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authorAdhemerval Zanella <azanella@linux.vnet.ibm.com>2017-12-11 17:39:42 -0200
committerTulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com>2017-12-11 17:39:42 -0200
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powerpc: POWER8 memcpy optimization for cached memory
On POWER8, unaligned memory accesses to cached memory has little impact on performance as opposed to its ancestors. It is disabled by default and will only be available when the tunable glibc.tune.cached_memopt is set to 1. __memcpy_power8_cached __memcpy_power7 ============================================================ max-size=4096: 33325.70 ( 12.65%) 38153.00 max-size=8192: 32878.20 ( 11.17%) 37012.30 max-size=16384: 33782.20 ( 11.61%) 38219.20 max-size=32768: 33296.20 ( 11.30%) 37538.30 max-size=65536: 33765.60 ( 10.53%) 37738.40 * manual/tunables.texi (Hardware Capability Tunables): Document glibc.tune.cached_memopt. * sysdeps/powerpc/cpu-features.c: New file. * sysdeps/powerpc/cpu-features.h: New file. * sysdeps/powerpc/dl-procinfo.c [!IS_IN(ldconfig)]: Add _dl_powerpc_cpu_features. * sysdeps/powerpc/dl-tunables.list: New file. * sysdeps/powerpc/ldsodefs.h: Include cpu-features.h. * sysdeps/powerpc/powerpc32/power4/multiarch/init-arch.h (INIT_ARCH): Initialize use_aligned_memopt. * sysdeps/powerpc/powerpc64/dl-machine.h [defined(SHARED && IS_IN(rtld))]: Restrict dl_platform_init availability and initialize CPU features used by tunables. * sysdeps/powerpc/powerpc64/multiarch/Makefile (sysdep_routines): Add memcpy-power8-cached. * sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c: Add __memcpy_power8_cached. * sysdeps/powerpc/powerpc64/multiarch/memcpy.c: Likewise. * sysdeps/powerpc/powerpc64/multiarch/memcpy-power8-cached.S: New file. Reviewed-by: Rajalakshmi Srinivasaraghavan <raji@linux.vnet.ibm.com>
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diff --git a/manual/tunables.texi b/manual/tunables.texi
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@@ -319,6 +319,16 @@ the ones in @code{sysdeps/x86/cpu-features.h}.
This tunable is specific to i386 and x86-64.
@end deftp
+@deftp Tunable glibc.tune.cached_memopt
+The @code{glibc.tune.cached_memopt=[0|1]} tunable allows the user to
+enable optimizations recommended for cacheable memory. If set to
+@code{1}, @theglibc{} assumes that the process memory image consists
+of cacheable (non-device) memory only. The default, @code{0},
+indicates that the process may use device memory.
+
+This tunable is specific to powerpc, powerpc64 and powerpc64le.
+@end deftp
+
@deftp Tunable glibc.tune.cpu
The @code{glibc.tune.cpu=xxx} tunable allows the user to tell @theglibc{} to
assume that the CPU is @code{xxx} where xxx may have one of these values: