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f4464c6896
The crawl_master task had a simple atomic variable that was supposed to prevent duplicate crawl_master tasks from ending up in the queue; however, this had a race condition that could lead to m_task_running being set with no crawl_master task running to clear it. This would in turn prevent crawl_thread from scheduling any further crawl_master tasks, and bees would eventually stop doing any more work. A proper fix is to modify the Task class and its friends such that Task::run() guarantees that 1) at most one instance of a Task is ever scheduled or running at any time, and 2) if a Task is scheduled while an instance of the Task is running, the scheduling is deferred until after the current instance completes. This is part of a fairly large planned change set, but it's not ready to push now. So instead, unconditionally push a new crawl_master Task into the queue on every poll, then silently and quickly exit if the queue is too full or the supply of new extents is empty. Drop the scheduling-related members of BeesRoots as they will not be needed when the proper fix lands. Fixes: 4f0bc78a "crawl: don't block a Task waiting for new transids" Signed-off-by: Zygo Blaxell <bees@furryterror.org>
BEES
Best-Effort Extent-Same, a btrfs deduplication agent.
About bees
bees is a block-oriented userspace deduplication agent designed for large btrfs filesystems. It is an offline dedupe combined with an incremental data scan capability to minimize time data spends on disk from write to dedupe.
Strengths
- Space-efficient hash table and matching algorithms - can use as little as 1 GB hash table per 10 TB unique data (0.1GB/TB)
- Incremental realtime dedupe of new data using btrfs tree search
- Works with btrfs compression - dedupe any combination of compressed and uncompressed files
- NEW Works around
btrfs sendproblems with dedupe and incremental parent shapshots - Works around btrfs filesystem structure to free more disk space
- Persistent hash table for rapid restart after shutdown
- Whole-filesystem dedupe - including snapshots
- Constant hash table size - no increased RAM usage if data set becomes larger
- Works on live data - no scheduled downtime required
- Automatic self-throttling based on system load
Weaknesses
- Whole-filesystem dedupe - has no include/exclude filters, does not accept file lists
- Runs continuously as a daemon - no quick start/stop
- Requires root privilege (or
CAP_SYS_ADMIN) - First run may require temporary disk space for extent reorganization
- First run may increase metadata space usage if many snapshots exist
- Constant hash table size - no decreased RAM usage if data set becomes smaller
- btrfs only
Installation and Usage
Recommended Reading
More Information
Bug Reports and Contributions
Email bug reports and patches to Zygo Blaxell bees@furryterror.org.
You can also use Github:
https://github.com/Zygo/bees
Copyright & License
Copyright 2015-2018 Zygo Blaxell bees@furryterror.org.
GPL (version 3 or later).