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authorH.J. Lu <hjl.tools@gmail.com>2017-06-20 08:33:29 -0700
committerH.J. Lu <hjl.tools@gmail.com>2017-06-20 08:37:28 -0700
commit905947c30455bea5eed42cdffd771a11b1554f1d (patch)
treece9e6f9c47f9d1f5536a68fbd3244ed26a6d2387 /elf
parentbeb52f502f0477465313675d2a0fbf3962e130b8 (diff)
downloadglibc-905947c30455bea5eed42cdffd771a11b1554f1d.tar.gz
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.
Diffstat (limited to 'elf')
-rw-r--r--elf/dl-tunables.list16
1 files changed, 16 insertions, 0 deletions
diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list
index 41ce9afa28..3247d49b59 100644
--- a/elf/dl-tunables.list
+++ b/elf/dl-tunables.list
@@ -82,6 +82,22 @@ glibc {
type: UINT_64
env_alias: LD_HWCAP_MASK
default: HWCAP_IMPORTANT
+ }
+ ifunc {
+ type: STRING
+ security_level: SXID_IGNORE
+ }
+ x86_non_temporal_threshold {
+ type: SIZE_T
+ security_level: SXID_IGNORE
+ }
+ x86_data_cache_size {
+ type: SIZE_T
+ security_level: SXID_IGNORE
+ }
+ x86_shared_cache_size {
+ type: SIZE_T
+ security_level: SXID_IGNORE
}
}
}