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authorLinus Torvalds <torvalds@linux-foundation.org>2014-01-22 20:17:48 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-01-22 20:17:48 -0800
commitfe41c2c018b8af9b370a40845f547e22894ff68a (patch)
tree3573a10912e24ffcd48177785043e0de17b8e9d0 /Documentation
parent194e57fd1835564735fd0ba5e3870230861cacd2 (diff)
parent5066a4df1f427faac8372d20494483bb09a4a1cd (diff)
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Merge tag 'dm-3.14-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device-mapper changes from Mike Snitzer: "A lot of attention was paid to improving the thin-provisioning target's handling of metadata operation failures and running out of space. A new 'error_if_no_space' feature was added to allow users to error IOs rather than queue them when either the data or metadata space is exhausted. Additional fixes/features include: - a few fixes to properly support thin metadata device resizing - a solution for reliably waiting for a DM device's embedded kobject to be released before destroying the device - old dm-snapshot is updated to use the dm-bufio interface to take advantage of readahead capabilities that improve snapshot activation - new dm-cache target tunables to control how quickly data is promoted to the cache (fast) device - improved write efficiency of cluster mirror target by combining userspace flush and mark requests" * tag 'dm-3.14-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (35 commits) dm log userspace: allow mark requests to piggyback on flush requests dm space map metadata: fix bug in resizing of thin metadata dm cache: add policy name to status output dm thin: fix pool feature parsing dm sysfs: fix a module unload race dm snapshot: use dm-bufio prefetch dm snapshot: use dm-bufio dm snapshot: prepare for switch to using dm-bufio dm snapshot: use GFP_KERNEL when initializing exceptions dm cache: add block sizes and total cache blocks to status output dm btree: add dm_btree_find_lowest_key dm space map metadata: fix extending the space map dm space map common: make sure new space is used during extend dm: wait until embedded kobject is released before destroying a device dm: remove pointless kobject comparison in dm_get_from_kobject dm snapshot: call destroy_work_on_stack() to pair with INIT_WORK_ONSTACK() dm cache policy mq: introduce three promotion threshold tunables dm cache policy mq: use list_del_init instead of list_del + INIT_LIST_HEAD dm thin: fix set_pool_mode exposed pool operation races dm thin: eliminate the no_free_space flag ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/device-mapper/cache-policies.txt16
-rw-r--r--Documentation/device-mapper/cache.txt51
-rw-r--r--Documentation/device-mapper/thin-provisioning.txt7
3 files changed, 50 insertions, 24 deletions
diff --git a/Documentation/device-mapper/cache-policies.txt b/Documentation/device-mapper/cache-policies.txt
index df52a84..66c2774 100644
--- a/Documentation/device-mapper/cache-policies.txt
+++ b/Documentation/device-mapper/cache-policies.txt
@@ -40,8 +40,11 @@ on hit count on entry. The policy aims to take different cache miss
costs into account and to adjust to varying load patterns automatically.
Message and constructor argument pairs are:
- 'sequential_threshold <#nr_sequential_ios>' and
- 'random_threshold <#nr_random_ios>'.
+ 'sequential_threshold <#nr_sequential_ios>'
+ 'random_threshold <#nr_random_ios>'
+ 'read_promote_adjustment <value>'
+ 'write_promote_adjustment <value>'
+ 'discard_promote_adjustment <value>'
The sequential threshold indicates the number of contiguous I/Os
required before a stream is treated as sequential. The random threshold
@@ -55,6 +58,15 @@ since spindles tend to have good bandwidth. The io_tracker counts
contiguous I/Os to try to spot when the io is in one of these sequential
modes.
+Internally the mq policy maintains a promotion threshold variable. If
+the hit count of a block not in the cache goes above this threshold it
+gets promoted to the cache. The read, write and discard promote adjustment
+tunables allow you to tweak the promotion threshold by adding a small
+value based on the io type. They default to 4, 8 and 1 respectively.
+If you're trying to quickly warm a new cache device you may wish to
+reduce these to encourage promotion. Remember to switch them back to
+their defaults after the cache fills though.
+
cleaner
-------
diff --git a/Documentation/device-mapper/cache.txt b/Documentation/device-mapper/cache.txt
index 719320b..e6b72d3 100644
--- a/Documentation/device-mapper/cache.txt
+++ b/Documentation/device-mapper/cache.txt
@@ -217,36 +217,43 @@ the characteristics of a specific policy, always request it by name.
Status
------
-<#used metadata blocks>/<#total metadata blocks> <#read hits> <#read misses>
-<#write hits> <#write misses> <#demotions> <#promotions> <#blocks in cache>
-<#dirty> <#features> <features>* <#core args> <core args>* <#policy args>
-<policy args>*
-
-#used metadata blocks : Number of metadata blocks used
-#total metadata blocks : Total number of metadata blocks
-#read hits : Number of times a READ bio has been mapped
+<metadata block size> <#used metadata blocks>/<#total metadata blocks>
+<cache block size> <#used cache blocks>/<#total cache blocks>
+<#read hits> <#read misses> <#write hits> <#write misses>
+<#demotions> <#promotions> <#dirty> <#features> <features>*
+<#core args> <core args>* <policy name> <#policy args> <policy args>*
+
+metadata block size : Fixed block size for each metadata block in
+ sectors
+#used metadata blocks : Number of metadata blocks used
+#total metadata blocks : Total number of metadata blocks
+cache block size : Configurable block size for the cache device
+ in sectors
+#used cache blocks : Number of blocks resident in the cache
+#total cache blocks : Total number of cache blocks
+#read hits : Number of times a READ bio has been mapped
to the cache
-#read misses : Number of times a READ bio has been mapped
+#read misses : Number of times a READ bio has been mapped
to the origin
-#write hits : Number of times a WRITE bio has been mapped
+#write hits : Number of times a WRITE bio has been mapped
to the cache
-#write misses : Number of times a WRITE bio has been
+#write misses : Number of times a WRITE bio has been
mapped to the origin
-#demotions : Number of times a block has been removed
+#demotions : Number of times a block has been removed
from the cache
-#promotions : Number of times a block has been moved to
+#promotions : Number of times a block has been moved to
the cache
-#blocks in cache : Number of blocks resident in the cache
-#dirty : Number of blocks in the cache that differ
+#dirty : Number of blocks in the cache that differ
from the origin
-#feature args : Number of feature args to follow
-feature args : 'writethrough' (optional)
-#core args : Number of core arguments (must be even)
-core args : Key/value pairs for tuning the core
+#feature args : Number of feature args to follow
+feature args : 'writethrough' (optional)
+#core args : Number of core arguments (must be even)
+core args : Key/value pairs for tuning the core
e.g. migration_threshold
-#policy args : Number of policy arguments to follow (must be even)
-policy args : Key/value pairs
- e.g. 'sequential_threshold 1024
+policy name : Name of the policy
+#policy args : Number of policy arguments to follow (must be even)
+policy args : Key/value pairs
+ e.g. sequential_threshold
Messages
--------
diff --git a/Documentation/device-mapper/thin-provisioning.txt b/Documentation/device-mapper/thin-provisioning.txt
index 50c44cf..8a7a3d4 100644
--- a/Documentation/device-mapper/thin-provisioning.txt
+++ b/Documentation/device-mapper/thin-provisioning.txt
@@ -235,6 +235,8 @@ i) Constructor
read_only: Don't allow any changes to be made to the pool
metadata.
+ error_if_no_space: Error IOs, instead of queueing, if no space.
+
Data block size must be between 64KB (128 sectors) and 1GB
(2097152 sectors) inclusive.
@@ -276,6 +278,11 @@ ii) Status
contain the string 'Fail'. The userspace recovery tools
should then be used.
+ error_if_no_space|queue_if_no_space
+ If the pool runs out of data or metadata space, the pool will
+ either queue or error the IO destined to the data device. The
+ default is to queue the IO until more space is added.
+
iii) Messages
create_thin <dev id>
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