Revision 4a21b1402cb454f6e68d4c6f288d73700b3ff9db authored by Islam AbdelRahman on 01 December 2016, 21:30:01 UTC, committed by Facebook Github Bot on 01 December 2016, 21:39:14 UTC
Summary:
Reduce number of comparisons in heap by caching which child node in the first level is smallest (left_child or right_child)
So next time we can compare directly against the smallest child

I see that the total number of calls to comparator drops significantly when using this optimization

Before caching (~2mil key comparison for iterating the DB)
```
$ DEBUG_LEVEL=0 make db_bench -j64 && ./db_bench --benchmarks="readseq" --db="/dev/shm/heap_opt" --use_existing_db --disable_auto_compactions --cache_size=1000000000  --perf_level=2
readseq      :       0.338 micros/op 2959201 ops/sec;  327.4 MB/s user_key_comparison_count = 2000008
```
After caching (~1mil key comparison for iterating the DB)
```
$ DEBUG_LEVEL=0 make db_bench -j64 && ./db_bench --benchmarks="readseq" --db="/dev/shm/heap_opt" --use_existing_db --disable_auto_compactions --cache_size=1000000000 --perf_level=2
readseq      :       0.309 micros/op 3236801 ops/sec;  358.1 MB/s user_key_comparison_count = 1000011
```

It also improves
Closes https://github.com/facebook/rocksdb/pull/1600

Differential Revision: D4256027

Pulled By: IslamAbdelRahman

fbshipit-source-id: 76fcc66
1 parent e39d080
History
File Mode Size
.gitignore -rw-r--r-- 6 bytes
API.md -rw-r--r-- 6.0 KB
README.md -rw-r--r-- 1.1 KB
binding.gyp -rw-r--r-- 549 bytes
db_wrapper.cc -rw-r--r-- 15.8 KB
db_wrapper.h -rw-r--r-- 2.0 KB
rdb -rwxr-xr-x 154 bytes
rdb.cc -rw-r--r-- 248 bytes
unit_test.js -rw-r--r-- 3.1 KB

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