Revision 2d9efc9ab2475876270741f0592da13eef44096b authored by Cheng Chang on 12 March 2020, 01:36:43 UTC, committed by Facebook GitHub Bot on 12 March 2020, 01:40:05 UTC
Summary: In Linux, when reopening DB with many SST files, profiling shows that 100% system cpu time spent for a couple of seconds for `GetLogicalBufferSize`. This slows down MyRocks' recovery time when site is down. This PR introduces two new APIs: 1. `Env::RegisterDbPaths` and `Env::UnregisterDbPaths` lets `DB` tell the env when it starts or stops using its database directories . The `PosixFileSystem` takes this opportunity to set up a cache from database directories to the corresponding logical block sizes. 2. `LogicalBlockSizeCache` is defined only for OS_LINUX to cache the logical block sizes. Other modifications: 1. rename `logical buffer size` to `logical block size` to be consistent with Linux terms. 2. declare `GetLogicalBlockSize` in `PosixHelper` to expose it to `PosixFileSystem`. 3. change the functions `IOError` and `IOStatus` in `env/io_posix.h` to have external linkage since they are used in other translation units too. Pull Request resolved: https://github.com/facebook/rocksdb/pull/6457 Test Plan: 1. A new unit test is added for `LogicalBlockSizeCache` in `env/io_posix_test.cc`. 2. A new integration test is added for `DB` operations related to the cache in `db/db_logical_block_size_cache_test.cc`. `make check` Differential Revision: D20131243 Pulled By: cheng-chang fbshipit-source-id: 3077c50f8065c0bffb544d8f49fb10bba9408d04
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ROCKSDB_LITE.md
# RocksDBLite
RocksDBLite is a project focused on mobile use cases, which don't need a lot of fancy things we've built for server workloads and they are very sensitive to binary size. For that reason, we added a compile flag ROCKSDB_LITE that comments out a lot of the nonessential code and keeps the binary lean.
Some examples of the features disabled by ROCKSDB_LITE:
* compiled-in support for LDB tool
* No backupable DB
* No support for replication (which we provide in form of TransactionalIterator)
* No advanced monitoring tools
* No special-purpose memtables that are highly optimized for specific use cases
* No Transactions
When adding a new big feature to RocksDB, please add ROCKSDB_LITE compile guard if:
* Nobody from mobile really needs your feature,
* Your feature is adding a lot of weight to the binary.
Don't add ROCKSDB_LITE compile guard if:
* It would introduce a lot of code complexity. Compile guards make code harder to read. It's a trade-off.
* Your feature is not adding a lot of weight.
If unsure, ask. :)
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