12 Commits (1567108fc10e50c68f6d9df1223c1c6e2d6aab2e)

Author	SHA1	Message	Date
Peter Dillinger	459969e993	Simplify detection of x86 CPU features (#11419) ... Summary: **Background** - runtime detection of certain x86 CPU features was added for optimizing CRC32c checksums, where performance is dramatically affected by the availability of certain CPU instructions and code using intrinsics for those instructions. And Java builds with native library try to be broadly compatible but performant. What has changed is that CRC32c is no longer the most efficient cheecksum on contemporary x86_64 hardware, nor the default checksum. XXH3 is generally faster and not as dramatically impacted by the availability of certain CPU instructions. For example, on my Skylake system using db_bench (similar on an older Skylake system without AVX512): PORTABLE=1 empty USE_SSE : xxh3->8 GB/s crc32c->0.8 GB/s (no SSE4.2 nor AVX2 instructions) PORTABLE=1 USE_SSE=1 : xxh3->19 GB/s crc32c->16 GB/s (with SSE4.2 and AVX2) PORTABLE=0 USE_SSE ignored: xxh3->28 GB/s crc32c->16 GB/s (also some AVX512) Testing a ~10 year old system, with SSE4.2 but without AVX2, crc32c is a similar speed to the new systems but xxh3 is only about half that speed, also 8GB/s like the non-AVX2 compile above. Given that xxh3 has specific optimization for AVX2, I think we can infer that that crc32c is only fastest for that ~2008-2013 period when SSE4.2 was included but not AVX2. And given that xxh3 is only about 2x slower on these systems (not like >10x slower for unoptimized crc32c), I don't think we need to invest too much in optimally adapting to these old cases. x86 hardware that doesn't support fast CRC32c is now extremely rare, so requiring a custom build to support such hardware is fine IMHO. **This change** does two related things: * Remove runtime CPU detection for optimizing CRC32c on x86. Maintaining this code is non-zero work, and compiling special code that doesn't work on the configured target instruction set for code generation is always dubious. (On the one hand we have to ensure the CRC32c code uses SSE4.2 but on the other hand we have to ensure nothing else does.) * Detect CPU features in source code, not in build scripts. Although there are some hypothetical advantages to detectiong in build scripts (compiler generality), RocksDB supports at least three build systems: make, cmake, and buck. It's not practical to support feature detection on all three, and we have suffered from missed optimization opportunities by relying on missing or incomplete detection in cmake and buck. We also depend on some components like xxhash that do source code detection anyway. **In more detail:** * `HAVE_SSE42`, `HAVE_AVX2`, and `HAVE_PCLMUL` replaced by standard macros `__SSE4_2__`, `__AVX2__`, and `__PCLMUL__`. * MSVC does not provide high fidelity defines for SSE, PCLMUL, or POPCNT, but we can infer those from `__AVX__` or `__AVX2__` in a compatibility header. In rare cases of false negative or false positive feature detection, a build engineer should be able to set defines to work around the issue. * `__POPCNT__` is another standard define, but we happen to only need it on MSVC, where it is set by that compatibility header, or can be set by the build engineer. * `PORTABLE` can be set to a CPU type, e.g. "haswell", to compile for that CPU type. * `USE_SSE` is deprecated, now equivalent to PORTABLE=haswell, which roughly approximates its old behavior. Notably, this change should enable more builds to use the AVX2-optimized Bloom filter implementation. Pull Request resolved: https://github.com/facebook/rocksdb/pull/11419 Test Plan: existing tests, CI Manual performance tests after the change match the before above (none expected with make build). We also see AVX2 optimized Bloom filter code enabled when expected, by injecting a compiler error. (Performance difference is not big on my current CPU.) Reviewed By: ajkr Differential Revision: D45489041 Pulled By: pdillinger fbshipit-source-id: 60ceb0dd2aa3b365c99ed08a8b2a087a9abb6a70	2 years ago
Peter Dillinger	68a9c186d0	FilterPolicy API changes for 7.0 (#9501) ... Summary: * Inefficient block-based filter is no longer customizable in the public API, though (for now) can still be enabled. * Removed deprecated FilterPolicy::CreateFilter() and FilterPolicy::KeyMayMatch() * Removed `rocksdb_filterpolicy_create()` from C API * Change meaning of nullptr return from GetBuilderWithContext() from "use block-based filter" to "generate no filter in this case." This is a cleaner solution to the proposal in https://github.com/facebook/rocksdb/issues/8250. * Also, when user specifies bits_per_key < 0.5, we now round this down to "no filter" because we expect a filter with >= 80% FP rate is unlikely to be worth the CPU cost of accessing it (esp with cache_index_and_filter_blocks=1 or partition_filters=1). * bits_per_key >= 0.5 and < 1.0 is still rounded up to 1.0 (for 62% FP rate) * This also gives us some support for configuring filters from OPTIONS file as currently saved: `filter_policy=rocksdb.BuiltinBloomFilter`. Opening from such an options file will enable reading filters (an improvement) but not writing new ones. (See Customizable follow-up below.) * Also removed deprecated functions * FilterBitsBuilder::CalculateNumEntry() * FilterPolicy::GetFilterBitsBuilder() * NewExperimentalRibbonFilterPolicy() * Remove default implementations of * FilterBitsBuilder::EstimateEntriesAdded() * FilterBitsBuilder::ApproximateNumEntries() * FilterPolicy::GetBuilderWithContext() * Remove support for "filter_policy=experimental_ribbon" configuration string. * Allow "filter_policy=bloomfilter:n" without bool to discourage use of block-based filter. Some pieces for https://github.com/facebook/rocksdb/issues/9389 Likely follow-up (later PRs): * Refactoring toward FilterPolicy Customizable, so that we can generate filters with same configuration as before when configuring from options file. * Remove support for user enabling block-based filter (ignore `bool use_block_based_builder`) * Some months after this change, we could even remove read support for block-based filter, because it is not critical to DB data preservation. * Make FilterBitsBuilder::FinishV2 to avoid `using FilterBitsBuilder::Finish` mess and add support for specifying a MemoryAllocator (for cache warming) Pull Request resolved: https://github.com/facebook/rocksdb/pull/9501 Test Plan: A number of obsolete tests deleted and new tests or test cases added or updated. Reviewed By: hx235 Differential Revision: D34008011 Pulled By: pdillinger fbshipit-source-id: a39a720457c354e00d5b59166b686f7f59e392aa	3 years ago
Peter Dillinger	746909ceda	Ribbon: InterleavedSolutionStorage (#7598) ... Summary: The core algorithms for InterleavedSolutionStorage and the implementation SerializableInterleavedSolution make Ribbon fast for filter queries. Example output from new unit test: Simple outside query, hot, incl hashing, ns/key: 117.796 Interleaved outside query, hot, incl hashing, ns/key: 42.2655 Bloom outside query, hot, incl hashing, ns/key: 24.0071 Also includes misc cleanup of previous Ribbon code and comments. Some TODOs and FIXMEs remain for futher work / investigation. Pull Request resolved: https://github.com/facebook/rocksdb/pull/7598 Test Plan: unit tests included (integration work and tests coming later) Reviewed By: jay-zhuang Differential Revision: D24559209 Pulled By: pdillinger fbshipit-source-id: fea483cd354ba782aea3e806f2bc96e183d59441	4 years ago
Peter Dillinger	08552b19d3	Genericize and clean up FastRange (#7436) ... Summary: A generic algorithm in progress depends on a templatized version of fastrange, so this change generalizes it and renames it to fit our style guidelines, FastRange32, FastRange64, and now FastRangeGeneric. Pull Request resolved: https://github.com/facebook/rocksdb/pull/7436 Test Plan: added a few more test cases Reviewed By: jay-zhuang Differential Revision: D23958153 Pulled By: pdillinger fbshipit-source-id: 8c3b76101653417804997e5f076623a25586f3e8	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
Peter Dillinger	8aa99fc71e	Warn on excessive keys for legacy Bloom filter with 32-bit hash (#6317) ... Summary: With many millions of keys, the old Bloom filter implementation for the block-based table (format_version <= 4) would have excessive FP rate due to the limitations of feeding the Bloom filter with a 32-bit hash. This change computes an estimated inflated FP rate due to this effect and warns in the log whenever an SST filter is constructed (almost certainly a "full" not "partitioned" filter) that exceeds 1.5x FP rate due to this effect. The detailed condition is only checked if 3 million keys or more have been added to a filter, as this should be a lower bound for common bits/key settings (< 20). Recommended remedies include smaller SST file size, using format_version >= 5 (for new Bloom filter), or using partitioned filters. This does not change behavior other than generating warnings for some constructed filters using the old implementation. Pull Request resolved: https://github.com/facebook/rocksdb/pull/6317 Test Plan: Example with warning, 15M keys @ 15 bits / key: (working_mem_size_mb is just to stop after building one filter if it's large) $ ./filter_bench -quick -impl=0 -working_mem_size_mb=1 -bits_per_key=15 -average_keys_per_filter=15000000 2>&1 | grep 'FP rate' [WARN] [/block_based/filter_policy.cc:292] Using legacy SST/BBT Bloom filter with excessive key count (15.0M @ 15bpk), causing estimated 1.8x higher filter FP rate. Consider using new Bloom with format_version>=5, smaller SST file size, or partitioned filters. Predicted FP rate %: 0.766702 Average FP rate %: 0.66846 Example without warning (150K keys): $ ./filter_bench -quick -impl=0 -working_mem_size_mb=1 -bits_per_key=15 -average_keys_per_filter=150000 2>&1 | grep 'FP rate' Predicted FP rate %: 0.422857 Average FP rate %: 0.379301 $ With more samples at 15 bits/key: 150K keys -> no warning; actual: 0.379% FP rate (baseline) 1M keys -> no warning; actual: 0.396% FP rate, 1.045x 9M keys -> no warning; actual: 0.563% FP rate, 1.485x 10M keys -> warning (1.5x); actual: 0.564% FP rate, 1.488x 15M keys -> warning (1.8x); actual: 0.668% FP rate, 1.76x 25M keys -> warning (2.4x); actual: 0.880% FP rate, 2.32x At 10 bits/key: 150K keys -> no warning; actual: 1.17% FP rate (baseline) 1M keys -> no warning; actual: 1.16% FP rate 10M keys -> no warning; actual: 1.32% FP rate, 1.13x 25M keys -> no warning; actual: 1.63% FP rate, 1.39x 35M keys -> warning (1.6x); actual: 1.81% FP rate, 1.55x At 5 bits/key: 150K keys -> no warning; actual: 9.32% FP rate (baseline) 25M keys -> no warning; actual: 9.62% FP rate, 1.03x 200M keys -> no warning; actual: 12.2% FP rate, 1.31x 250M keys -> warning (1.5x); actual: 12.8% FP rate, 1.37x 300M keys -> warning (1.6x); actual: 13.4% FP rate, 1.43x The reason for the modest inaccuracy at low bits/key is that the assumption of independence between a collision between 32-hash values feeding the filter and an FP in the filter is not quite true for implementations using "simple" logic to compute indices from the stock hash result. There's math on this in my dissertation, but I don't think it's worth the effort just for these extreme cases (> 100 million keys and low-ish bits/key). Differential Revision: D19471715 Pulled By: pdillinger fbshipit-source-id: f80c96893a09bf1152630ff0b964e5cdd7e35c68	5 years ago
Peter Dillinger	57f3032285	Allow fractional bits/key in BloomFilterPolicy (#6092) ... Summary: There's no technological impediment to allowing the Bloom filter bits/key to be non-integer (fractional/decimal) values, and it provides finer control over the memory vs. accuracy trade-off. This is especially handy in using the format_version=5 Bloom filter in place of the old one, because bits_per_key=9.55 provides the same accuracy as the old bits_per_key=10. This change not only requires refining the logic for choosing the best num_probes for a given bits/key setting, it revealed a flaw in that logic. As bits/key gets higher, the best num_probes for a cache-local Bloom filter is closer to bpk / 2 than to bpk * 0.69, the best choice for a standard Bloom filter. For example, at 16 bits per key, the best num_probes is 9 (FP rate = 0.0843%) not 11 (FP rate = 0.0884%). This change fixes and refines that logic (for the format_version=5 Bloom filter only, just in case) based on empirical tests to find accuracy inflection points between each num_probes. Although bits_per_key is now specified as a double, the new Bloom filter converts/rounds this to "millibits / key" for predictable/precise internal computations. Just in case of unforeseen compatibility issues, we round to the nearest whole number bits / key for the legacy Bloom filter, so as not to unlock new behaviors for it. Pull Request resolved: https://github.com/facebook/rocksdb/pull/6092 Test Plan: unit tests included Differential Revision: D18711313 Pulled By: pdillinger fbshipit-source-id: 1aa73295f152a995328cb846ef9157ae8a05522a	5 years ago
Peter Dillinger	f059c7d9b9	New Bloom filter implementation for full and partitioned filters (#6007) ... Summary: Adds an improved, replacement Bloom filter implementation (FastLocalBloom) for full and partitioned filters in the block-based table. This replacement is faster and more accurate, especially for high bits per key or millions of keys in a single filter. Speed The improved speed, at least on recent x86_64, comes from * Using fastrange instead of modulo (%) * Using our new hash function (XXH3 preview, added in a previous commit), which is much faster for large keys and only *slightly* slower on keys around 12 bytes if hashing the same size many thousands of times in a row. * Optimizing the Bloom filter queries with AVX2 SIMD operations. (Added AVX2 to the USE_SSE=1 build.) Careful design was required to support (a) SIMD-optimized queries, (b) compatible non-SIMD code that's simple and efficient, (c) flexible choice of number of probes, and (d) essentially maximized accuracy for a cache-local Bloom filter. Probes are made eight at a time, so any number of probes up to 8 is the same speed, then up to 16, etc. * Prefetching cache lines when building the filter. Although this optimization could be applied to the old structure as well, it seems to balance out the small added cost of accumulating 64 bit hashes for adding to the filter rather than 32 bit hashes. Here's nominal speed data from filter_bench (200MB in filters, about 10k keys each, 10 bits filter data / key, 6 probes, avg key size 24 bytes, includes hashing time) on Skylake DE (relatively low clock speed): $ ./filter_bench -quick -impl=2 -net_includes_hashing # New Bloom filter Build avg ns/key: 47.7135 Mixed inside/outside queries... Single filter net ns/op: 26.2825 Random filter net ns/op: 150.459 Average FP rate %: 0.954651 $ ./filter_bench -quick -impl=0 -net_includes_hashing # Old Bloom filter Build avg ns/key: 47.2245 Mixed inside/outside queries... Single filter net ns/op: 63.2978 Random filter net ns/op: 188.038 Average FP rate %: 1.13823 Similar build time but dramatically faster query times on hot data (63 ns to 26 ns), and somewhat faster on stale data (188 ns to 150 ns). Performance differences on batched and skewed query loads are between these extremes as expected. The only other interesting thing about speed is "inside" (query key was added to filter) vs. "outside" (query key was not added to filter) query times. The non-SIMD implementations are substantially slower when most queries are "outside" vs. "inside". This goes against what one might expect or would have observed years ago, as "outside" queries only need about two probes on average, due to short-circuiting, while "inside" always have num_probes (say 6). The problem is probably the nastily unpredictable branch. The SIMD implementation has few branches (very predictable) and has pretty consistent running time regardless of query outcome. Accuracy The generally improved accuracy (re: Issue https://github.com/facebook/rocksdb/issues/5857) comes from a better design for probing indices within a cache line (re: Issue https://github.com/facebook/rocksdb/issues/4120) and improved accuracy for millions of keys in a single filter from using a 64-bit hash function (XXH3p). Design details in code comments. Accuracy data (generalizes, except old impl gets worse with millions of keys): Memory bits per key: FP rate percent old impl -> FP rate percent new impl 6: 5.70953 -> 5.69888 8: 2.45766 -> 2.29709 10: 1.13977 -> 0.959254 12: 0.662498 -> 0.411593 16: 0.353023 -> 0.0873754 24: 0.261552 -> 0.0060971 50: 0.225453 -> ~0.00003 (less than 1 in a million queries are FP) Fixes https://github.com/facebook/rocksdb/issues/5857 Fixes https://github.com/facebook/rocksdb/issues/4120 Unlike the old implementation, this implementation has a fixed cache line size (64 bytes). At 10 bits per key, the accuracy of this new implementation is very close to the old implementation with 128-byte cache line size. If there's sufficient demand, this implementation could be generalized. Compatibility Although old releases would see the new structure as corrupt filter data and read the table as if there's no filter, we've decided only to enable the new Bloom filter with new format_version=5. This provides a smooth path for automatic adoption over time, with an option for early opt-in. Pull Request resolved: https://github.com/facebook/rocksdb/pull/6007 Test Plan: filter_bench has been used thoroughly to validate speed, accuracy, and correctness. Unit tests have been carefully updated to exercise new and old implementations, as well as the logic to select an implementation based on context (format_version). Differential Revision: D18294749 Pulled By: pdillinger fbshipit-source-id: d44c9db3696e4d0a17caaec47075b7755c262c5f	5 years ago
sdong	c06b54d0c6	Apply formatter on recent 45 commits. (#5827) ... Summary: Some recent commits might not have passed through the formatter. I formatted recent 45 commits. The script hangs for more commits so I stopped there. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5827 Test Plan: Run all existing tests. Differential Revision: D17483727 fbshipit-source-id: af23113ee63015d8a43d89a3bc2c1056189afe8f	5 years ago
Peter Dillinger	68626249c3	Refactor/consolidate legacy Bloom implementation details (#5784) ... Summary: Refactoring to consolidate implementation details of legacy Bloom filters. This helps to organize and document some related, obscure code. Also added make/cpp var TEST_CACHE_LINE_SIZE so that it's easy to compile and run unit tests for non-native cache line size. (Fixed a related test failure in db_properties_test.) Pull Request resolved: https://github.com/facebook/rocksdb/pull/5784 Test Plan: make check, including Recently added Bloom schema unit tests (in ./plain_table_db_test && ./bloom_test), and including with TEST_CACHE_LINE_SIZE=128U and TEST_CACHE_LINE_SIZE=256U. Tested the schema tests with temporary fault injection into new implementations. Some performance testing with modified unit tests suggest a small to moderate improvement in speed. Differential Revision: D17381384 Pulled By: pdillinger fbshipit-source-id: ee42586da996798910fc45ac0b6289147f16d8df	5 years ago
Peter Dillinger	d3a6726f02	Revert changes from PR#5784 accidentally in PR#5780 (#5810) ... Summary: This will allow us to fix history by having the code changes for PR#5784 properly attributed to it. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5810 Differential Revision: D17400231 Pulled By: pdillinger fbshipit-source-id: 2da8b1cdf2533cfedb35b5526eadefb38c291f09	5 years ago
Peter Dillinger	aa2486b23c	Refactor some confusing logic in PlainTableReader ... Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/5780 Test Plan: existing plain table unit test Differential Revision: D17368629 Pulled By: pdillinger fbshipit-source-id: f25409cdc2f39ebe8d5cbb599cf820270e6b5d26	5 years ago