Commit 6a388618 authored by Mike Snitzer's avatar Mike Snitzer
Browse files

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: default avatarJonathan Brassow <jbrassow@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Acked-by: default avatarJoe Thornber <ejt@redhat.com>
parent f164e690

Documentation/device-mapper/cache.txt

+28 −22
Original line number Diff line number Diff line
@@ -217,13 +217,20 @@ 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>*



<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 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
@@ -236,7 +243,6 @@ Status 
			     from the cache

#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

			     from the origin

#feature args		 : Number of feature args to follow
@@ -246,7 +252,7 @@ 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

			     e.g. sequential_threshold



Messages

--------

drivers/md/dm-cache-target.c

+10 −6
Original line number Diff line number Diff line
@@ -2826,9 +2826,10 @@ static void cache_resume(struct dm_target *ti) 
/*

 * 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>

 * <#demotions> <#promotions> <#blocks in cache> <#dirty>

 * <#demotions> <#promotions> <#dirty>

 * <#features> <features>*

 * <#core args> <core 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);



		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,

		       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_miss),

		       (unsigned) atomic_read(&cache->stats.write_hit),

		       (unsigned) atomic_read(&cache->stats.write_miss),

		       (unsigned) atomic_read(&cache->stats.demotion),

		       (unsigned) atomic_read(&cache->stats.promotion),

		       (unsigned long long) from_cblock(residency),

		       cache->nr_dirty);

		       (unsigned long long) from_cblock(cache->nr_dirty));



		if (writethrough_mode(&cache->features))

			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 = {

	.name = "cache",

	.version = {1, 2, 0},

	.version = {1, 3, 0},

	.module = THIS_MODULE,

	.ctr = cache_ctr,

	.dtr = cache_dtr,

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