GNU C Library 2.44 released [LWN.net]

Version 2.44 of the GNU C Library has been released. Changes include a new /etc/tunables.conf file for the system-wide setting of tunable parameters, a new tunable to control the use of transparent huge pages for read-only executable segments, a number of math-function improvements, a handful of security fixes, and more.

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Overhead?

Posted Jul 30, 2026 23:35 UTC (Thu) by mirabilos (subscriber, #84359) [Link] (4 responses)

So, does that mean that every program compiled with glibc now does an open (and if it succeeds, read and close) more during startup?

Ouch.

OpenBSD at least put the malloc.conf contents into the symlink target, but…

Overhead?

Posted Jul 31, 2026 0:15 UTC (Fri) by neilbrown (subscriber, #359) [Link] (3 responses)

The linked release notes say:

System-wide tunables can be applied using /etc/tunables.conf and running ldconfig.

so it looks like the answer is "no", it doesn't open another file during process startup.

Overhead?

Posted Jul 31, 2026 0:20 UTC (Fri) by mirabilos (subscriber, #84359) [Link] (2 responses)

… ah, so it’s moving files around?

Or converting that to a secret symlink somewhere so it reduces to one readlink syscall?

Overhead?

Posted Jul 31, 2026 1:21 UTC (Fri) by neilbrown (subscriber, #359) [Link] (1 responses)

It is reading /etc/tunables.conf when you run ldconfig, parsing it, and storing the data in as new section in /etc/ld.so.cache, which is already loaded whenever any process starts. So when /etc/tunables.conf doesn't exist, the overhead on process execution is about one load, one test, one branch (at a guess).

Overhead?

Posted Jul 31, 2026 1:38 UTC (Fri) by mirabilos (subscriber, #84359) [Link]

Aaaaah, so it’s for dynamically-linked executables only. Makes sense.