Islam AbdelRahman f5177c761f Remove wasteful instrumentation in FullMerge (stacked on D59577)
Summary:
[ This diff is stacked on top of D59577 ]

We keep calling timer.ElapsedNanos() on every call to MergeOperator::FullMerge even when statistics are disabled, this is wasteful.

I run the readseq benchmark on a DB containing 100K merge operands for 100K keys (1 operand per key) with 1GB block cache
I see slight performance improvment

Original results

```
$ ./db_bench --benchmarks="readseq,readseq,readseq,readseq,readseq,readseq,readseq,readseq,readseq" --merge_operator="max" --merge_keys=100000 --num=100000 --db="/dev/shm/100K_merge_compacted/" --cache_size=1073741824 --use_existing_db --disable_auto_compactions
------------------------------------------------
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.498 micros/op 2006597 ops/sec;  222.0 MB/s
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.295 micros/op 3393627 ops/sec;  375.4 MB/s
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.285 micros/op 3511155 ops/sec;  388.4 MB/s
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.286 micros/op 3500470 ops/sec;  387.2 MB/s
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.283 micros/op 3530751 ops/sec;  390.6 MB/s
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.289 micros/op 3464811 ops/sec;  383.3 MB/s
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.277 micros/op 3612814 ops/sec;  399.7 MB/s
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.283 micros/op 3539640 ops/sec;  391.6 MB/s
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.285 micros/op 3503766 ops/sec;  387.6 MB/s
```

After patch

```
$ ./db_bench --benchmarks="readseq,readseq,readseq,readseq,readseq,readseq,readseq,readseq,readseq" --merge_operator="max" --merge_keys=100000 --num=100000 --db="/dev/shm/100K_merge_compacted/" --cache_size=1073741824 --use_existing_db --disable_auto_compactions
------------------------------------------------
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.476 micros/op 2100119 ops/sec;  232.3 MB/s
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.278 micros/op 3600887 ops/sec;  398.4 MB/s
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.275 micros/op 3636698 ops/sec;  402.3 MB/s
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.271 micros/op 3691661 ops/sec;  408.4 MB/s
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.273 micros/op 3661534 ops/sec;  405.1 MB/s
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.276 micros/op 3627106 ops/sec;  401.3 MB/s
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.272 micros/op 3682635 ops/sec;  407.4 MB/s
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.266 micros/op 3758331 ops/sec;  415.8 MB/s
DB path: [/dev/shm/100K_merge_compacted/]
readseq      :       0.266 micros/op 3761907 ops/sec;  416.2 MB/s
```

Test Plan: make check -j64

Reviewers: yhchiang, sdong

Reviewed By: sdong

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D59583
2016-06-13 16:22:14 -07:00
..
2016-05-17 13:11:56 -07:00
2016-05-17 13:11:56 -07:00
2016-06-09 19:03:10 -07:00
2016-06-09 19:03:10 -07:00
2016-05-09 11:52:28 -07:00
2016-04-28 17:50:58 -07:00
2016-05-09 11:52:28 -07:00
2016-06-09 19:03:10 -07:00
2016-03-18 15:18:42 -07:00
2016-05-17 13:11:56 -07:00