchtests/README | 9 |
2 files changed, 15 insertions, 0 deletions
diff --git a/benchtests/Makefile b/benchtests/Makefile index bcd6a9c..45aeb5f 100644 --- a/benchtests/Makefile +++ b/benchtests/Makefile @@ -131,6 +131,12 @@ CPPFLAGS-nonlib += -DDURATION=$(BENCH_DURATION) -D_ISOMAC # HP_TIMING if it is available. ifdef USE_CLOCK_GETTIME CPPFLAGS-nonlib += -DUSE_CLOCK_GETTIME +else +# On x86 processors, use RDTSCP, instead of RDTSC, to measure performance +# of functions. All x86 processors since 2010 support RDTSCP instruction. +ifdef USE_RDTSCP +CPPFLAGS-nonlib += -DUSE_RDTSCP +endif endif DETAILED_OPT := diff --git a/benchtests/README b/benchtests/README index 4ddff79..aaf0b65 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: ==================================== |