zfsonlinux/zfs — pull request #2555 by dweeezil (2014-07-30 12:36:29+00:00)
Title: Illumos 4897

Illumos 4897 - Space accounting mismatch in L2ARC/zpool

Reviewed by: Matthew Ahrens
Reviewed by: Boris Protopopov
Approved by: Dan McDonald

From the illumos issue tracker:

L2ARC vdev space usage statistics are calculated as the delta
between the maximum and minimum vdev offset ever written to
by the L2ARC fill thread, but do not inform the user of how
much space in between these two offsets is actually taken up by
cached buffers. This fix changes that so that vdev space usage
stats on L2ARC devices accurately track the volume of buffers
stored on them, allowing users to see the exact L2ARC usage in
"zpool iostat -v".

References:
https://www.illumos.org/issues/4897
Ported by: Tim Chase