diff options
Diffstat (limited to 'Documentation/bcache.txt')
| -rw-r--r-- | Documentation/bcache.txt | 22 |
1 files changed, 14 insertions, 8 deletions
diff --git a/Documentation/bcache.txt b/Documentation/bcache.txt index 77db880..c3365f2 100644 --- a/Documentation/bcache.txt +++ b/Documentation/bcache.txt @@ -181,7 +181,7 @@ want for getting the best possible numbers when benchmarking. In practice this isn't an issue because as soon as a write comes along it'll cause the btree node to be split, and you need almost no write traffic for - this to not show up enough to be noticable (especially since bcache's btree + this to not show up enough to be noticeable (especially since bcache's btree nodes are huge and index large regions of the device). But when you're benchmarking, if you're trying to warm the cache by reading a bunch of data and there's no other traffic - that can be a problem. @@ -222,7 +222,7 @@ running it's in passthrough mode or caching). sequential_cutoff - A sequential IO will bypass the cache once it passes this threshhold; the + A sequential IO will bypass the cache once it passes this threshold; the most recent 128 IOs are tracked so sequential IO can be detected even when it isn't all done at once. @@ -296,7 +296,7 @@ cache_miss_collisions since the synchronization for cache misses was rewritten) cache_readaheads - Count of times readahead occured. + Count of times readahead occurred. SYSFS - CACHE SET: @@ -319,7 +319,10 @@ cache<0..n> Symlink to each of the cache devices comprising this cache set. cache_available_percent - Percentage of cache device free. + Percentage of cache device which doesn't contain dirty data, and could + potentially be used for writeback. This doesn't mean this space isn't used + for clean cached data; the unused statistic (in priority_stats) is typically + much lower. clear_stats Clears the statistics associated with this cache @@ -359,7 +362,7 @@ unregister SYSFS - CACHE SET INTERNAL: This directory also exposes timings for a number of internal operations, with -separate files for average duration, average frequency, last occurence and max +separate files for average duration, average frequency, last occurrence and max duration: garbage collection, btree read, btree node sorts and btree splits. active_journal_entries @@ -414,7 +417,7 @@ freelist_percent space. io_errors - Number of errors that have occured, decayed by io_error_halflife. + Number of errors that have occurred, decayed by io_error_halflife. metadata_written Sum of all non data writes (btree writes and all other metadata). @@ -423,8 +426,11 @@ nbuckets Total buckets in this cache priority_stats - Statistics about how recently data in the cache has been accessed. This can - reveal your working set size. + Statistics about how recently data in the cache has been accessed. + This can reveal your working set size. Unused is the percentage of + the cache that doesn't contain any data. Metadata is bcache's + metadata overhead. Average is the average priority of cache buckets. + Next is a list of quantiles with the priority threshold of each. written Sum of all data that has been written to the cache; comparison with |