Reorder field based on esan data
Summary:
Running. TEST_TMPDIR=/dev/shm ./buck-out/gen/rocks/tools/rocks_db_bench --benchmarks=readwhilewriting --num=5000000 -benchmark_write_rate_limit=2000000 --threads=32
Collected esan data and reorder field. Accesses to 4th and 6th fields take majority of the access. Group them. Overall, this struct takes 10%+ of the total accesses in the program. (637773011/6107964986)
==2433831== class rocksdb::InlineSkipList
==2433831== size = 48, count = 637773011, ratio = 112412, array access = 0
==2433831== # 0: offset = 0, size = 2, count = 455137, type = i16
==2433831== # 1: offset = 2, size = 2, count = 6, type = i16
==2433831== # 2: offset = 4, size = 4, count = 182303, type = i32
==2433831== # 3: offset = 8, size = 8, count = 263953900, type = %"class.rocksdb::MemTableRep::KeyComparator"*
==2433831== # 4: offset = 16, size = 8, count = 136409, type = %"class.rocksdb::Allocator"*
==2433831== # 5: offset = 24, size = 8, count = 366628820, type = %"struct.rocksdb::InlineSkipList<const rocksdb::MemTableRep::KeyComparator &>::Node"*
==2433831== # 6: offset = 32, size = 4, count = 6280031, type = %"struct.std::atomic" = type { %"struct.std::__atomic_base" }
==2433831== # 7: offset = 40, size = 8, count = 136405, type = %"struct.rocksdb::InlineSkipList<const rocksdb::MemTableRep::KeyComparator &>::Splice"*
==2433831==EfficiencySanitizer: total struct field access count = 6107964986
Before re-ordering
[trentxintong@devbig460.frc2 ~/fbsource/fbcode]$ fgrep readwhilewriting
without-ro.log
readwhilewriting : 0.036 micros/op 27545605 ops/sec; 26.8 MB/s
(45954 of 5000000 found)
readwhilewriting : 0.036 micros/op 28024240 ops/sec; 27.2 MB/s
(43158 of 5000000 found)
readwhilewriting : 0.037 micros/op 27345145 ops/sec; 27.1 MB/s
(46725 of 5000000 found)
readwhilewriting : 0.037 micros/op 27072588 ops/sec; 27.3 MB/s
(42605 of 5000000 found)
readwhilewriting : 0.034 micros/op 29578781 ops/sec; 28.3 MB/s
(44294 of 5000000 found)
readwhilewriting : 0.035 micros/op 28528304 ops/sec; 27.7 MB/s
(44176 of 5000000 found)
readwhilewriting : 0.037 micros/op 27075497 ops/sec; 26.5 MB/s
(43763 of 5000000 found)
readwhilewriting : 0.036 micros/op 28024117 ops/sec; 27.1 MB/s
(40622 of 5000000 found)
readwhilewriting : 0.037 micros/op 27078709 ops/sec; 27.6 MB/s
(47774 of 5000000 found)
readwhilewriting : 0.034 micros/op 29020689 ops/sec; 28.1 MB/s
(45066 of 5000000 found)
AVERAGE()=27.37 MB/s
After re-ordering
[trentxintong@devbig460.frc2 ~/fbsource/fbcode]$ fgrep readwhilewriting
ro.log
readwhilewriting : 0.036 micros/op 27542409 ops/sec; 27.7 MB/s
(46163 of 5000000 found)
readwhilewriting : 0.036 micros/op 28021148 ops/sec; 28.2 MB/s
(46155 of 5000000 found)
readwhilewriting : 0.036 micros/op 28021035 ops/sec; 27.3 MB/s
(44039 of 5000000 found)
readwhilewriting : 0.036 micros/op 27538659 ops/sec; 27.5 MB/s
(46781 of 5000000 found)
readwhilewriting : 0.036 micros/op 28028604 ops/sec; 27.6 MB/s
(44689 of 5000000 found)
readwhilewriting : 0.036 micros/op 27541452 ops/sec; 27.3 MB/s
(43156 of 5000000 found)
readwhilewriting : 0.034 micros/op 29041338 ops/sec; 28.8 MB/s
(44895 of 5000000 found)
readwhilewriting : 0.036 micros/op 27784974 ops/sec; 26.3 MB/s
(39963 of 5000000 found)
readwhilewriting : 0.036 micros/op 27538892 ops/sec; 28.1 MB/s
(46570 of 5000000 found)
readwhilewriting : 0.038 micros/op 26622473 ops/sec; 27.0 MB/s
(43236 of 5000000 found)
AVERAGE()=27.58 MB/s
Closes https://github.com/facebook/rocksdb/pull/3855
Reviewed By: siying
Differential Revision: D8048781
Pulled By: trentxintong
fbshipit-source-id: bc9807a9845e2a92cb171ce1ecb5a2c8a51f1481
aed7abbcca