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benchtests: Restore the clock_gettime option 

commit 7621e38bf3
Author: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Date:   Tue Jan 29 17:43:45 2019 +0000

    Add generic hp-timing support

removed the clock_gettime option.  Restore the clock_gettime option for
some x86 CPUs on which value from RDTSC may not be incremented at a fixed
rate.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
H.J. Lu 2020-06-05 09:48:04 -07:00
parent f607047668
commit e52434a2e4
3 changed files with 17 additions and 2 deletions
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6
benchtests/Makefile
View File

@ -132,11 +132,17 @@ endif
CPPFLAGS-nonlib += -DDURATION=$(BENCH_DURATION) -D_ISOMAC CPPFLAGS-nonlib += -DDURATION=$(BENCH_DURATION) -D_ISOMAC
# Use clock_gettime to measure performance of functions. The default is
# to use the architecture-specific high precision timing instructions.
ifdef USE_CLOCK_GETTIME
CPPFLAGS-nonlib += -DUSE_CLOCK_GETTIME
else
# On x86 processors, use RDTSCP, instead of RDTSC, to measure performance # On x86 processors, use RDTSCP, instead of RDTSC, to measure performance
# of functions. All x86 processors since 2010 support RDTSCP instruction. # of functions. All x86 processors since 2010 support RDTSCP instruction.
ifdef USE_RDTSCP ifdef USE_RDTSCP
CPPFLAGS-nonlib += -DUSE_RDTSCP CPPFLAGS-nonlib += -DUSE_RDTSCP
endif endif
endif
DETAILED_OPT := DETAILED_OPT :=

7
benchtests/README
View File

@ -27,7 +27,12 @@ BENCH_DURATION.
The benchmark suite does function call measurements using architecture-specific The benchmark suite does function call measurements using architecture-specific
high precision timing instructions whenever available. When such support is high precision timing instructions whenever available. When such support is
not available, it uses clock_gettime (CLOCK_MONOTONIC). not available, it uses clock_gettime (CLOCK_MONOTONIC). One can force the
benchmark to use clock_gettime by invoking make as follows:
$ make USE_CLOCK_GETTIME=1 bench
Again, one must run `make bench-clean' before changing the measurement method.
On x86 processors, RDTSCP instruction provides more precise timing data On x86 processors, RDTSCP instruction provides more precise timing data
than RDTSC instruction. All x86 processors since 2010 support RDTSCP than RDTSC instruction. All x86 processors since 2010 support RDTSCP

6
benchtests/bench-timing.h
View File

@ -18,7 +18,11 @@
#undef attribute_hidden #undef attribute_hidden
#define attribute_hidden #define attribute_hidden
#include <hp-timing.h> #ifdef USE_CLOCK_GETTIME
# include <sysdeps/generic/hp-timing.h>
#else
# include <hp-timing.h>
#endif
#include <stdint.h> #include <stdint.h>
#define GL(x) _##x #define GL(x) _##x