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Currently we maintain a single LRU list of cluster locks and every time we acquire a cluster lock we move it to the head of the LRU, creating significant contention acquiring the spinlock that protects the LRU list. This moves to two LRU lists, a list of cluster locks ready to be reclaimed and one for locks that are in active use. We mark locks with which list they're on and only move them to the active list if they're on the reclaim list. We track imbalance between the two lists so that they're always roughly the same size. This removes contention maintaining a precise LRU amongst a set of active cluster locks. It doesn't address contention creating or removing locks, which are already very expensive operations. It also loses strict ordering by access time. Reclaim has to make it through the oldest half of locks before getting to the newer half, though there is no guaranteed ordering amogst the newest half. Signed-off-by: Zach Brown <zab@versity.com> Signed-off-by: Chris Kirby <ckirby@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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