580fede347
Summary:
This patch bump the counters in the frequent code path DBIter::Next() / DBIter::Prev() in a local data members and send them to Statistics when the iterator is destroyed
A better solution will be to have thread_local implementation for Statistics
New performance
```
readseq : 0.035 micros/op 28597881 ops/sec; 3163.7 MB/s
1,851,568,819 stalled-cycles-frontend # 31.29% frontend cycles idle [49.86%]
884,929,823 stalled-cycles-backend # 14.95% backend cycles idle [50.21%]
readreverse : 0.071 micros/op 14077393 ops/sec; 1557.3 MB/s
3,239,575,993 stalled-cycles-frontend # 27.36% frontend cycles idle [49.96%]
1,558,253,983 stalled-cycles-backend # 13.16% backend cycles idle [50.14%]
```
Existing performance
```
readreverse : 0.174 micros/op 5732342 ops/sec; 634.1 MB/s
20,570,209,389 stalled-cycles-frontend # 70.71% frontend cycles idle [50.01%]
18,422,816,837 stalled-cycles-backend # 63.33% backend cycles idle [50.04%]
readseq : 0.119 micros/op 8400537 ops/sec; 929.3 MB/s
15,634,225,844 stalled-cycles-frontend # 79.07% frontend cycles idle [49.96%]
14,227,427,453 stalled-cycles-backend # 71.95% backend cycles idle [50.09%]
```
Test Plan: unit tests
Reviewers: yhchiang, sdong, igor
Reviewed By: sdong
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D55107
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/