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Summary: The current BlobDB garbage collection logic works by relocating the valid blobs from the oldest blob files as they are encountered during compaction, and cleaning up blob files once they contain nothing but garbage. However, with sufficiently skewed workloads, it is theoretically possible to end up in a situation when few or no compactions get scheduled for the SST files that contain references to the oldest blob files, which can lead to increased space amp due to the lack of GC. In order to efficiently handle such workloads, the patch adds a new BlobDB configuration option called `blob_garbage_collection_force_threshold`, which signals to BlobDB to schedule targeted compactions for the SST files that keep alive the oldest batch of blob files if the overall ratio of garbage in the given blob files meets the threshold *and* all the given blob files are eligible for GC based on `blob_garbage_collection_age_cutoff`. (For example, if the new option is set to 0.9, targeted compactions will get scheduled if the sum of garbage bytes meets or exceeds 90% of the sum of total bytes in the oldest blob files, assuming all affected blob files are below the age-based cutoff.) The net result of these targeted compactions is that the valid blobs in the oldest blob files are relocated and the oldest blob files themselves cleaned up (since *all* SST files that rely on them get compacted away). These targeted compactions are similar to periodic compactions in the sense that they force certain SST files that otherwise would not get picked up to undergo compaction and also in the sense that instead of merging files from multiple levels, they target a single file. (Note: such compactions might still include neighboring files from the same level due to the need of having a "clean cut" boundary but they never include any files from any other level.) This functionality is currently only supported with the leveled compaction style and is inactive by default (since the default value is set to 1.0, i.e. 100%). Pull Request resolved: https://github.com/facebook/rocksdb/pull/8994 Test Plan: Ran `make check` and tested using `db_bench` and the stress/crash tests. Reviewed By: riversand963 Differential Revision: D31489850 Pulled By: ltamasi fbshipit-source-id: 44057d511726a0e2a03c5d9313d7511b3f0c4eab |
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| .. | ||
| batched_ops_stress.cc | ||
| cf_consistency_stress.cc | ||
| CMakeLists.txt | ||
| db_stress.cc | ||
| db_stress_common.cc | ||
| db_stress_common.h | ||
| db_stress_compaction_filter.h | ||
| db_stress_driver.cc | ||
| db_stress_driver.h | ||
| db_stress_env_wrapper.h | ||
| db_stress_gflags.cc | ||
| db_stress_listener.h | ||
| db_stress_shared_state.cc | ||
| db_stress_shared_state.h | ||
| db_stress_stat.h | ||
| db_stress_table_properties_collector.h | ||
| db_stress_test_base.cc | ||
| db_stress_test_base.h | ||
| db_stress_tool.cc | ||
| expected_state.cc | ||
| expected_state.h | ||
| no_batched_ops_stress.cc | ||