[dm-devel] [PATCH v3 for-3.14] dm cache: add block sizes and total cache blocks to status output
Joe Thornber
thornber at redhat.com
Fri Jan 10 15:13:45 UTC 2014
You're determined to do this, so I'll ack the patch.
On Fri, Jan 10, 2014 at 09:10:28AM -0500, Mike Snitzer wrote:
> 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 at redhat.com>
> Signed-off-by: Mike Snitzer <snitzer at redhat.com>
> ---
> Documentation/device-mapper/cache.txt | 50 ++++++++++++++++++--------------
> drivers/md/dm-cache-target.c | 16 ++++++----
> 2 files changed, 38 insertions(+), 28 deletions(-)
>
> diff --git a/Documentation/device-mapper/cache.txt b/Documentation/device-mapper/cache.txt
> index 719320b..63fd7cf 100644
> --- a/Documentation/device-mapper/cache.txt
> +++ b/Documentation/device-mapper/cache.txt
> @@ -217,36 +217,42 @@ 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 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 args : Number of policy arguments to follow (must be even)
> +policy args : Key/value pairs
> + e.g. sequential_threshold
>
> Messages
> --------
> diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
> index 1b1469e..11ad705 100644
> --- a/drivers/md/dm-cache-target.c
> +++ b/drivers/md/dm-cache-target.c
> @@ -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,
> --
> 1.7.4.4
>
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