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https://github.com/Zygo/bees/issues/91 describes problems encountered when running bees on systems with many CPU cores. Limit the computed number of threads (using --thread-factor or the default) to a maximum of 8 (i.e. the number of logical cores in a modern laptop). Users can override the limit by using --thread-count. Signed-off-by: Zygo Blaxell <bees@furryterror.org>
99 lines
3.3 KiB
Markdown
99 lines
3.3 KiB
Markdown
# bees Command Line Options
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## Load management options
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* `--thread-count COUNT` or `-c`
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Specify maximum number of worker threads. Overrides `--thread-factor`
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(`-C`), default/autodetected values, and the hardcoded thread limit.
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* `--thread-factor FACTOR` or `-C`
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Specify ratio of worker threads to detected CPU cores. Overridden by
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`--thread-count` (`-c`).
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Default is 1.0, i.e. 1 worker thread per detected CPU. Use values
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below 1.0 to leave some cores idle, or above 1.0 if there are more
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disks than CPUs in the filesystem.
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If the computed thread count is higher than `BEES_DEFAULT_THREAD_LIMIT`
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(currently 8), then only that number of threads will be created.
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This limit can be overridden by the `--thread-count` option; however,
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be aware that there are [kernel issues with systems that have many CPU
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cores](btrfs-kernel.md) when users try to run bees on all of them.
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* `--loadavg-target LOADAVG` or `-g`
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Specify load average target for dynamic worker threads. Default is
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to run the maximum number of worker threads all the time.
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Worker threads will be started or stopped subject to the upper limit
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imposed by `--thread-factor`, `--thread-min` and `--thread-count`
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until the load average is within +/- 0.5 of `LOADAVG`.
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* `--thread-min COUNT` or `-G`
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Specify minimum number of dynamic worker threads. This can be used
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to force a minimum number of threads to continue running while using
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`--loadavg-target` to manage load.
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Default is 0, i.e. all bees worker threads will stop when the system
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load exceeds the target.
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Has no effect unless `--loadavg-target` is used to specify a target load.
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## Filesystem tree traversal options
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* `--scan-mode MODE` or `-m`
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Specify extent scanning algorithm. Default `MODE` is 0.
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**EXPERIMENTAL** feature that may go away.
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* Mode 0: scan extents in ascending order of (inode, subvol, offset).
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Keeps shared extents between snapshots together. Reads files sequentially.
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Minimizes temporary space usage.
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* Mode 1: scan extents from all subvols in parallel. Good performance
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on non-spinning media when subvols are unrelated.
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* Mode 2: scan all extents from one subvol at a time. Good sequential
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read performance for spinning media. Maximizes temporary space usage.
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## Workarounds
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* `--workaround-btrfs-send` or `-a`
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Pretend that read-only snapshots are empty and silently discard any
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request to dedupe files referenced through them. This is a workaround for
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[problems with the kernel implementation of `btrfs send` and `btrfs send
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-p`](btrfs-kernel.md) which make these btrfs features unusable with bees.
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This option should be used to avoid breaking `btrfs send` on the same
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filesystem.
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**Note:** There is a _significant_ space tradeoff when using this option:
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it is likely no space will be recovered--and possibly significant extra
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space used--until the read-only snapshots are deleted. On the other
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hand, if snapshots are rotated frequently then bees will spend less time
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scanning them.
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## Logging options
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* `--timestamps` or `-t`
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Enable timestamps in log output.
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* `--no-timestamps` or `-T`
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Disable timestamps in log output.
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* `--absolute-paths` or `-p`
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Paths in log output will be absolute.
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* `--strip-paths` or `-P`
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Paths in log output will have the working directory at bees startup stripped.
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* `--verbose` or `-v`
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Set log verbosity (0 = no output, 8 = all output, default 8).
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