ba3c58cab6
Summary: if we enable SSE42 globally when compiling the tree for preparing a portable binary, which could be running on CPU w/o SSE42 instructions even the GCC on the building host is able to emit SSE42 code, this leads to illegal instruction errors on machines not supporting SSE42. to solve this problem, crc32 detects the supported instruction at runtime, and selects the supported CRC32 implementation according to the result of `cpuid`. but intrinics like "_mm_crc32_u64()" will not be available unless the "target" machine is appropriately specified in the command line, like "-msse42", or using the "target" attribute. we could pass "-msse42" only when compiling crc32c.cc, and allow the compiler to generate the SSE42 instructions, but we are still at the risk of executing illegal instructions on machines does not support SSE42 if the compiler emits code that is not guarded by our runtime detection. and we need to do the change in both Makefile and CMakefile. or, we can use GCC's "target" attribute to enable the machine specific instructions on certain function. in this way, we have finer grained control of the used "target". and no need to change the makefiles. so we don't need to duplicate the changes on both makefile and cmake as the previous approach. this problem surfaces when preparing a package for GNU/Linux distribution, and we only applies to optimization for SSE42, so using a feature only available on GCC/Clang is not that formidable. Closes https://github.com/facebook/rocksdb/pull/2807 Differential Revision: D5786084 Pulled By: siying fbshipit-source-id: bca5c0f877b8d6fb55f58f8f122254a26422843d
RocksDB: A Persistent Key-Value Store for Flash and RAM Storage
RocksDB is developed and maintained by Facebook Database Engineering Team. It is built on earlier work on LevelDB by Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com)
This code is a library that forms the core building block for a fast key value server, especially suited for storing data on flash drives. It has a Log-Structured-Merge-Database (LSM) design with flexible tradeoffs between Write-Amplification-Factor (WAF), Read-Amplification-Factor (RAF) and Space-Amplification-Factor (SAF). It has multi-threaded compactions, making it specially suitable for storing multiple terabytes of data in a single database.
Start with example usage here: https://github.com/facebook/rocksdb/tree/master/examples
See the github wiki for more explanation.
The public interface is in include/. Callers should not include or
rely on the details of any other header files in this package. Those
internal APIs may be changed without warning.
Design discussions are conducted in https://www.facebook.com/groups/rocksdb.dev/