tunables: Add IFUNC selection and cache sizes

The current IFUNC selection is based on microbenchmarks in glibc.  It
should give the best performance for most workloads.  But other choices
may have better performance for a particular workload or on the hardware
which wasn't available at the selection was made.  The environment
variable, GLIBC_TUNABLES=glibc.tune.ifunc=-xxx,yyy,-zzz...., can be used
to enable CPU/ARCH feature yyy, disable CPU/ARCH feature yyy and zzz,
where the feature name is case-sensitive and has to match the ones in
cpu-features.h.  It can be used by glibc developers to override the
IFUNC selection to tune for a new processor or improve performance for
a particular workload.  It isn't intended for normal end users.

NOTE: the IFUNC selection may change over time.  Please check all
multiarch implementations when experimenting.

Also, GLIBC_TUNABLES=glibc.tune.x86_non_temporal_threshold=NUMBER is
provided to set threshold to use non temporal store to NUMBER,
GLIBC_TUNABLES=glibc.tune.x86_data_cache_size=NUMBER to set data cache
size, GLIBC_TUNABLES=glibc.tune.x86_shared_cache_size=NUMBER to set
shared cache size.

	* elf/dl-tunables.list (tune): Add ifunc,
	x86_non_temporal_threshold,
	x86_data_cache_size and x86_shared_cache_size.
	* manual/tunables.texi: Document glibc.tune.ifunc,
	glibc.tune.x86_data_cache_size, glibc.tune.x86_shared_cache_size
	and glibc.tune.x86_non_temporal_threshold.
	* sysdeps/unix/sysv/linux/x86/dl-sysdep.c: New file.
	* sysdeps/x86/cpu-tunables.c: Likewise.
	* sysdeps/x86/cacheinfo.c
	(init_cacheinfo): Check and get data cache size, shared cache
	size and non temporal threshold from cpu_features.
	* sysdeps/x86/cpu-features.c [HAVE_TUNABLES] (TUNABLE_NAMESPACE):
	New.
	[HAVE_TUNABLES] Include <unistd.h>.
	[HAVE_TUNABLES] Include <elf/dl-tunables.h>.
	[HAVE_TUNABLES] (TUNABLE_CALLBACK (set_ifunc)): Likewise.
	[HAVE_TUNABLES] (init_cpu_features): Use TUNABLE_GET to set
	IFUNC selection, data cache size, shared cache size and non
	temporal threshold.
	* sysdeps/x86/cpu-features.h (cpu_features): Add data_cache_size,
	shared_cache_size and non_temporal_threshold.

1 files changed, 21 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/x86/dl-sysdep.c b/sysdeps/unix/sysv/linux/x86/dl-sysdep.c
new file mode 100644
index 0000000000..64eb0d7956
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86/dl-sysdep.c
@@ -0,0 +1,21 @@
+/* Operating system support for run-time dynamic linker.  X86 version.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+#include <sysdeps/x86/cpu-tunables.c>
+#include <sysdeps/unix/sysv/linux/dl-sysdep.c>