Bcachefs Tools 1.38.6 Brings Many Performance Improvements - Phoronix

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Bcachefs Tools 1.38.6 Brings Many Performance Improvements

Written by Michael Larabel in Linux Storage on 17 June 2026 at 04:06 PM EDT. 59 Comments

Kent Overstreet announced the release today of Bcachefs-Tools 1.38.6 as the user-space tools built around the Bcachefs copy-on-write file-system. There are a few new features and a lot of performance work in v1.38.6 without bringing any on-disk format breakage.

Bcachefs-Tools now supports up to 255 storage devices in a single file-system. There is also Ubuntu 26.04 LTS packages now published via apt.bcachefs.org to facilitate easier testing.

Plus there are many bug fixes but most significant is all the performance work that went into this release. Overstreet summed up the performance changes as:<br>"Performance work spanned much of the codebase, quite a few workloads and benchmarks were profiled. Some highlights:

- Many performance improvements in the journalling code, primarily targeting lock contention. Journal flushes are now fully lockless, significantly improving performance on multithreaded O_SYNC/fsync workloads.

Journal pin lists now have per-pin-list locks instead of sharing the main journal lock, and the journal pin fifo can now be resized at runtime; this avoids unnecessary throttling on O_SYNC/fsync heavy workloads.

Journal read now has to read significantly less of the journal by using a binary search to find the most recent entry on each device, which we're also taking advantage of by increasing the default journal size.

- The core btree iterator and transaction commit code saw significant profiling and optimization, greatly reducing icache usage in particular.

- Btree sharding was greatly improved; we now shard new inode allocations based on pid, not the current cpu, enforce that btree nodes do not cross shard boundaries, and on lock contention we try to migrate threads to the CPU for their data's shard. This drastically reduces lock contention; high client count dbench particularly benefited.

- Multithreaded btree write-buffer flushing saw more improvements, reducing stalls due to lock inversion, and runtime introspection was greatly improved."

Hopefully time at Phoronix will allow for some new Linux file-system comparison performance benchmarks soon, Bcachefs included, especially given Btrfs large folios by default and other upstream file-system improvements hitting Linux 7.2.

More details on the Bcachefs Tools 1.38.6 release via bcachefs-tools.git.

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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via MichaelLarabel.com.

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