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The use of the VM shrinker was a bad fit for locks. Shrinking a lock requires a round trip with the server to request a null mode. The VM treats the locks like a cache, as expected, which leads to huge amounts of locks accumulating and then being shrank in bulk. This creates a huge backlog of locks making their way through the network conversation with the server that implements invalidating to a null mode and freeing. It starves other network and lock processing, possibly for minutes. This removes the VM shrinker and instead introduces an option that sets a limit on the number of idle locks. As the number of locks exceeds the count we only try to free an oldest lock at each lock call. This results in a lock freeing pace that is proportional to the allocation of new locks by callers and so is throttled by the work done while callers hold locks. It avoids the bulk shrinking of 10s of thousands of locks that we see in the field. Signed-off-by: Zach Brown <zab@versity.com>
Introduction
scoutfs is a clustered in-kernel Linux filesystem designed to support large archival systems. It features additional interfaces and metadata so that archive agents can perform their maintenance workflows without walking all the files in the namespace. Its cluster support lets deployments add nodes to satisfy archival tier bandwidth targets.
The design goal is to reach file populations in the trillions, with the archival bandwidth to match, while remaining operational and responsive.
Highlights of the design and implementation include:
- Fully consistent POSIX semantics between nodes
- Atomic transactions to maintain consistent persistent structures
- Integrated archival metadata replaces syncing to external databases
- Dynamic seperation of resources lets nodes write in parallel
- 64bit throughout; no limits on file or directory sizes or counts
- Open GPLv2 implementation
Community Mailing List
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