Signed-off-by: Kent Overstreet <koverstreet@xxxxxxxxxx> --- Documentation/ABI/testing/sysfs-block-bcache | 156 ++++++++++++++++ Documentation/bcache.txt | 255 ++++++++++++++++++++++++++ drivers/md/Kconfig | 2 + drivers/md/Makefile | 1 + drivers/md/bcache/Kconfig | 41 ++++ drivers/md/bcache/Makefile | 14 ++ include/linux/cgroup_subsys.h | 6 + include/linux/sched.h | 4 + kernel/fork.c | 4 + 9 files changed, 483 insertions(+), 0 deletions(-) create mode 100644 Documentation/ABI/testing/sysfs-block-bcache create mode 100644 Documentation/bcache.txt create mode 100644 drivers/md/bcache/Kconfig create mode 100644 drivers/md/bcache/Makefile diff --git a/Documentation/ABI/testing/sysfs-block-bcache b/Documentation/ABI/testing/sysfs-block-bcache new file mode 100644 index 0000000..9e4bbc5 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-block-bcache @@ -0,0 +1,156 @@ +What: /sys/block/<disk>/bcache/unregister +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + A write to this file causes the backing device or cache to be + unregistered. If a backing device had dirty data in the cache, + writeback mode is automatically disabled and all dirty data is + flushed before the device is unregistered. Caches unregister + all associated backing devices before unregistering themselves. + +What: /sys/block/<disk>/bcache/clear_stats +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + Writing to this file resets all the statistics for the device. + +What: /sys/block/<disk>/bcache/cache +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + For a backing device that has cache, a symlink to + the bcache/ dir of that cache. + +What: /sys/block/<disk>/bcache/cache_hits +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + For backing devices: integer number of full cache hits, + counted per bio. A partial cache hit counts as a miss. + +What: /sys/block/<disk>/bcache/cache_misses +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + For backing devices: integer number of cache misses. + +What: /sys/block/<disk>/bcache/cache_hit_ratio +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + For backing devices: cache hits as a percentage. + +What: /sys/block/<disk>/bcache/sequential_cutoff +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + For backing devices: Threshold past which sequential IO will + skip the cache. Read and written as bytes in human readable + units (i.e. echo 10M > sequntial_cutoff). + +What: /sys/block/<disk>/bcache/bypassed +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + Sum of all reads and writes that have bypassed the cache (due + to the sequential cutoff). Expressed as bytes in human + readable units. + +What: /sys/block/<disk>/bcache/writeback +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + For backing devices: When on, writeback caching is enabled and + writes will be buffered in the cache. When off, caching is in + writethrough mode; reads and writes will be added to the + cache but no write buffering will take place. + +What: /sys/block/<disk>/bcache/writeback_running +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + For backing devices: when off, dirty data will not be written + from the cache to the backing device. The cache will still be + used to buffer writes until it is mostly full, at which point + writes transparently revert to writethrough mode. Intended only + for benchmarking/testing. + +What: /sys/block/<disk>/bcache/writeback_delay +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + For backing devices: In writeback mode, when dirty data is + written to the cache and the cache held no dirty data for that + backing device, writeback from cache to backing device starts + after this delay, expressed as an integer number of seconds. + +What: /sys/block/<disk>/bcache/writeback_percent +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + For backing devices: If nonzero, writeback from cache to + backing device only takes place when more than this percentage + of the cache is used, allowing more write coalescing to take + place and reducing total number of writes sent to the backing + device. Integer between 0 and 40. + +What: /sys/block/<disk>/bcache/synchronous +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + For a cache, a boolean that allows synchronous mode to be + switched on and off. In synchronous mode all writes are ordered + such that the cache can reliably recover from unclean shutdown; + if disabled bcache will not generally wait for writes to + complete but if the cache is not shut down cleanly all data + will be discarded from the cache. Should not be turned off with + writeback caching enabled. + +What: /sys/block/<disk>/bcache/discard +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + For a cache, a boolean allowing discard/TRIM to be turned off + or back on if the device supports it. + +What: /sys/block/<disk>/bcache/bucket_size +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + For a cache, bucket size in human readable units, as set at + cache creation time; should match the erase block size of the + SSD for optimal performance. + +What: /sys/block/<disk>/bcache/nbuckets +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + For a cache, the number of usable buckets. + +What: /sys/block/<disk>/bcache/tree_depth +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + For a cache, height of the btree excluding leaf nodes (i.e. a + one node tree will have a depth of 0). + +What: /sys/block/<disk>/bcache/btree_cache_size +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + Number of btree buckets/nodes that are currently cached in + memory; cache dynamically grows and shrinks in response to + memory pressure from the rest of the system. + +What: /sys/block/<disk>/bcache/written +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + For a cache, total amount of data in human readable units + written to the cache, excluding all metadata. + +What: /sys/block/<disk>/bcache/btree_written +Date: November 2010 +Contact: Kent Overstreet <kent.overstreet@xxxxxxxxx> +Description: + For a cache, sum of all btree writes in human readable units. diff --git a/Documentation/bcache.txt b/Documentation/bcache.txt new file mode 100644 index 0000000..270c734 --- /dev/null +++ b/Documentation/bcache.txt @@ -0,0 +1,255 @@ +Say you've got a big slow raid 6, and an X-25E or three. Wouldn't it be +nice if you could use them as cache... Hence bcache. + +Userspace tools and a wiki are at: + git://evilpiepirate.org/~kent/bcache-tools.git + http://bcache.evilpiepirate.org + +It's designed around the performance characteristics of SSDs - it only allocates +in erase block sized buckets, and it uses a hybrid btree/log to track cached +extants (which can be anywhere from a single sector to the bucket size). It's +designed to avoid random writes at all costs; it fills up an erase block +sequentially, then issues a discard before reusing it. + +Both writethrough and writeback caching are supported. Writeback defaults to +off, but can be switched on and off arbitrarily at runtime. Bcache goes to +great lengths to protect your data - it reliably handles unclean shutdown. (It +doesn't even have a notion of a clean shutdown; bcache simply doesn't return +writes as completed until they're on stable storage). + +Writeback caching can use most of the cache for buffering writes - writing +dirty data to the backing device is always done sequentially, scanning from the +start to the end of the index. + +Since random IO is what SSDs excel at, there generally won't be much benefit +to caching large sequential IO. Bcache detects sequential IO and skips it; +it also keeps a rolling average of the IO sizes per task, and as long as the +average is above the cutoff it will skip all IO from that task - instead of +caching the first 512k after every seek. Backups and large file copies should +thus entirely bypass the cache. + +In the event of a data IO error on the flash it will try to recover by reading +from disk or invalidating cache entries. For unrecoverable errors (meta data +or dirty data), caching is automatically disabled; if dirty data was present +in the cache it first disables writeback caching and waits for all dirty data +to be flushed. + +Getting started: +You'll need make-bcache from the bcache-tools repository. Both the cache device +and backing device must be formatted before use. + make-bcache -B /dev/sdb + make-bcache -C -w2k -b1M -j64 /dev/sdc + +To make bcache devices known to the kernel, echo them to /sys/fs/bcache/register: + echo /dev/sdb > /sys/fs/bcache/register + echo /dev/sdc > /sys/fs/bcache/register + +To register your bcache devices automatically, you could add something like +this to an init script: + echo /dev/sd* > /sys/fs/bcache/register_quiet + +It'll look for bcache superblocks and ignore everything that doesn't have one. + +When you register a backing device, you'll get a new /dev/bcache# device: + mkfs.ext4 /dev/bcache0 + mount /dev/bcache0 /mnt + +Cache devices are managed as sets; multiple caches per set isn't supported yet +but will allow for mirroring of metadata and dirty data in the future. Your new +cache set shows up as /sys/fs/bcache/<UUID> + +To enable caching, you need to attach the backing device to the cache set by +specifying the UUID: + echo <UUID> > /sys/block/sdb/bcache/attach + +The cache set with that UUID need not be registered to attach to it - the UUID +will be saved to the backing device's superblock and it'll start being cached +when the cache set does show up. + +This only has to be done once. The next time you reboot, just reregister all +your bcache devices. If a backing device has data in a cache somewhere, the +/dev/bcache# device won't be created until the cache shows up - particularly +important if you have writeback caching turned on. + +If you're booting up and your cache device is gone and never coming back, you +can force run the backing device: + echo 1 > /sys/block/sdb/bcache/running + +The backing device will still use that cache set if it shows up in the future, +but all the cached data will be invalidated. If there was dirty data in the +cache, don't expect the filesystem to be recoverable - you will have massive +filesystem corruption, though ext4's fsck does work miracles. + + +Other sysfs files for the backing device: + + bypassed + Sum of all IO, reads and writes, than have bypassed the cache + + cache_hits + cache_misses + cache_hit_ratio + Hits and misses are counted per individual IO as bcache sees them; a + partial hit is counted as a miss. + + cache_miss_collisions + Count of times a read completes but the data is already in the cache and + is therefore redundant. This is usually caused by readahead while a + read to the same location occurs. + + cache_readaheads + Count of times readahead occured. + + clear_stats + Writing to this file resets all the statistics. + + flush_delay_ms + flush_delay_ms_sync + Optional delay for btree writes to allow for more coalescing of updates to + the index. Default to 0. + + label + Name of underlying device. + + readahead + Size of readahead that should be performed. Defaults to 0. If set to e.g. + 1M, it will round cache miss reads up to that size, but without overlapping + existing cache entries. + + running + 1 if bcache is running. + + sequential_cutoff + A sequential IO will bypass the cache once it passes this threshhold; the + most recent 128 IOs are tracked so sequential IO can be detected even when + it isn't all done at once. + + sequential_cutoff_average + If the weighted average from a client is higher than this cutoff we bypass + all IO. + + unregister + Writing to this file disables caching on that device + + writeback + Boolean, if off only writethrough caching is done + + writeback_delay + When dirty data is written to the cache and it previously did not contain + any, waits some number of seconds before initiating writeback. Defaults to + 30. + + writeback_percent + To allow for more buffering of random writes, writeback only proceeds when + more than this percentage of the cache is unavailable. Defaults to 0. + + writeback_running + If off, writeback of dirty data will not take place at all. Dirty data will + still be added to the cache until it is mostly full; only meant for + benchmarking. Defaults to on. + +For the cache set: + active_journal_entries + Number of journal entries that are newer than the index. + + average_key_size + Average data per key in the btree. + + average_seconds_between_gc + How often garbage collection is occuring. + + block_size + Block size of the virtual device. + + btree_avg_keys_written + Average number of keys per write to the btree when a node wasn't being + rewritten - indicates how much coalescing is taking place. + + + btree_cache_size + Number of btree buckets currently cached in memory + + btree_nodes + Total nodes in the btree. + + btree_used_percent + Average fraction of btree in use. + + bucket_size + Size of Buckets + + bypassed + Sum of all IO, reads and writes, than have bypassed the cache + + cache_available_percent + Percentage of cache device free. + + clear_stats + Clears the statistics associated with this cache + + dirty_data + How much dirty data is in the cache. + + gc_ms_max + Longest garbage collection. + + internal/bset_tree_stats + internal/btree_cache_max_chain + Internal. Statistics about the bset tree and chain length. Likely to be + hidden soon. + + io_error_halflife + io_error_limit + These determines how many errors we accept before disabling the cache. + Each error is decayed by the half life (in # ios). If the decaying count + reaches io_error_limit dirty data is written out and the cache is disabled. + + root_usage_percent + Percentage of the root btree node in use. If this gets too high the node + will split, increasing the tree depth. + + seconds_since_gc + When was the last garbage collection. + + synchronous + Boolean; when on all writes to the cache are strictly ordered such that it + can recover from unclean shutdown. If off it will not generally wait for + writes to complete, but the entire cache contents will be invalidated on + unclean shutdown. Not recommended that it be turned off when writeback is + on. + + tree_depth + Depth of the btree. + + trigger_gc + Force garbage collection to run now. + + unregister + Closes the cache device and all devices being cached; if dirty data is + present it will disable writeback caching and wait for it to be flushed. + + +For each cache within a cache set: + btree_written + Sum of all btree writes, in (kilo/mega/giga) bytes + + discard + Boolean; if on a discard/TRIM will be issued to each bucket before it is + reused. Defaults to on if supported. + + io_errors + Number of errors that have occured, decayed by io_error_halflife. + + metadata_written + Total Metadata written (btree + other meta data). + + 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. + + written + Sum of all data that has been written to the cache; comparison with + btree_written gives the amount of write inflation in bcache. diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig index 10f122a..d977b45 100644 --- a/drivers/md/Kconfig +++ b/drivers/md/Kconfig @@ -185,6 +185,8 @@ config MD_FAULTY In unsure, say N. +source "drivers/md/bcache/Kconfig" + config BLK_DEV_DM tristate "Device mapper support" ---help--- diff --git a/drivers/md/Makefile b/drivers/md/Makefile index 8b2e0df..0d4b86b 100644 --- a/drivers/md/Makefile +++ b/drivers/md/Makefile @@ -26,6 +26,7 @@ obj-$(CONFIG_MD_RAID10) += raid10.o obj-$(CONFIG_MD_RAID456) += raid456.o obj-$(CONFIG_MD_MULTIPATH) += multipath.o obj-$(CONFIG_MD_FAULTY) += faulty.o +obj-$(CONFIG_BCACHE) += bcache/ obj-$(CONFIG_BLK_DEV_MD) += md-mod.o obj-$(CONFIG_BLK_DEV_DM) += dm-mod.o obj-$(CONFIG_DM_BUFIO) += dm-bufio.o diff --git a/drivers/md/bcache/Kconfig b/drivers/md/bcache/Kconfig new file mode 100644 index 0000000..9acd870 --- /dev/null +++ b/drivers/md/bcache/Kconfig @@ -0,0 +1,41 @@ + +config BCACHE + tristate "Block device as cache" + select CLOSURES + ---help--- + Allows a block device to be used as cache for other devices; uses + a btree for indexing and the layout is optimized for SSDs. + + See Documentation/bcache.txt for details. + +config BCACHE_DEBUG + bool "Bcache debugging" + depends on BCACHE + ---help--- + Don't select this option unless you're a developer + + Enables extra debugging tools (primarily a fuzz tester) + +config BCACHE_EDEBUG + bool "Extended runtime checks" + depends on BCACHE + ---help--- + Don't select this option unless you're a developer + + Enables extra runtime checks which significantly affect performance + +config BCACHE_LATENCY_DEBUG + bool "Latency tracing for bcache" + depends on BCACHE + ---help--- + Hacky latency tracing that has nevertheless been useful in the past: + adds a global variable accessible via /sys/fs/bcache/latency_warn_ms, + which defaults to 0. If nonzero, any timed operation that takes longer + emits a printk. + +config CGROUP_BCACHE + bool "Cgroup controls for bcache" + depends on BCACHE && BLK_CGROUP + ---help--- + TODO + diff --git a/drivers/md/bcache/Makefile b/drivers/md/bcache/Makefile new file mode 100644 index 0000000..0e5305d --- /dev/null +++ b/drivers/md/bcache/Makefile @@ -0,0 +1,14 @@ + +obj-$(CONFIG_BCACHE) += bcache.o + +bcache-y := alloc.o btree.o bset.o io.o journal.o\ + writeback.o movinggc.o request.o super.o debug.o util.o trace.o stats.o + +CFLAGS_alloc.o += -std=gnu99 +CFLAGS_btree.o += -std=gnu99 +CFLAGS_bset.o += -std=gnu99 +CFLAGS_journal.o += -std=gnu99 +CFLAGS_movinggc.o += -std=gnu99 +CFLAGS_request.o += -std=gnu99 -Iblock +CFLAGS_super.o += -std=gnu99 +CFLAGS_debug.o += -std=gnu99 diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h index 0bd390c..d698634 100644 --- a/include/linux/cgroup_subsys.h +++ b/include/linux/cgroup_subsys.h @@ -72,3 +72,9 @@ SUBSYS(net_prio) #endif /* */ + +#ifdef CONFIG_CGROUP_BCACHE +SUBSYS(bcache) +#endif + +/* */ diff --git a/include/linux/sched.h b/include/linux/sched.h index 4a1f493..1741596 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1583,6 +1583,10 @@ struct task_struct { struct uprobe_task *utask; int uprobe_srcu_id; #endif +#if defined(CONFIG_BCACHE) || defined(CONFIG_BCACHE_MODULE) + unsigned int sequential_io; + unsigned int sequential_io_avg; +#endif }; /* Future-safe accessor for struct task_struct's cpus_allowed. */ diff --git a/kernel/fork.c b/kernel/fork.c index f00e319..d47494b 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1314,6 +1314,10 @@ static struct task_struct *copy_process(unsigned long clone_flags, p->memcg_batch.do_batch = 0; p->memcg_batch.memcg = NULL; #endif +#ifdef CONFIG_BCACHE + p->sequential_io = 0; + p->sequential_io_avg = 0; +#endif /* Perform scheduler related setup. Assign this task to a CPU. */ sched_fork(p); -- 1.7.7.3 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
