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Behavior of the GNU C Library can be tuned to assume specific hardware capabilities
by setting the following tunables in the tune namespace:
This tunable supersedes the LD_HWCAP_MASK environment variable and is
identical in features.
The AT_HWCAP key in the Auxiliary Vector specifies instruction set
extensions available in the processor at runtime for some architectures. The
glibc.tune.hwcap_mask tunable allows the user to mask out those
capabilities at runtime, thus disabling use of those extensions.
The glibc.tune.hwcaps=-xxx,yyy,-zzz... tunable allows the user to
enable CPU/ARCH feature yyy, disable CPU/ARCH feature xxx
and zzz where the feature name is case-sensitive and has to match
the ones in sysdeps/x86/cpu-features.h.
This tunable is specific to i386 and x86-64.
The glibc.tune.cached_memopt=[0|1] tunable allows the user to
enable optimizations recommended for cacheable memory. If set to
1, the GNU C Library assumes that the process memory image consists
of cacheable (non-device) memory only. The default, 0,
indicates that the process may use device memory.
This tunable is specific to powerpc, powerpc64 and powerpc64le.
The glibc.tune.cpu=xxx tunable allows the user to tell the GNU C Library to
assume that the CPU is xxx where xxx may have one of these values:
generic, falkor, thunderxt88, thunderx2t99,
thunderx2t99p1.
This tunable is specific to aarch64.
The glibc.tune.x86_data_cache_size tunable allows the user to set
data cache size in bytes for use in memory and string routines.
This tunable is specific to i386 and x86-64.
The glibc.tune.x86_shared_cache_size tunable allows the user to
set shared cache size in bytes for use in memory and string routines.
The glibc.tune.x86_non_temporal_threshold tunable allows the user
to set threshold in bytes for non temporal store.
This tunable is specific to i386 and x86-64.
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