11 Commits (57abdea38992350bd1d9044ddee263205a4b37f3)

Author	SHA1	Message	Date
Peter Dillinger	9f7801c5f1	Major Cache refactoring, CPU efficiency improvement (#10975) ... Summary: This is several refactorings bundled into one to avoid having to incrementally re-modify uses of Cache several times. Overall, there are breaking changes to Cache class, and it becomes more of low-level interface for implementing caches, especially block cache. New internal APIs make using Cache cleaner than before, and more insulated from block cache evolution. Hopefully, this is the last really big block cache refactoring, because of rather effectively decoupling the implementations from the uses. This change also removes the EXPERIMENTAL designation on the SecondaryCache support in Cache. It seems reasonably mature at this point but still subject to change/evolution (as I warn in the API docs for Cache). The high-level motivation for this refactoring is to minimize code duplication / compounding complexity in adding SecondaryCache support to HyperClockCache (in a later PR). Other benefits listed below. * static_cast lines of code +29 -35 (net removed 6) * reinterpret_cast lines of code +6 -32 (net removed 26) ## cache.h and secondary_cache.h * Always use CacheItemHelper with entries instead of just a Deleter. There are several motivations / justifications: * Simpler for implementations to deal with just one Insert and one Lookup. * Simpler and more efficient implementation because we don't have to track which entries are using helpers and which are using deleters * Gets rid of hack to classify cache entries by their deleter. Instead, the CacheItemHelper includes a CacheEntryRole. This simplifies a lot of code (cache_entry_roles.h almost eliminated). Fixes https://github.com/facebook/rocksdb/issues/9428. * Makes it trivial to adjust SecondaryCache behavior based on kind of block (e.g. don't re-compress filter blocks). * It is arguably less convenient for many direct users of Cache, but direct users of Cache are now rare with introduction of typed_cache.h (below). * I considered and rejected an alternative approach in which we reduce customizability by assuming each secondary cache compatible value starts with a Slice referencing the uncompressed block contents (already true or mostly true), but we apparently intend to stack secondary caches. Saving an entry from a compressed secondary to a lower tier requires custom handling offered by SaveToCallback, etc. * Make CreateCallback part of the helper and introduce CreateContext to work with it (alternative to https://github.com/facebook/rocksdb/issues/10562). This cleans up the interface while still allowing context to be provided for loading/parsing values into primary cache. This model works for async lookup in BlockBasedTable reader (reader owns a CreateContext) under the assumption that it always waits on secondary cache operations to finish. (Otherwise, the CreateContext could be destroyed while async operation depending on it continues.) This likely contributes most to the observed performance improvement because it saves an std::function backed by a heap allocation. * Use char* for serialized data, e.g. in SaveToCallback, where void* was confusingly used. (We use `char*` for serialized byte data all over RocksDB, with many advantages over `void*`. `memcpy` etc. are legacy APIs that should not be mimicked.) * Add a type alias Cache::ObjectPtr = void*, so that we can better indicate the intent of the void* when it is to be the object associated with a Cache entry. Related: started (but did not complete) a refactoring to move away from "value" of a cache entry toward "object" or "obj". (It is confusing to call Cache a key-value store (like DB) when it is really storing arbitrary in-memory objects, not byte strings.) * Remove unnecessary key param from DeleterFn. This is good for efficiency in HyperClockCache, which does not directly store the cache key in memory. (Alternative to https://github.com/facebook/rocksdb/issues/10774) * Add allocator to Cache DeleterFn. This is a kind of future-proofing change in case we get more serious about using the Cache allocator for memory tracked by the Cache. Right now, only the uncompressed block contents are allocated using the allocator, and a pointer to that allocator is saved as part of the cached object so that the deleter can use it. (See CacheAllocationPtr.) If in the future we are able to "flatten out" our Cache objects some more, it would be good not to have to track the allocator as part of each object. * Removes legacy `ApplyToAllCacheEntries` and changes `ApplyToAllEntries` signature for Deleter->CacheItemHelper change. ## typed_cache.h Adds various "typed" interfaces to the Cache as internal APIs, so that most uses of Cache can use simple type safe code without casting and without explicit deleters, etc. Almost all of the non-test, non-glue code uses of Cache have been migrated. (Follow-up work: CompressedSecondaryCache deserves deeper attention to migrate.) This change expands RocksDB's internal usage of metaprogramming and SFINAE (https://en.cppreference.com/w/cpp/language/sfinae). The existing usages of Cache are divided up at a high level into these new interfaces. See updated existing uses of Cache for examples of how these are used. * PlaceholderCacheInterface - Used for making cache reservations, with entries that have a charge but no value. * BasicTypedCacheInterface<TValue> - Used for primary cache storage of objects of type TValue, which can be cleaned up with std::default_delete<TValue>. The role is provided by TValue::kCacheEntryRole or given in an optional template parameter. * FullTypedCacheInterface<TValue, TCreateContext> - Used for secondary cache compatible storage of objects of type TValue. In addition to BasicTypedCacheInterface constraints, we require TValue::ContentSlice() to return persistable data. This simplifies usage for the normal case of simple secondary cache compatibility (can give you a Slice to the data already in memory). In addition to TCreateContext performing the role of Cache::CreateContext, it is also expected to provide a factory function for creating TValue. * For each of these, there's a "Shared" version (e.g. FullTypedSharedCacheInterface) that holds a shared_ptr to the Cache, rather than assuming external ownership by holding only a raw `Cache*`. These interfaces introduce specific handle types for each interface instantiation, so that it's easy to see what kind of object is controlled by a handle. (Ultimately, this might not be worth the extra complexity, but it seems OK so far.) Note: I attempted to make the cache 'charge' automatically inferred from the cache object type, such as by expecting an ApproximateMemoryUsage() function, but this is not so clean because there are cases where we need to compute the charge ahead of time and don't want to re-compute it. ## block_cache.h This header is essentially the replacement for the old block_like_traits.h. It includes various things to support block cache access with typed_cache.h for block-based table. ## block_based_table_reader.cc Before this change, accessing the block cache here was an awkward mix of static polymorphism (template TBlocklike) and switch-case on a dynamic BlockType value. This change mostly unifies on static polymorphism, relying on minor hacks in block_cache.h to distinguish variants of Block. We still check BlockType in some places (especially for stats, which could be improved in follow-up work) but at least the BlockType is a static constant from the template parameter. (No more awkward partial redundancy between static and dynamic info.) This likely contributes to the overall performance improvement, but hasn't been tested in isolation. The other key source of simplification here is a more unified system of creating block cache objects: for directly populating from primary cache and for promotion from secondary cache. Both use BlockCreateContext, for context and for factory functions. ## block_based_table_builder.cc, cache_dump_load_impl.cc Before this change, warming caches was super ugly code. Both of these source files had switch statements to basically transition from the dynamic BlockType world to the static TBlocklike world. None of that mess is needed anymore as there's a new, untyped WarmInCache function that handles all the details just as promotion from SecondaryCache would. (Fixes `TODO akanksha: Dedup below code` in block_based_table_builder.cc.) ## Everything else Mostly just updating Cache users to use new typed APIs when reasonably possible, or changed Cache APIs when not. Pull Request resolved: https://github.com/facebook/rocksdb/pull/10975 Test Plan: tests updated Performance test setup similar to https://github.com/facebook/rocksdb/issues/10626 (by cache size, LRUCache when not "hyper" for HyperClockCache): 34MB 1thread base.hyper -> kops/s: 0.745 io_bytes/op: 2.52504e+06 miss_ratio: 0.140906 max_rss_mb: 76.4844 34MB 1thread new.hyper -> kops/s: 0.751 io_bytes/op: 2.5123e+06 miss_ratio: 0.140161 max_rss_mb: 79.3594 34MB 1thread base -> kops/s: 0.254 io_bytes/op: 1.36073e+07 miss_ratio: 0.918818 max_rss_mb: 45.9297 34MB 1thread new -> kops/s: 0.252 io_bytes/op: 1.36157e+07 miss_ratio: 0.918999 max_rss_mb: 44.1523 34MB 32thread base.hyper -> kops/s: 7.272 io_bytes/op: 2.88323e+06 miss_ratio: 0.162532 max_rss_mb: 516.602 34MB 32thread new.hyper -> kops/s: 7.214 io_bytes/op: 2.99046e+06 miss_ratio: 0.168818 max_rss_mb: 518.293 34MB 32thread base -> kops/s: 3.528 io_bytes/op: 1.35722e+07 miss_ratio: 0.914691 max_rss_mb: 264.926 34MB 32thread new -> kops/s: 3.604 io_bytes/op: 1.35744e+07 miss_ratio: 0.915054 max_rss_mb: 264.488 233MB 1thread base.hyper -> kops/s: 53.909 io_bytes/op: 2552.35 miss_ratio: 0.0440566 max_rss_mb: 241.984 233MB 1thread new.hyper -> kops/s: 62.792 io_bytes/op: 2549.79 miss_ratio: 0.044043 max_rss_mb: 241.922 233MB 1thread base -> kops/s: 1.197 io_bytes/op: 2.75173e+06 miss_ratio: 0.103093 max_rss_mb: 241.559 233MB 1thread new -> kops/s: 1.199 io_bytes/op: 2.73723e+06 miss_ratio: 0.10305 max_rss_mb: 240.93 233MB 32thread base.hyper -> kops/s: 1298.69 io_bytes/op: 2539.12 miss_ratio: 0.0440307 max_rss_mb: 371.418 233MB 32thread new.hyper -> kops/s: 1421.35 io_bytes/op: 2538.75 miss_ratio: 0.0440307 max_rss_mb: 347.273 233MB 32thread base -> kops/s: 9.693 io_bytes/op: 2.77304e+06 miss_ratio: 0.103745 max_rss_mb: 569.691 233MB 32thread new -> kops/s: 9.75 io_bytes/op: 2.77559e+06 miss_ratio: 0.103798 max_rss_mb: 552.82 1597MB 1thread base.hyper -> kops/s: 58.607 io_bytes/op: 1449.14 miss_ratio: 0.0249324 max_rss_mb: 1583.55 1597MB 1thread new.hyper -> kops/s: 69.6 io_bytes/op: 1434.89 miss_ratio: 0.0247167 max_rss_mb: 1584.02 1597MB 1thread base -> kops/s: 60.478 io_bytes/op: 1421.28 miss_ratio: 0.024452 max_rss_mb: 1589.45 1597MB 1thread new -> kops/s: 63.973 io_bytes/op: 1416.07 miss_ratio: 0.0243766 max_rss_mb: 1589.24 1597MB 32thread base.hyper -> kops/s: 1436.2 io_bytes/op: 1357.93 miss_ratio: 0.0235353 max_rss_mb: 1692.92 1597MB 32thread new.hyper -> kops/s: 1605.03 io_bytes/op: 1358.04 miss_ratio: 0.023538 max_rss_mb: 1702.78 1597MB 32thread base -> kops/s: 280.059 io_bytes/op: 1350.34 miss_ratio: 0.023289 max_rss_mb: 1675.36 1597MB 32thread new -> kops/s: 283.125 io_bytes/op: 1351.05 miss_ratio: 0.0232797 max_rss_mb: 1703.83 Almost uniformly improving over base revision, especially for hot paths with HyperClockCache, up to 12% higher throughput seen (1597MB, 32thread, hyper). The improvement for that is likely coming from much simplified code for providing context for secondary cache promotion (CreateCallback/CreateContext), and possibly from less branching in block_based_table_reader. And likely a small improvement from not reconstituting key for DeleterFn. Reviewed By: anand1976 Differential Revision: D42417818 Pulled By: pdillinger fbshipit-source-id: f86bfdd584dce27c028b151ba56818ad14f7a432	2 years ago
akankshamahajan	0e7b27bfcf	Refactor block cache tracing APIs (#10811) ... Summary: Refactor the classes, APIs and data structures for block cache tracing to allow a user provided trace writer to be used. Currently, only a TraceWriter is supported, with a default built-in implementation of FileTraceWriter. The TraceWriter, however, takes a flat trace record and is thus only suitable for file tracing. This PR introduces an abstract BlockCacheTraceWriter class that takes a structured BlockCacheTraceRecord. The BlockCacheTraceWriter implementation can then format and log the record in whatever way it sees fit. The default BlockCacheTraceWriterImpl does file tracing using a user provided TraceWriter. `DB::StartBlockTrace` will internally redirect to changed `BlockCacheTrace::StartBlockCacheTrace`. New API `DB::StartBlockTrace` is also added that directly takes `BlockCacheTraceWriter` pointer. This same philosophy can be applied to KV and IO tracing as well. Pull Request resolved: https://github.com/facebook/rocksdb/pull/10811 Test Plan: existing unit tests Old API DB::StartBlockTrace checked with db_bench tool create database ``` ./db_bench --benchmarks="fillseq" \ --key_size=20 --prefix_size=20 --keys_per_prefix=0 --value_size=100 \ --cache_index_and_filter_blocks --cache_size=1048576 \ --disable_auto_compactions=1 --disable_wal=1 --compression_type=none \ --min_level_to_compress=-1 --compression_ratio=1 --num=10000000 ``` To trace block cache accesses when running readrandom benchmark: ``` ./db_bench --benchmarks="readrandom" --use_existing_db --duration=60 \ --key_size=20 --prefix_size=20 --keys_per_prefix=0 --value_size=100 \ --cache_index_and_filter_blocks --cache_size=1048576 \ --disable_auto_compactions=1 --disable_wal=1 --compression_type=none \ --min_level_to_compress=-1 --compression_ratio=1 --num=10000000 \ --threads=16 \ -block_cache_trace_file="/tmp/binary_trace_test_example" \ -block_cache_trace_max_trace_file_size_in_bytes=1073741824 \ -block_cache_trace_sampling_frequency=1 ``` Reviewed By: anand1976 Differential Revision: D40435289 Pulled By: akankshamahajan15 fbshipit-source-id: fa2755f4788185e19f4605e731641cfd21ab3282	2 years ago
Merlin Mao	f58d276764	Make TraceRecord and Replayer public (#8611) ... Summary: New public interfaces: `TraceRecord` and `TraceRecord::Handler`, available in "rocksdb/trace_record.h". `Replayer`, available in `rocksdb/utilities/replayer.h`. User can use `DB::NewDefaultReplayer()` to create a Replayer to auto/manual replay a trace file. Unit tests: - `./db_test2 --gtest_filter="DBTest2.TraceAndReplay"`: Updated with the internal API changes. - `./db_test2 --gtest_filter="DBTest2.TraceAndManualReplay"`: New for manual replay. Pull Request resolved: https://github.com/facebook/rocksdb/pull/8611 Reviewed By: ajkr Differential Revision: D30266329 Pulled By: autopear fbshipit-source-id: 1ecb3cbbedae0f6a67c18f0cc82e002b4d81b6f8	3 years ago
mrambacher	b7e1c5213f	Add some simulator cache and block tracer tests to ASSERT_STATUS_CHECKED (#7305) ... Summary: More tests now pass. When in doubt, I added a TODO comment to check what should happen with an ignored error. Pull Request resolved: https://github.com/facebook/rocksdb/pull/7305 Reviewed By: akankshamahajan15 Differential Revision: D23301262 Pulled By: ajkr fbshipit-source-id: 5f120edc7393560aefc0633250277bbc7e8de9e6	4 years ago
sdong	fdf882ded2	Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) ... Summary: When dynamically linking two binaries together, different builds of RocksDB from two sources might cause errors. To provide a tool for user to solve the problem, the RocksDB namespace is changed to a flag which can be overridden in build time. Pull Request resolved: https://github.com/facebook/rocksdb/pull/6433 Test Plan: Build release, all and jtest. Try to build with ROCKSDB_NAMESPACE with another flag. Differential Revision: D19977691 fbshipit-source-id: aa7f2d0972e1c31d75339ac48478f34f6cfcfb3e	5 years ago
haoyuhuang	e648c1d9eb	Cache simulator: Optimize hybrid row-block cache. (#5616) ... Summary: This PR optimizes the hybrid row-block cache simulator. If a Get request hits the cache, we treat all its future accesses as hits. Consider a Get request (no snapshot) accesses multiple files, e.g, file1, file2, file3. We construct the row key as "fdnumber_key_0". Before this PR, if it hits the cache when searching the key in file1, we continue to process its accesses in file2 and file3 which is unnecessary. With this PR, if "file1_key_0" is in the cache, we treat all future accesses of this Get request as hits. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5616 Differential Revision: D16453187 Pulled By: HaoyuHuang fbshipit-source-id: 56f3169cc322322305baaf5543226a0824fae19f	5 years ago
haoyuhuang	3778470061	Block cache analyzer: Compute correlation of features and human readable trace file. (#5596) ... Summary: - Compute correlation between a few features and predictions, e.g., number of accesses since the last access vs number of accesses till the next access on a block. - Output human readable trace file so python can consume it. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5596 Test Plan: make clean && USE_CLANG=1 make check -j32 Differential Revision: D16373200 Pulled By: HaoyuHuang fbshipit-source-id: c848d26bc2e9210461f317d7dbee42d55be5a0cc	5 years ago
haoyuhuang	8a008d4170	Block access tracing: Trace referenced key for Get on non-data blocks. (#5548) ... Summary: This PR traces the referenced key for Get for all types of blocks. This is useful when evaluating hybrid row-block caches. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5548 Test Plan: make clean && USE_CLANG=1 make check -j32 Differential Revision: D16157979 Pulled By: HaoyuHuang fbshipit-source-id: f6327411c9deb74e35e22a35f66cdbae09ab9d87	5 years ago
haoyuhuang	1a59b6e2a9	Cache simulator: Add a ghost cache for admission control and a hybrid row-block cache. (#5534) ... Summary: This PR adds a ghost cache for admission control. Specifically, it admits an entry on its second access. It also adds a hybrid row-block cache that caches the referenced key-value pairs of a Get/MultiGet request instead of its blocks. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5534 Test Plan: make clean && COMPILE_WITH_ASAN=1 make check -j32 Differential Revision: D16101124 Pulled By: HaoyuHuang fbshipit-source-id: b99edda6418a888e94eb40f71ece45d375e234b1	5 years ago
haoyuhuang	6ca3feed5c	Fix -Werror=shadow (#5546) ... Summary: This PR fixes shadow errors. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5546 Test Plan: make clean && make check -j32 && make clean && USE_CLANG=1 make check -j32 && make clean && COMPILE_WITH_ASAN=1 make check -j32 Differential Revision: D16147841 Pulled By: HaoyuHuang fbshipit-source-id: 1043500d70c134185f537ab4c3900452752f1534	5 years ago
haoyuhuang	9f0bd56889	Cache simulator: Refactor the cache simulator so that we can add alternative policies easily (#5517) ... Summary: This PR creates cache_simulator.h file. It contains a CacheSimulator that runs against a block cache trace record. We can add alternative cache simulators derived from CacheSimulator later. For example, this PR adds a PrioritizedCacheSimulator that inserts filter/index/uncompressed dictionary blocks with high priority. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5517 Test Plan: make clean && COMPILE_WITH_ASAN=1 make check -j32 Differential Revision: D16043689 Pulled By: HaoyuHuang fbshipit-source-id: 65f28ed52b866ffb0e6eceffd7f9ca7c45bb680d	5 years ago