gc: don't re-open cache so often

Re-opening the cache every interval (1s by default) causes fsync. Normally that isn't noticeable, but on encrypted ZFS it causes high CPU consumption (even when "idle"). Reported on gitter.

added performance label

added 30 commits

• e3946fd3...4925fda0 - 27 commits from branch master
• 415f564e - gc: don't re-open cache so often
• f991063a - gc: make state in kr_cache_gc() explicit
• f13e4cfb - gc: make the log more readable

Compare with previous version

unmarked as a Work In Progress

I reviewed this, cleaned up and did some testing.

@amrazek: if I look correctly, there should be only trivial conflicts with the sysrepo-related changes. I see no need to resolve them quickly. Note that some events (e.g. changing location of cache) will newly need the GC to explicitly call kr_cache_gc_free_state(&gc_state); to trigger re-opening the cache.

I didn't check the code changes yet, but it seems to work as expected. This is such a quality of life change for my HDD LED it makes me want to release 5.0.2 :)

merged

mentioned in commit 3b747b57

mentioned in issue #549 (closed)

mentioned in issue #563 (closed)