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085321621e
Currently the ARC state (MFU/MRU) of cached L2ARC buffer and their
content type is unknown. Knowing this information may prove beneficial
in adjusting the L2ARC caching policy.
This commit adds L2ARC arcstats that display the aligned size
(in bytes) of L2ARC buffers according to their content type
(data/metadata) and according to their ARC state (MRU/MFU or
prefetch). It also expands the existing evict_l2_eligible arcstat to
differentiate between MFU and MRU buffers.
L2ARC caches buffers from the MRU and MFU lists of ARC. Upon caching a
buffer, its ARC state (MRU/MFU) is stored in the L2 header
(b_arcs_state). The l2_m{f,r}u_asize arcstats reflect the aligned size
(in bytes) of L2ARC buffers according to their ARC state (based on
b_arcs_state). We also account for the case where an L2ARC and ARC
cached MRU or MRU_ghost buffer transitions to MFU. The l2_prefetch_asize
reflects the alinged size (in bytes) of L2ARC buffers that were cached
while they had the prefetch flag set in ARC. This is dynamically updated
as the prefetch flag of L2ARC buffers changes.
When buffers are evicted from ARC, if they are determined to be L2ARC
eligible then their logical size is recorded in
evict_l2_eligible_m{r,f}u arcstats according to their ARC state upon
eviction.
Persistent L2ARC:
When committing an L2ARC buffer to a log block (L2ARC metadata) its
b_arcs_state and prefetch flag is also stored. If the buffer changes
its arcstate or prefetch flag this is reflected in the above arcstats.
However, the L2ARC metadata cannot currently be updated to reflect this
change.
Example: L2ARC caches an MRU buffer. L2ARC metadata and arcstats count
this as an MRU buffer. The buffer transitions to MFU. The arcstats are
updated to reflect this. Upon pool re-import or on/offlining the L2ARC
device the arcstats are cleared and the buffer will now be counted as an
MRU buffer, as the L2ARC metadata were not updated.
Bug fix:
- If l2arc_noprefetch is set, arc_read_done clears the L2CACHE flag of
an ARC buffer. However, prefetches may be issued in a way that
arc_read_done() is bypassed. Instead, move the related code in
l2arc_write_eligible() to account for those cases too.
Also add a test and update manpages for l2arc_mfuonly module parameter,
and update the manpages and code comments for l2arc_noprefetch.
Move persist_l2arc tests to l2arc.
Reviewed-by: Ryan Moeller <freqlabs@FreeBSD.org>
Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: George Amanakis <gamanakis@gmail.com>
Closes #10743
593 lines
6.2 KiB
Groff
593 lines
6.2 KiB
Groff
.\"
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.\" This file and its contents are supplied under the terms of the
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.\" Common Development and Distribution License ("CDDL"), version 1.0.
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.\" You may only use this file in accordance with the terms of version
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.\" 1.0 of the CDDL.
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.\"
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.\" A full copy of the text of the CDDL should have accompanied this
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.\" source. A copy of the CDDL is also available via the Internet at
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.\" http://www.illumos.org/license/CDDL.
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.\"
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.\"
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.\" Copyright 2014 Adam Stevko. All rights reserved.
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.\" Copyright (c) 2015 by Delphix. All rights reserved.
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.\" Copyright (c) 2020 by AJ Jordan. All rights reserved.
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.\"
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.TH ARCSTAT 1 "Aug 24, 2020" OpenZFS
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.SH NAME
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arcstat \- report ZFS ARC and L2ARC statistics
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.SH SYNOPSIS
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.LP
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.nf
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\fBarcstat\fR [\fB-hvx\fR] [\fB-f field[,field]...\fR] [\fB-o file\fR] [\fB-s string\fR] [\fBinterval\fR [\fBcount\fR]]
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.fi
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.SH DESCRIPTION
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.LP
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The \fBarcstat\fR utility print various ZFS ARC and L2ARC statistics in
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vmstat-like fashion.
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.sp
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.sp
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.LP
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The \fBarcstat\fR command reports the following information:
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.sp
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.ne 2
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.\"
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.sp
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.ne 1
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.na
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\fBc \fR
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.ad
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.RS 14n
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ARC target size
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.RE
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.sp
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.ne 2
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.na
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\fBdh% \fR
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.ad
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.RS 14n
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Demand data hit percentage
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.RE
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.sp
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.ne 2
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.na
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\fBdm% \fR
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.ad
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.RS 14n
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Demand data miss percentage
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.RE
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.sp
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.ne 2
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.na
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\fBmfu \fR
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.ad
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.RS 14n
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MFU list hits per second
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.RE
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.sp
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.ne 2
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.na
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\fBmh% \fR
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.ad
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.RS 14n
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Metadata hit percentage
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.RE
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.sp
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.ne 2
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.na
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\fBmm% \fR
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.ad
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.RS 14n
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Metadata miss percentage
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.RE
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.sp
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.ne 2
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.na
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\fBmru \fR
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.ad
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.RS 14n
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MRU list hits per second
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.RE
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.sp
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.ne 2
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.na
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\fBph% \fR
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.ad
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.RS 14n
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Prefetch hits percentage
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.RE
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.sp
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.ne 2
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.na
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\fBpm% \fR
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.ad
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.RS 14n
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Prefetch miss percentage
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.RE
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.sp
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.ne 2
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.na
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\fBdhit \fR
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.ad
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.RS 14n
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Demand data hits per second
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.RE
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.sp
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.ne 2
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.na
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\fBdmis \fR
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.ad
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.RS 14n
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Demand data misses per second
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.RE
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.sp
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.ne 2
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.na
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\fBhit% \fR
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.ad
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.RS 14n
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ARC hit percentage
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.RE
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.sp
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.ne 2
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.na
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\fBhits \fR
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.ad
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.RS 14n
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ARC reads per second
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.RE
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.sp
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.ne 2
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.na
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\fBmfug \fR
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.ad
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.RS 14n
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MFU ghost list hits per second
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.RE
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.sp
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.ne 2
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.na
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\fBmhit \fR
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.ad
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.RS 14n
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Metadata hits per second
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.RE
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.sp
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.ne 2
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.na
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\fBmiss \fR
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.ad
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.RS 14n
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ARC misses per second
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.RE
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.sp
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.ne 2
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.na
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\fBmmis \fR
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.ad
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.RS 14n
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Metadata misses per second
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.RE
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.sp
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.ne 2
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.na
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\fBmrug \fR
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.ad
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.RS 14n
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MRU ghost list hits per second
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.RE
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.sp
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.ne 2
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.na
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\fBphit \fR
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.ad
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.RS 14n
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Prefetch hits per second
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.RE
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.sp
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.ne 2
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.na
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\fBpmis \fR
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.ad
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.RS 14n
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Prefetch misses per second
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.RE
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.sp
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.ne 2
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.na
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\fBread \fR
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.ad
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.RS 14n
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Total ARC accesses per second
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.RE
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.sp
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.ne 2
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.na
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\fBtime \fR
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.ad
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.RS 14n
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Time
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.RE
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.sp
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.ne 2
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.na
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\fBsize \fR
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.ad
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.RS 14n
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ARC size
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.RE
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.sp
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.ne 2
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.na
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\fBarcsz \fR
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.ad
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.RS 14n
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Alias for \fBsize\fR
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.RE
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.sp
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.ne 2
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.na
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\fBdread \fR
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.ad
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.RS 14n
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Demand data accesses per second
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.RE
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.sp
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.ne 2
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.na
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\fBeskip \fR
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.ad
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.RS 14n
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evict_skip per second
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.RE
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.sp
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.ne 2
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.na
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\fBmiss% \fR
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.ad
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.RS 14n
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ARC miss percentage
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.RE
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.sp
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.ne 2
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.na
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\fBmread \fR
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.ad
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.RS 14n
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Metadata accesses per second
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.RE
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.sp
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.ne 2
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.na
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\fBpread \fR
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.ad
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.RS 14n
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Prefetch accesses per second
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.RE
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.sp
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.ne 2
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.na
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\fBl2hit% \fR
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.ad
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.RS 14n
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L2ARC access hit percentage
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.RE
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.sp
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.ne 2
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.na
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\fBl2hits \fR
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.ad
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.RS 14n
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L2ARC hits per second
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.RE
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.sp
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.ne 2
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.na
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\fBl2miss \fR
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.ad
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.RS 14n
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L2ARC misses per second
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.RE
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.sp
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.ne 2
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.na
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\fBl2read \fR
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.ad
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.RS 14n
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Total L2ARC accesses per second
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.RE
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.sp
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.ne 2
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.na
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\fBl2pref \fR
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.ad
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.RS 14n
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L2ARC prefetch allocated size per second
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.RE
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.sp
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.ne 2
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.na
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\fBl2pref% \fR
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.ad
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.RS 14n
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L2ARC prefetch allocated size percentage
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.RE
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.sp
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.ne 2
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.na
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\fBl2mfu \fR
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.ad
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.RS 14n
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L2ARC MFU allocated size per second
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.RE
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.sp
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.ne 2
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.na
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\fBl2mfu% \fR
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.ad
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.RS 14n
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L2ARC MFU allocated size percentage
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.RE
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.sp
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.ne 2
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.na
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\fBl2mru \fR
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.ad
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.RS 14n
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L2ARC MRU allocated size per second
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.RE
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.sp
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.ne 2
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.na
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\fBl2mru% \fR
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.ad
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.RS 14n
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L2ARC MRU allocated size percentage
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.RE
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.sp
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.ne 2
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.na
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\fBl2data \fR
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.ad
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.RS 14n
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L2ARC data (buf content) allocated size per second
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.RE
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.sp
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.ne 2
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.na
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\fBl2data% \fR
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.ad
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.RS 14n
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L2ARC data (buf content) allocated size percentage
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.RE
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.sp
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.ne 2
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.na
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\fBl2meta \fR
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.ad
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.RS 14n
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L2ARC metadata (buf content) allocated size per second
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.RE
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.sp
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.ne 2
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.na
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\fBl2meta% \fR
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.ad
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.RS 14n
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L2ARC metadata (buf content) allocated size percentage
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.RE
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.sp
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.ne 2
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.na
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\fBl2size \fR
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.ad
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.RS 14n
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Size of the L2ARC
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.RE
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.sp
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.ne 2
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.na
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\fBmtxmis \fR
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.ad
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.RS 14n
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mutex_miss per second
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.RE
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.sp
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.ne 2
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.na
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\fBl2bytes \fR
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.ad
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.RS 14n
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Bytes read per second from the L2ARC
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.RE
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.sp
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.ne 2
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.na
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\fBl2miss% \fR
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.ad
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.RS 14n
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L2ARC access miss percentage
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.RE
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.sp
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.ne 2
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.na
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\fBl2asize \fR
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.ad
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.RS 14n
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Actual (compressed) size of the L2ARC
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.RE
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.sp
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.ne 2
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.na
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\fBgrow \fR
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.ad
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.RS 14n
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ARC grow disabled
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.RE
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.sp
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.ne 2
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.na
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\fBneed \fR
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.ad
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.RS 14n
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ARC reclaim needed
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.RE
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.sp
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.ne 2
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.na
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\fBfree \fR
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.ad
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.RS 14n
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The ARC's idea of how much free memory there is, which includes evictable memory in the page cache.
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Since the ARC tries to keep \fBavail\fR above zero, \fBavail\fR is usually more instructive to observe than \fBfree\fR.
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.RE
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.sp
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.ne 2
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.na
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\fBavail \fR
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.ad
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.RS 14n
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The ARC's idea of how much free memory is available to it, which is a bit less than \fBfree\fR.
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May temporarily be negative, in which case the ARC will reduce the target size \fBc\fR.
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.RE
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.\"
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.SH OPTIONS
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.LP
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The following options are supported:
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.sp
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.ne 2
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.na
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\fB\fB-f\fR\fR
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.ad
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.RS 12n
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Display only specific fields. See \fBDESCRIPTION\fR for supported statistics.
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.RE
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.sp
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.ne 2
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.na
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\fB\fB-h\fR\fR
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.ad
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.RS 12n
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Display help message.
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.RE
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.sp
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.ne 2
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.na
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\fB\fB-o\fR\fR
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.ad
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.RS 12n
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Report statistics to a file instead of the standard output.
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.RE
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.sp
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.ne 2
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.na
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\fB\fB-s\fR\fR
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.ad
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.RS 12n
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Display data with a specified separator (default: 2 spaces).
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.RE
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.sp
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.ne 2
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.na
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\fB\fB-x\fR\fR
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.ad
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.RS 12n
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Print extended stats (same as -f time,mfu,mru,mfug,mrug,eskip,mtxmis,dread,pread,read).
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.RE
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.sp
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.ne 2
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.na
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\fB\fB-v\fR\fR
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.ad
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.RS 12n
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Show field headers and definitions
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.RE
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.SH OPERANDS
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.LP
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The following operands are supported:
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.sp
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.ne 2
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.na
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\fB\fIcount\fR\fR
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.ad
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.RS 12n
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Display only \fIcount\fR reports.
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.RE
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.sp
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.ne 2
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.na
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\fB\fIinterval\fR\fR
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.ad
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.RS 12n
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Specify the sampling interval in seconds.
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.RE
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.SH AUTHORS
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.LP
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arcstat was originally written in Perl by Neelakanth Nadgir and supported only ZFS ARC statistics.
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Mike Harsch updated it to support L2ARC statistics.
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John Hixson ported it to Python for FreeNAS over some beer, after which many individuals from the OpenZFS community continued to maintain and improve it.
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