NPTL_KERN_VER

In Gentoo, this variable can be used to specify the lowest kernel version we want glibc to support. For example, I am completely certain I will never use a kernel older than 2.6.30 on my Gentoo box, so I may want to add NPTL_KERN_VER="2.6.30" to /etc/make.conf. This way, glibc will assume the kernel supports all features that 2.6.30 supports and remove fallback codes written for old kernels.

The default value for NPTL_KERN_VER has been 2.6.9 for years.

That will not make a real difference, though. By switching from 2.6.9 to 2.6.30, the size of my /lib/libc.so.6 reduced by approximately 20KiB, or 1.3%.

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Tags: Gentoo