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Update OpenZFS module parameters (#76)

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- Renamed the page to "Module Parameter" since it now applies
  equally to Linux and FreeBSD.

- Updated spl_kmem_cache_expire, spl_kmem_cache_obj_per_slab_min,
  spl_kmem_cache_kmem_limit to note the last version they were
  included in.

- Added new l2arc_mfuonly, l2arc_rebuild_blocks_min_l2size,
  l2arc_rebuild_enabled, and l2arc_trim_ahead options which
  were added in OpenZFS 2.0 for the persistent L2ARC feature.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This commit is contained in:
Brian Behlendorf
2020-11-25 09:42:02 -08:00
committed by GitHub
parent 40e194d6fc
commit f7ee059f28
1 changed files with 134 additions and 5 deletions
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139
docs/Performance and Tuning/ZFS on Linux Module Parameters.rst → docs/Performance and Tuning/Module Parameters.rst
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@@ -1,5 +1,5 @@
ZFS on Linux Module Parameters
==============================
Module Parameters
=================
Most of the ZFS kernel module parameters are accessible in the SysFS
``/sys/module/zfs/parameters`` directory. Current value can be observed
@@ -140,9 +140,13 @@ ARC
- `l2arc_headroom <#l2arc-headroom>`__
- `l2arc_headroom_boost <#l2arc-headroom-boost>`__
- `l2arc_meta_percent <#l2arc-meta-percent>`__
- `l2arc_mfuonly <#l2arc-mfuonly>`__
- `l2arc_nocompress <#l2arc-nocompress>`__
- `l2arc_noprefetch <#l2arc-noprefetch>`__
- `l2arc_norw <#l2arc-norw>`__
- `l2arc_rebuild_blocks_min_l2size <#l2arc-rebuild-blocks-min-l2size>`__
- `l2arc_rebuild_enabled <#l2arc-rebuild-enabled>`__
- `l2arc_trim_ahead <#l2arc-trim-ahead>`__
- `l2arc_write_boost <#l2arc-write-boost>`__
- `l2arc_write_max <#l2arc-write-max>`__
- `zfs_multilist_num_sublists <#zfs-multilist-num-sublists>`__
@@ -335,9 +339,13 @@ L2ARC
- `l2arc_headroom <#l2arc-headroom>`__
- `l2arc_headroom_boost <#l2arc-headroom-boost>`__
- `l2arc_meta_percent <#l2arc-meta-percent>`__
- `l2arc_mfuonly <#l2arc-mfuonly>`__
- `l2arc_nocompress <#l2arc-nocompress>`__
- `l2arc_noprefetch <#l2arc-noprefetch>`__
- `l2arc_norw <#l2arc-norw>`__
- `l2arc_rebuild_blocks_min_l2size <#l2arc-rebuild-blocks-min-l2size>`__
- `l2arc_rebuild_enabled <#l2arc-rebuild-enabled>`__
- `l2arc_trim_ahead <#l2arc-trim-ahead>`__
- `l2arc_write_boost <#l2arc-write-boost>`__
- `l2arc_write_max <#l2arc-write-max>`__
@@ -820,9 +828,13 @@ Index
- `l2arc_headroom <#l2arc-headroom>`__
- `l2arc_headroom_boost <#l2arc-headroom-boost>`__
- `l2arc_meta_percent <#l2arc-meta-percent>`__
- `l2arc_mfuonly <#l2arc-mfuonly>`__
- `l2arc_nocompress <#l2arc-nocompress>`__
- `l2arc_noprefetch <#l2arc-noprefetch>`__
- `l2arc_norw <#l2arc-norw>`__
- `l2arc_rebuild_blocks_min_l2size <#l2arc-rebuild-blocks-min-l2size>`__
- `l2arc_rebuild_enabled <#l2arc-rebuild-enabled>`__
- `l2arc_trim_ahead <#l2arc-trim-ahead>`__
- `l2arc_write_boost <#l2arc-write-boost>`__
- `l2arc_write_max <#l2arc-write-max>`__
- `zfs_lua_max_instrlimit <#zfs-lua-max-instrlimit>`__
@@ -1239,6 +1251,34 @@ This parameter limits L2ARC writes and rebuild to achieve it.
| Versions Affected | v2.0 and later |
+-------------------+-------------------------------------------------+
l2arc_mfuonly
~~~~~~~~~~~~~
Controls whether only MFU metadata and data are cached from ARC into L2ARC.
This may be desirable to avoid wasting space on L2ARC when reading/writing
large amounts of data that are not expected to be accessed more than once.
By default both MRU and MFU data and metadata are cached in the L2ARC.
+-------------------+-------------------------------------------------+
| l2arc_mfuonly | Notes |
+===================+=================================================+
| Tags | `ARC <#arc>`__, `L2ARC <#l2arc>`__ |
+-------------------+-------------------------------------------------+
| When to change | When accessing a large amount of data only |
| | once. |
+-------------------+-------------------------------------------------+
| Data Type | boolean |
+-------------------+-------------------------------------------------+
| Range | 0=store MRU and MFU blocks in cache device, |
| | 1=store MFU blocks in cache device |
+-------------------+-------------------------------------------------+
| Default | 0 |
+-------------------+-------------------------------------------------+
| Change | Dynamic |
+-------------------+-------------------------------------------------+
| Versions Affected | v2.0 and later |
+-------------------+-------------------------------------------------+
l2arc_noprefetch
~~~~~~~~~~~~~~~~
@@ -1297,6 +1337,95 @@ Disables writing to cache devices while they are being read.
| Versions Affected | all |
+-------------------+-------------------------------------------------+
l2arc_rebuild_blocks_min_l2size
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The minimum required size (in bytes) of an L2ARC device in order to
write log blocks in it. The log blocks are used upon importing the pool
to rebuild the persistent L2ARC. For L2ARC devices less than 1GB the
overhead involved offsets most of benefit so log blocks are not written
for cache devices smaller than this.
+---------------------------------+-----------------------------------+
| l2arc_rebuild_blocks_min_l2size | Notes |
+=================================+===================================+
| Tags | `ARC <#arc>`__, |
| | `L2ARC <#l2arc>`__ |
+---------------------------------+-----------------------------------+
| When to change | The cache device is small and |
| | the pool is frequently imported. |
+---------------------------------+-----------------------------------+
| Data Type | bytes |
+---------------------------------+-----------------------------------+
| Range | 0 to UINT64_MAX |
+---------------------------------+-----------------------------------+
| Default | 1,073,741,824 |
+---------------------------------+-----------------------------------+
| Change | Dynamic |
+---------------------------------+-----------------------------------+
| Versions Affected | v2.0 and later |
+---------------------------------+-----------------------------------+
l2arc_rebuild_enabled
~~~~~~~~~~~~~~~~~~~~~
Rebuild the persistent L2ARC when importing a pool.
+-----------------------+---------------------------------------------+
| l2arc_rebuild_enabled | Notes |
+=======================+=============================================+
| Tags | `ARC <#arc>`__, `L2ARC <#l2arc>`__ |
+-----------------------+---------------------------------------------+
| When to change | If there are problems importing a pool or |
| | attaching an L2ARC device. |
+-----------------------+---------------------------------------------+
| Data Type | boolean |
+-----------------------+---------------------------------------------+
| Range | 0=disable persistent L2ARC rebuild, |
| | 1=enable persistent L2ARC rebuild |
+-----------------------+---------------------------------------------+
| Default | 1 |
+-----------------------+---------------------------------------------+
| Change | Dynamic |
+-----------------------+---------------------------------------------+
| Versions Affected | v2.0 and later |
+-----------------------+---------------------------------------------+
l2arc_trim_ahead
~~~~~~~~~~~~~~~~
Once the cache device has been filled TRIM ahead of the current write size
``l2arc_write_max`` on L2ARC devices by this percentage. This can speed
up future writes depending on the performance characteristics of the
cache device.
When set to 100% TRIM twice the space required to accommodate upcoming
writes. A minimum of 64MB will be trimmed. If set it enables TRIM of
the whole L2ARC device when it is added to a pool. By default, this
option is disabled since it can put significant stress on the underlying
storage devices.
+-------------------+-------------------------------------------------+
| l2arc_trim_ahead | Notes |
+===================+=================================================+
| Tags | `ARC <#arc>`__, `L2ARC <#l2arc>`__ |
+-------------------+-------------------------------------------------+
| When to change | Consider setting for cache devices which |
| | effeciently handle TRIM commands. |
+-------------------+-------------------------------------------------+
| Data Type | ulong |
+-------------------+-------------------------------------------------+
| Units | percent of l2arc_write_max |
+-------------------+-------------------------------------------------+
| Range | 0 to 100 |
+-------------------+-------------------------------------------------+
| Default | 0 |
+-------------------+-------------------------------------------------+
| Change | Dynamic |
+-------------------+-------------------------------------------------+
| Versions Affected | v2.0 and later |
+-------------------+-------------------------------------------------+
l2arc_write_boost
~~~~~~~~~~~~~~~~~
@@ -8925,7 +9054,7 @@ Data Type bitmask
Range 0x01 - Aging (illumos), 0x02 - Low memory (Linux)
Default 0x02
Change Dynamic
Versions Affected v0.6.1
Versions Affected v0.6.1 to v0.8.x
===================== =================================================
spl_kmem_cache_kmem_limit
@@ -8966,7 +9095,7 @@ Units pages
Range TBD
Default PAGE_SIZE / 4
Change Dynamic
Versions Affected v0.7.0
Versions Affected v0.7.0 to v0.8.x
========================= ====================
spl_kmem_cache_max_size
@@ -9012,7 +9141,7 @@ Units kmem cache objects
Range TBD
Default 8
Change Dynamic
Versions Affected v0.7.0
Versions Affected v0.7.0 to v0.8.x
=========================== ====================
spl_kmem_cache_obj_per_slab_min