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When attempting to debug performance problems on large systems, one of the major factors that affect performance is free space fragmentation. This heavily affects the allocation process, which is an area of active development in ZFS. Unfortunately, fragmenting a large pool for testing purposes is time consuming; it usually involves filling the pool and then repeatedly overwriting data until the free space becomes fragmented, which can take many hours. And even if the time is available, artificial workloads rarely generate the same fragmentation patterns as the natural workloads they're attempting to mimic. This patch has two parts. First, in zdb, we add the ability to export the full allocation map of the pool. It iterates over each vdev, printing every allocated segment in the ms_allocatable range tree. This can be done while the pool is online, though in that case the allocation map may actually be from several different TXGs as new ones are loaded on demand. The second is a new subcommand for zhack, zhack metaslab leak (and its supporting kernel changes). This is a zhack subcommand that imports a pool and then modified the range trees of the metaslabs, allowing the sync process to write them out normall. It does not currently store those allocations anywhere to make them reversible, and there is no corresponding free subcommand (which would be extremely dangerous); this is an irreversible process, only intended for performance testing. The only way to reclaim the space afterwards is to destroy the pool or roll back to a checkpoint. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Paul Dagnelie <paul.dagnelie@klarasystems.com> Sponsored-by: Klara, Inc. Sponsored-by: Wasabi Technology, Inc. Closes #17576 |
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| libzfs_core | ||
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| LICENSE | ||
| Makefile.am | ||
| README | ||
| setup.py.in | ||
This package provides a wrapper for libzfs_core C library. libzfs_core is intended to be a stable interface for programmatic administration of ZFS. This wrapper provides one-to-one wrappers for libzfs_core API functions, but the signatures and types are more natural to Python. nvlists are wrapped as dictionaries or lists depending on their usage. Some parameters have default values depending on typical use for increased convenience. Enumerations and bit flags become strings and lists of strings in Python. Errors are reported as exceptions rather than integer errno-style error codes. The wrapper takes care to provide one-to-many mapping of the error codes to the exceptions by interpreting a context in which the error code is produced. Unit tests and automated test for the libzfs_core API are provided with this package. Please note that the API tests perform lots of ZFS dataset level operations and ZFS tries hard to ensure that any modifications do reach stable storage. That means that the operations are done synchronously and that, for example, disk caches are flushed. Thus, the tests can be very slow on real hardware. It is recommended to place the default temporary directory or a temporary directory specified by, for instance, TMP environment variable on a memory backed filesystem. Package documentation: http://pyzfs.readthedocs.org Package development: https://github.com/openzfs/zfs