Improving ZFS performance for large directories

[Artem Belevich]

On Wed, Jan 30, 2013 at 12:59 PM, Kevin Day <toasty at dragondata.com> wrote:
>
> Does anyone here understand the significance of "used" being higher than "limit"? Is the limit only a suggestion, or are there cases where there'a certain metadata that must be in arc, and it's particularly large here?

arc_meta_limit is a soft limit which basically tells ARC to attempt
evicting metadata entries and reuse their buffers as opposed to
allocating new memory and growing ARC. According to the comment next
to arc_evict() function, it's a best-effort attempt and eviction is
not guaranteed. That could potentially allow meta_size to remain above
meta_limit.

--Artem