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dm cache: add block sizes and total cache blocks to status output 

Improve cache_status to emit:
<metadata block size> <#used metadata blocks>/<#total metadata blocks>
<cache block size> <#used cache blocks>/<#total cache blocks>
...

Adding the block sizes allows for easier calculation of the overall size
of both the metadata and cache devices.  Adding <#total cache blocks>
provides useful context for how much of the cache is used.

Unfortunately these additions to the status will require updates to
users' scripts that monitor the cache status.  But these changes help
provide more comprehensive information about the cache device and will
simplify tools that are being developed to manage dm-cache devices --
because they won't need to issue 3 operations to cobble together the
information that we can easily provide via a single status ioctl.

While updating the status documentation in cache.txt spaces were
tabify'd.

Requested-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
This commit is contained in:
Mike Snitzer 2014-01-09 16:04:12 -05:00
parent f164e6900f
commit 6a388618f1
2 changed files with 37 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
Documentation/device-mapper/cache.txt
View File

@ -217,36 +217,42 @@ the characteristics of a specific policy, always request it by name.
Status Status
------ ------
<#used metadata blocks>/<#total metadata blocks> <#read hits> <#read misses> <metadata block size> <#used metadata blocks>/<#total metadata blocks>
<#write hits> <#write misses> <#demotions> <#promotions> <#blocks in cache> <cache block size> <#used cache blocks>/<#total cache blocks>
<#dirty> <#features> <features>* <#core args> <core args>* <#policy args> <#read hits> <#read misses> <#write hits> <#write misses>
<policy args>* <#demotions> <#promotions> <#dirty> <#features> <features>*
<#core args> <core args>* <#policy args> <policy args>*
#used metadata blocks : Number of metadata blocks used metadata block size : Fixed block size for each metadata block in
#total metadata blocks : Total number of metadata blocks sectors
#read hits : Number of times a READ bio has been mapped #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 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 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 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 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 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 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 from the origin
#feature args : Number of feature args to follow #feature args : Number of feature args to follow
feature args : 'writethrough' (optional) feature args : 'writethrough' (optional)
#core args : Number of core arguments (must be even) #core args : Number of core arguments (must be even)
core args : Key/value pairs for tuning the core core args : Key/value pairs for tuning the core
e.g. migration_threshold e.g. migration_threshold
#policy args : Number of policy arguments to follow (must be even) #policy args : Number of policy arguments to follow (must be even)
policy args : Key/value pairs policy args : Key/value pairs
e.g. 'sequential_threshold 1024 e.g. sequential_threshold
Messages Messages
-------- --------

16
drivers/md/dm-cache-target.c
View File

@ -2826,9 +2826,10 @@ static void cache_resume(struct dm_target *ti)
/* /*
* Status format: * Status format:
* *
* <#used metadata blocks>/<#total metadata blocks> * <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> * <#read hits> <#read misses> <#write hits> <#write misses>
* <#demotions> <#promotions> <#blocks in cache> <#dirty> * <#demotions> <#promotions> <#dirty>
* <#features> <features>* * <#features> <features>*
* <#core args> <core args> * <#core args> <core args>
* <#policy args> <policy args>* * <#policy args> <policy args>*
@ -2869,17 +2870,20 @@ static void cache_status(struct dm_target *ti, status_type_t type,
residency = policy_residency(cache->policy); residency = policy_residency(cache->policy);
DMEMIT("%llu/%llu %u %u %u %u %u %u %llu %u ", DMEMIT("%u %llu/%llu %u %llu/%llu %u %u %u %u %u %u %llu ",
(unsigned)(DM_CACHE_METADATA_BLOCK_SIZE >> SECTOR_SHIFT),
(unsigned long long)(nr_blocks_metadata - nr_free_blocks_metadata), (unsigned long long)(nr_blocks_metadata - nr_free_blocks_metadata),
(unsigned long long)nr_blocks_metadata, (unsigned long long)nr_blocks_metadata,
cache->sectors_per_block,
(unsigned long long) from_cblock(residency),
(unsigned long long) from_cblock(cache->cache_size),
(unsigned) atomic_read(&cache->stats.read_hit), (unsigned) atomic_read(&cache->stats.read_hit),
(unsigned) atomic_read(&cache->stats.read_miss), (unsigned) atomic_read(&cache->stats.read_miss),
(unsigned) atomic_read(&cache->stats.write_hit), (unsigned) atomic_read(&cache->stats.write_hit),
(unsigned) atomic_read(&cache->stats.write_miss), (unsigned) atomic_read(&cache->stats.write_miss),
(unsigned) atomic_read(&cache->stats.demotion), (unsigned) atomic_read(&cache->stats.demotion),
(unsigned) atomic_read(&cache->stats.promotion), (unsigned) atomic_read(&cache->stats.promotion),
(unsigned long long) from_cblock(residency), (unsigned long long) from_cblock(cache->nr_dirty));
cache->nr_dirty);
if (writethrough_mode(&cache->features)) if (writethrough_mode(&cache->features))
DMEMIT("1 writethrough "); DMEMIT("1 writethrough ");
@ -3129,7 +3133,7 @@ static void cache_io_hints(struct dm_target *ti, struct queue_limits *limits)
static struct target_type cache_target = { static struct target_type cache_target = {
.name = "cache", .name = "cache",
.version = {1, 2, 0}, .version = {1, 3, 0},
.module = THIS_MODULE, .module = THIS_MODULE,
.ctr = cache_ctr, .ctr = cache_ctr,
.dtr = cache_dtr, .dtr = cache_dtr,