2.13.1 Build Configuration ¶

By default, the build enables hardware acceleration detection for all supported features. This applies to both the accelerated code used internally within coreutils and the accelerated code used in external libraries.

The detection performed internally within coreutils can be overridden at build time using various configure variables, which currently include:

‘gl_cv_crc_pclmul’

‘utils_cv_avx2_intrinsic_exists’

‘utils_cv_avx2_pclmul_intrinsic_exists’

‘utils_cv_avx512_pclmul_intrinsic_exists’

‘utils_cv_pclmul_intrinsic_exists’

‘utils_cv_vmull_intrinsic_exists’

External library detection is automatic for OpenSSL, so you must use the ‘--with-openssl=no’ configure option to disable this if desired. Conversely, the Linux kernel cryptographic API is not used automatically and must be explicitly enabled with the ‘--with-linux-crypto’ configure option.

2.13.2 Runtime Configuration ¶

The usual method for runtime configuration of hardware detection is through environment variables, since you typically want to configure hardware interactions quite broadly. Note that these environment variables are not specific to coreutils, but coreutils will honor them when set.

For example, the following environment settings would disable hardware acceleration both within coreutils and in libcrypto (if used) on x86_64, ARM, and AArch64 platforms:

export OPENSSL_ia32cap='0x0'
export OPENSSL_armcap='0x0'
export GLIBC_TUNABLES='glibc.cpu.hwcaps=-AVX512F,-AVX2,-AVX,-PMULL'

The --debug option is available on all utilities supporting hardware acceleration and will report the current acceleration mode in use. For example:

$ wc -l --debug /dev/null >/dev/null
wc: using avx2 hardware support

$ cksum --debug /dev/null >/dev/null
cksum: avx512 support not detected
cksum: avx2 support not detected
cksum: using pclmul hardware support