GNU C Library 2.33 Released With HWCAPS To Load Optimized Libraries For Modern CPUs

Written by Michael Larabel in GNU on 1 February 2021 at 01:12 PM EST. 16 Comments
The GNU C Library 2.33 release is out today as expected. Exciting with this libc update is HWCAPS in making it easier to load optimized libraries for modern CPUs.

See that linked article from last week for more details but Glibc 2.33 but basically it allows the dynamic linker to load optimized versions of libraries within a glibc-hwcaps directory on the library search path. The HWCAPS correspond to the new x86_64 microarchitecture feature levels and there is similar support for POWER and s390x as well. This is exciting, pending sufficient adoption and usage of this HWCAPS functionality by software vendors to allow for more optimized libraries to automatically get picked up on modern processors without restricting the support for running on older CPUs as well. Red Hat has been working on the x86_64 microarchitecture feature levels and Glibc-HWCAPS over the past year with part of the motivation around allowing more AMD Zen optimizations.

Glibc 2.33 also brings other dynamic linker improvements, support for the RISC-V ISA on Linux running on 32-bit hardware, adding sys/platform/x86.h for providing query macros for x86 CPU features, several security fixes, and a number of bug fixes.

Glibc 2.33 can be downloaded from if you are building the GNU C Library yourself. Glibc 2.33 should be working its way into Ubuntu 21.04, Fedora 34, and other upcoming Linux distribution releases.
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