Document ZFS module parameters.

This is a first draft of a zfs-module-parameters(5) man page. I have
just extracted the parameter name and its description with modinfo,
then checked the source what type it is and its default value.

This will need more work, preferably someone that actually know these
values and what to use them for.

Signed-off-by: Brian Behlendorf <[email protected]>
Closes #1856

1 files changed, 1004 insertions, 0 deletions

diff --git a/man/man5/zfs-module-parameters.5 b/man/man5/zfs-module-parameters.5
new file mode 100644
index 000000000..a54e31f8b
--- /dev/null
+++ b/man/man5/zfs-module-parameters.5
@@ -0,0 +1,1004 @@
+'\" te
+.\" Copyright (c) 2013 by Turbo Fredriksson <[email protected]>. All rights reserved.
+.\" The contents of this file are subject to the terms of the Common Development
+.\" and Distribution License (the "License").  You may not use this file except
+.\" in compliance with the License. You can obtain a copy of the license at
+.\" usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.
+.\"
+.\" See the License for the specific language governing permissions and
+.\" limitations under the License. When distributing Covered Code, include this
+.\" CDDL HEADER in each file and include the License file at
+.\" usr/src/OPENSOLARIS.LICENSE.  If applicable, add the following below this
+.\" CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your
+.\" own identifying information:
+.\" Portions Copyright [yyyy] [name of copyright owner]
+.TH ZFS-MODULE-PARAMETERS 5 "Nov 16, 2013"
+.SH NAME
+zfs\-module\-parameters \- ZFS module parameters
+.SH DESCRIPTION
+.sp
+.LP
+Description of the different parameters to the ZFS module.
+
+.SS "Module parameters"
+.sp
+.LP
+
+.sp
+.ne 2
+.na
+\fBl2arc_feed_again\fR (int)
+.ad
+.RS 12n
+Turbo L2ARC warmup
+.sp
+Use \fB1\fR for yes (default) and \fB0\fR to disable.
+.RE
+
+.sp
+.ne 2
+.na
+\fBl2arc_feed_min_ms\fR (ulong)
+.ad
+.RS 12n
+Min feed interval in milliseconds
+.sp
+Default value: \fB200\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBl2arc_feed_secs\fR (ulong)
+.ad
+.RS 12n
+Seconds between L2ARC writing
+.sp
+Default value: \fB1\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBl2arc_headroom\fR (ulong)
+.ad
+.RS 12n
+Number of max device writes to precache
+.sp
+Default value: \fB2\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBl2arc_headroom_boost\fR (ulong)
+.ad
+.RS 12n
+Compressed l2arc_headroom multiplier
+.sp
+Default value: \fB200\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBl2arc_nocompress\fR (int)
+.ad
+.RS 12n
+Skip compressing L2ARC buffers
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBl2arc_noprefetch\fR (int)
+.ad
+.RS 12n
+Skip caching prefetched buffers
+.sp
+Use \fB1\fR for yes (default) and \fB0\fR to disable.
+.RE
+
+.sp
+.ne 2
+.na
+\fBl2arc_norw\fR (int)
+.ad
+.RS 12n
+No reads during writes
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBl2arc_write_boost\fR (ulong)
+.ad
+.RS 12n
+Extra write bytes during device warmup
+.sp
+Default value: \fB8,388,608\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBl2arc_write_max\fR (ulong)
+.ad
+.RS 12n
+Max write bytes per interval
+.sp
+Default value: \fB8,388,608\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBmetaslab_debug\fR (int)
+.ad
+.RS 12n
+Keep space maps in core to verify frees
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBspa_config_path\fR (charp)
+.ad
+.RS 12n
+SPA config file
+.sp
+Default value: \fB/etc/zfs/zpool.cache\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfetch_array_rd_sz\fR (ulong)
+.ad
+.RS 12n
+Number of bytes in a array_read
+.sp
+Default value: \fB1,048,576\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfetch_block_cap\fR (uint)
+.ad
+.RS 12n
+Max number of blocks to fetch at a time
+.sp
+Default value: \fB256\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfetch_max_streams\fR (uint)
+.ad
+.RS 12n
+Max number of streams per zfetch
+.sp
+Default value: \fB8\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfetch_min_sec_reap\fR (uint)
+.ad
+.RS 12n
+Min time before stream reclaim
+.sp
+Default value: \fB2\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_arc_grow_retry\fR (int)
+.ad
+.RS 12n
+Seconds before growing arc size
+.sp
+Default value: \fB5\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_arc_max\fR (ulong)
+.ad
+.RS 12n
+Max arc size
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_arc_memory_throttle_disable\fR (int)
+.ad
+.RS 12n
+Disable memory throttle
+.sp
+Use \fB1\fR for yes (default) and \fB0\fR to disable.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_arc_meta_limit\fR (ulong)
+.ad
+.RS 12n
+Meta limit for arc size
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_arc_meta_prune\fR (int)
+.ad
+.RS 12n
+Bytes of meta data to prune
+.sp
+Default value: \fB1,048,576\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_arc_min\fR (ulong)
+.ad
+.RS 12n
+Min arc size
+.sp
+Default value: \fB100\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_arc_min_prefetch_lifespan\fR (int)
+.ad
+.RS 12n
+Min life of prefetch block
+.sp
+Default value: \fB100\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_arc_p_min_shift\fR (int)
+.ad
+.RS 12n
+arc_c shift to calc min/max arc_p
+.sp
+Default value: \fB4\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_arc_shrink_shift\fR (int)
+.ad
+.RS 12n
+log2(fraction of arc to reclaim)
+.sp
+Default value: \fB5\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_autoimport_disable\fR (int)
+.ad
+.RS 12n
+Disable pool import at module load
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_dbuf_state_index\fR (int)
+.ad
+.RS 12n
+Calculate arc header index
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_deadman_enabled\fR (int)
+.ad
+.RS 12n
+Enable deadman timer
+.sp
+Use \fB1\fR for yes (default) and \fB0\fR to disable.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_deadman_synctime\fR (ulong)
+.ad
+.RS 12n
+Expire in units of zfs_txg_synctime_ms
+.sp
+Default value: \fB1,000\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_dedup_prefetch\fR (int)
+.ad
+.RS 12n
+Enable prefetching dedup-ed blks
+.sp
+Use \fB1\fR for yes (default) and \fB0\fR to disable.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_disable_dup_eviction\fR (int)
+.ad
+.RS 12n
+Disable duplicate buffer eviction
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_expire_snapshot\fR (int)
+.ad
+.RS 12n
+Seconds to expire .zfs/snapshot
+.sp
+Default value: \fB300\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_flags\fR (int)
+.ad
+.RS 12n
+Set additional debugging flags
+.sp
+Default value: \fB1\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_free_min_time_ms\fR (int)
+.ad
+.RS 12n
+Min millisecs to free per txg
+.sp
+Default value: \fB1,000\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_immediate_write_sz\fR (long)
+.ad
+.RS 12n
+Largest data block to write to zil
+.sp
+Default value: \fB32,768\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_mdcomp_disable\fR (int)
+.ad
+.RS 12n
+Disable meta data compression
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_no_scrub_io\fR (int)
+.ad
+.RS 12n
+Set for no scrub I/O
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_no_scrub_prefetch\fR (int)
+.ad
+.RS 12n
+Set for no scrub prefetching
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_no_write_throttle\fR (int)
+.ad
+.RS 12n
+Disable write throttling
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_nocacheflush\fR (int)
+.ad
+.RS 12n
+Disable cache flushes
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_nopwrite_enabled\fR (int)
+.ad
+.RS 12n
+Enable NOP writes
+.sp
+Use \fB1\fR for yes (default) and \fB0\fR to disable.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_pd_blks_max\fR (int)
+.ad
+.RS 12n
+Max number of blocks to prefetch
+.sp
+Default value: \fB100\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_prefetch_disable\fR (int)
+.ad
+.RS 12n
+Disable all ZFS prefetching
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_read_chunk_size\fR (long)
+.ad
+.RS 12n
+Bytes to read per chunk
+.sp
+Default value: \fB1,048,576\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_read_history\fR (int)
+.ad
+.RS 12n
+Historic statistics for the last N reads
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_read_history_hits\fR (int)
+.ad
+.RS 12n
+Include cache hits in read history
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_recover\fR (int)
+.ad
+.RS 12n
+Set to attempt to recover from fatal errors. This should only be used as a
+last resort, as it typically results in leaked space, or worse.
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_resilver_delay\fR (int)
+.ad
+.RS 12n
+Number of ticks to delay resilver
+.sp
+Default value: \fB2\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_resilver_min_time_ms\fR (int)
+.ad
+.RS 12n
+Min millisecs to resilver per txg
+.sp
+Default value: \fB3,000\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_scan_idle\fR (int)
+.ad
+.RS 12n
+Idle window in clock ticks
+.sp
+Default value: \fB50\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_scan_min_time_ms\fR (int)
+.ad
+.RS 12n
+Min millisecs to scrub per txg
+.sp
+Default value: \fB1,000\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_scrub_delay\fR (int)
+.ad
+.RS 12n
+Number of ticks to delay scrub
+.sp
+Default value: \fB4\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_sync_pass_deferred_free\fR (int)
+.ad
+.RS 12n
+Defer frees starting in this pass
+.sp
+Default value: \fB2\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_sync_pass_dont_compress\fR (int)
+.ad
+.RS 12n
+Don't compress starting in this pass
+.sp
+Default value: \fB5\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_sync_pass_rewrite\fR (int)
+.ad
+.RS 12n
+Rewrite new bps starting in this pass
+.sp
+Default value: \fB2\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_top_maxinflight\fR (int)
+.ad
+.RS 12n
+Max I/Os per top-level
+.sp
+Default value: \fB32\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_txg_history\fR (int)
+.ad
+.RS 12n
+Historic statistics for the last N txgs
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_txg_synctime_ms\fR (int)
+.ad
+.RS 12n
+Target milliseconds between txg sync
+.sp
+Default value: \fB1,000\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_txg_timeout\fR (int)
+.ad
+.RS 12n
+Max seconds worth of delta per txg
+.sp
+Default value: \fB5\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_vdev_aggregation_limit\fR (int)
+.ad
+.RS 12n
+Max vdev I/O aggregation size
+.sp
+Default value: \fB131,072\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_vdev_cache_bshift\fR (int)
+.ad
+.RS 12n
+Shift size to inflate reads too
+.sp
+Default value: \fB16\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_vdev_cache_max\fR (int)
+.ad
+.RS 12n
+Inflate reads small than max
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_vdev_cache_size\fR (int)
+.ad
+.RS 12n
+Total size of the per-disk cache
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_vdev_max_pending\fR (int)
+.ad
+.RS 12n
+Max pending per-vdev I/Os
+.sp
+Default value: \fB10\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_vdev_min_pending\fR (int)
+.ad
+.RS 12n
+Min pending per-vdev I/Os
+.sp
+Default value: \fB4\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_vdev_mirror_switch_us\fR (int)
+.ad
+.RS 12n
+Switch mirrors every N usecs
+.sp
+Default value: \fB10,000\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_vdev_ramp_rate\fR (int)
+.ad
+.RS 12n
+Exponential I/O issue ramp-up rate
+.sp
+Default value: \fB2\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_vdev_read_gap_limit\fR (int)
+.ad
+.RS 12n
+Aggregate read I/O over gap
+.sp
+Default value: \fB32,768\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_vdev_scheduler\fR (charp)
+.ad
+.RS 12n
+I/O scheduler
+.sp
+Default value: \fBnoop\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_vdev_time_shift\fR (int)
+.ad
+.RS 12n
+Deadline time shift for vdev I/O
+.sp
+Default value: \fB29\fR (each bucket is 0.537 seconds).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_vdev_write_gap_limit\fR (int)
+.ad
+.RS 12n
+Aggregate write I/O over gap
+.sp
+Default value: \fB4,096\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_write_limit_inflated\fR (ulong)
+.ad
+.RS 12n
+Inflated txg write limit
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_write_limit_max\fR (ulong)
+.ad
+.RS 12n
+Max txg write limit
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_write_limit_min\fR (ulong)
+.ad
+.RS 12n
+Min txg write limit
+.sp
+Default value: \fB33,554,432\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_write_limit_override\fR (ulong)
+.ad
+.RS 12n
+Override txg write limit
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_write_limit_shift\fR (int)
+.ad
+.RS 12n
+log2(fraction of memory) per txg
+.sp
+Default value: \fB3\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_zevent_cols\fR (int)
+.ad
+.RS 12n
+Max event column width
+.sp
+Default value: \fB80\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_zevent_console\fR (int)
+.ad
+.RS 12n
+Log events to the console
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_zevent_len_max\fR (int)
+.ad
+.RS 12n
+Max event queue length
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzil_replay_disable\fR (int)
+.ad
+.RS 12n
+Disable intent logging replay
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzil_slog_limit\fR (ulong)
+.ad
+.RS 12n
+Max commit bytes to separate log device
+.sp
+Default value: \fB1,048,576\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzio_bulk_flags\fR (int)
+.ad
+.RS 12n
+Additional flags to pass to bulk buffers
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzio_delay_max\fR (int)
+.ad
+.RS 12n
+Max zio millisec delay before posting event
+.sp
+Default value: \fB30,000\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzio_injection_enabled\fR (int)
+.ad
+.RS 12n
+Enable fault injection
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzio_requeue_io_start_cut_in_line\fR (int)
+.ad
+.RS 12n
+Prioritize requeued I/O
+.sp
+Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzvol_inhibit_dev\fR (uint)
+.ad
+.RS 12n
+Do not create zvol device nodes
+.sp
+Use \fB1\fR for yes and \fB0\fR for no (default).
+.RE
+
+.sp
+.ne 2
+.na
+\fBzvol_major\fR (uint)
+.ad
+.RS 12n
+Major number for zvol device
+.sp
+Default value: \fB230\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzvol_max_discard_blocks\fR (ulong)
+.ad
+.RS 12n
+Max number of blocks to discard at once
+.sp
+Default value: \fB16,384\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzvol_threads\fR (uint)
+.ad
+.RS 12n
+Number of threads for zvol device
+.sp
+Default value: \fB32\fR.
+.RE
+