[drewg123]

Is ARC really non-reclaimable on Linux?

At least on FreeBSD, there is a kmem_cache_reap() that is called from the core kernel VM system's low memory handlers.

Looking at the linux code in openzfs, it looks like there is an "spl_kmem_cache_reap_now()" function. Maybe the problem is the kernel dev's anti-ZFS stance, and it can't be hooked into the right place (eg, the kernel's VM low memory handling code)?

[MrDrMcCoy]

It's reclaimable, but opaque. The ARC just looks like used RAM rather than file cache, which throws off various means of accounting.

[nubinetwork]

echo 3 > /proc/sys/vm/drop_caches

(Bear in mind that 3 is the most aggressive but other than exporting the pool, it's the only way to dump the cache, especially if you boot off ZFS)