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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
commitc9cd7b0ce5c52a3dac7347084651d7df0b39a6d0 (patch)
tree725d9e24e8a3c66866e2b8963928d4857f09b561 /manual
parente70c6fee466d26af36a38270e451cbe3273a6660 (diff)
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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>
Diffstat (limited to 'manual')
-rw-r--r--manual/tunables.texi10
1 files changed, 10 insertions, 0 deletions
diff --git a/manual/tunables.texi b/manual/tunables.texi
index e851b95c59..6e0ee28980 100644
--- a/manual/tunables.texi
+++ b/manual/tunables.texi
@@ -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: