add option to link sbin/kresd to jemalloc

And by default do so iff jemalloc is found.

I chose the simplicity of adding the chosen allocator just in the single binary. Other sbin/* don't matter really, and dynamic libs (e.g. modules) will just follow whoever loaded them.

added performance label

added 8 commits

• 752a1f82...bad88c16 - 4 commits from branch master
• b6ad9e23 - add option to link sbin/kresd to jemalloc
• 844488bf - distro/pkg/*: build with jemalloc
• 016f491b - use jemalloc in CI
• 0cf3dac7 - NEWS, doc: document jemalloc

Compare with previous version

Testing

TL;DR: I re-tested memory consumption of kresd 5.5.3 with four different allocators: glibc, jemalloc, tcmalloc, musl libc. There glibc and tcmalloc turned out surprisingly bad.

One issue is that in periods with less traffic they don't return memory to OS and remain close the maximum. But even the maximums get way worse over time (compared to jemalloc and musl libc). The effect is mainly visible when the query traffic repeatedly spikes close to amount that kresd can handle (or over it).

It was fairly easy to make glibc and tcmalloc peak 100 MB higher in memory usage than jemalloc and musl with the same traffic. That was within several minutes, for a single kresd process, and it seemed like further traffic spikes could keep pushing the memory peaks higher. With jemalloc and musl the peaks seemed similar every time.

Common testing setup:

• Default settings (e.g. no forwarding), querying over UDP.
• No real memory leaks happened, so differences are due to overheads of the allocators, probably mainly due to internal fragmentation.
• Queries from https://github.com/DNS-OARC/sample-query-data
• Just simple resperf as generator of client traffic.
• All variants running in parallel, for easier comparison of behavior.

added 14 commits

• 0cf3dac7...4a44fe52 - 10 commits from branch master
• 4da7df65 - add option to link sbin/kresd to jemalloc
• d409727e - distro/pkg/*: build with jemalloc
• 5a02d581 - use jemalloc in CI
• f7c47a2c - NEWS, doc: document jemalloc

Compare with previous version

merged

mentioned in commit 74048dc5