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26983d6fa7
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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| Makefile.am | ||
| zdb_il.c | ||
| zdb.c | ||
| zdb.h | ||