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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.

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 3y ago
It's reclaimable, but opaque. The ARC just looks like used RAM rather than file cache, which throws off various means of accounting.
nubinetwork 3y ago
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)