Summary:
RocksDB's `Cache` abstraction currently supports two priority levels for items: high (used for frequently accessed/highly valuable SST metablocks like index/filter blocks) and low (used for SST data blocks). Blobs are typically lower-value targets for caching than data blocks, since 1) with BlobDB, data blocks containing blob references conceptually form an index structure which has to be consulted before we can read the blob value, and 2) cached blobs represent only a single key-value, while cached data blocks generally contain multiple KVs. Since we would like to make it possible to use the same backing cache for the block cache and the blob cache, it would make sense to add a new, lower-than-low cache priority level (bottom level) for blobs so data blocks are prioritized over them.
This task is a part of https://github.com/facebook/rocksdb/issues/10156
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10461
Reviewed By: siying
Differential Revision: D38672823
Pulled By: ltamasi
fbshipit-source-id: 90cf7362036563d79891f47be2cc24b827482743
Summary:
RocksDB's `Cache` abstraction currently supports two priority levels for items: high (used for frequently accessed/highly valuable SST metablocks like index/filter blocks) and low (used for SST data blocks). Blobs are typically lower-value targets for caching than data blocks, since 1) with BlobDB, data blocks containing blob references conceptually form an index structure which has to be consulted before we can read the blob value, and 2) cached blobs represent only a single key-value, while cached data blocks generally contain multiple KVs. Since we would like to make it possible to use the same backing cache for the block cache and the blob cache, it would make sense to add a new, lower-than-low cache priority level (bottom level) for blobs so data blocks are prioritized over them.
This task is a part of https://github.com/facebook/rocksdb/issues/10156
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10309
Reviewed By: ltamasi
Differential Revision: D38211655
Pulled By: gangliao
fbshipit-source-id: 65ef33337db4d85277cc6f9782d67c421ad71dd5
Summary:
Many workloads have temporal locality, where recently written items are read back in a short period of time. When using remote file systems, this is inefficient since it involves network traffic and higher latencies. Because of this, we would like to support prepopulating the blob cache during flush.
This task is a part of https://github.com/facebook/rocksdb/issues/10156
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10298
Reviewed By: ltamasi
Differential Revision: D37908743
Pulled By: gangliao
fbshipit-source-id: 9feaed234bc719d38f0c02975c1ad19fa4bb37d1
Summary:
Previously the version was displayed as $major.$minor
This changes it to $major.$minor.$path
This also adds the git hash for the time from which RocksDB was built to the end of report.tsv. I confirmed that benchmark_log_tool.py still parses it and that the people
who consume/graph these results are OK with it.
Example output:
ops_sec mb_sec lsm_sz blob_sz c_wgb w_amp c_mbps c_wsecs c_csecs b_rgb b_wgb usec_op p50 p99 p99.9 p99.99 pmax uptime stall% Nstall u_cpu s_cpu rss test date version job_id githash
609488 244.1 1GB 0.0GB, 1.4 0.7 93.3 39 38 0 0 1.6 1.0 4 15 26 5365 15 0.0 0 0.1 0.0 0.5 fillseq.wal_disabled.v400 2022-06-29T13:36:05 7.5.0 6115254416
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10277
Test Plan: Run it
Reviewed By: jay-zhuang
Differential Revision: D37532418
Pulled By: mdcallag
fbshipit-source-id: 55e472640d51265819b228d3373c9fa9b62b660d
Summary:
This adds --undefok to support use of this script with BlobDB for db_bench versions prior
to 7.5 when the options land in a release.
While there is a limit to how far back this script can go WRT backwards compatiblity,
this is an easy change to support early 7.x releases.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10276
Test Plan: Run it with versions of db_bench that do not and then do support these options
Reviewed By: gangliao
Differential Revision: D37529299
Pulled By: mdcallag
fbshipit-source-id: 7bb1feec5c68760e6d64792c585bfbde4f5e52d8
Summary:
In order to facilitate correctness and performance testing, we would like to add the new blob cache to our stress test tool `db_stress` and our continuously running crash test script `db_crashtest.py`, as well as our synthetic benchmarking tool `db_bench` and the BlobDB performance testing script `run_blob_bench.sh`.
As part of this task, we would also like to utilize these benchmarking tools to get some initial performance numbers about the effectiveness of caching blobs.
This PR is a part of https://github.com/facebook/rocksdb/issues/10156
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10202
Reviewed By: ltamasi
Differential Revision: D37325739
Pulled By: gangliao
fbshipit-source-id: deb65d0d414502270dd4c324d987fd5469869fa8
Summary:
See https://github.com/facebook/rocksdb/issues/10082 for more details. Trivial move
isn't done for universal when compaction is from L0 into L0. So a too small value for
num_levels with db_bench means there will be fewer trivial moves with universal and
that means that write-amp will increase.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10158
Test Plan: run it
Reviewed By: siying
Differential Revision: D37122519
Pulled By: mdcallag
fbshipit-source-id: 1cb39049676f68a6cc3ea8d105a9965f89d4d09e
Summary:
A recent diff add a few more fields to one of the db_bench output lines that gets parsed.
This diff updates tools/benchmark.sh to handle that.
overwrite : 7.939 micros/op 125963 ops/sec; 50.5 MB/s
overwrite : 7.854 micros/op 127320 ops/sec 1800.001 seconds 229176999 operations; 51.0 MB/s
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10124
Test Plan: Run it
Reviewed By: jay-zhuang
Differential Revision: D36945137
Pulled By: mdcallag
fbshipit-source-id: 9c96f79491411da997e369a3be9c6b921a21d0fa
Summary:
**Context/Summary:**
AdvancedColumnFamilyOptions::rate_limit_delay_max_milliseconds has been marked as deprecated and it's time to actually remove the code.
- Keep `soft_rate_limit`/`hard_rate_limit` in `cf_mutable_options_type_info` to prevent throwing `InvalidArgument` in `GetColumnFamilyOptionsFromMap` when reading an option file still with these options (e.g, old option file generated from RocksDB before the deprecation)
- Keep `soft_rate_limit`/`hard_rate_limit` in under `OptionsOldApiTest.GetOptionsFromMapTest` to test the case mentioned above.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9455
Test Plan: Rely on my eyeball and CI
Reviewed By: ajkr
Differential Revision: D33811664
Pulled By: hx235
fbshipit-source-id: 866859427fe710354a90f1095057f80116365ff0
Summary:
**Context/Summary:**
AdvancedColumnFamilyOptions::soft_rate_limit/hard_rate_limit have been marked as deprecated and it's time to actually remove the code.
- Keep `soft_rate_limit`/`hard_rate_limit` in `cf_mutable_options_type_info` to prevent throwing `InvalidArgument` in `GetColumnFamilyOptionsFromMap` when reading an option file still with these options (e.g, old option file generated from RocksDB before the deprecation)
- Keep `soft_rate_limit`/`hard_rate_limit` in under `OptionsOldApiTest.GetOptionsFromMapTest` to test the case mentioned above.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9452
Test Plan: Rely on my eyeball and CI
Reviewed By: ajkr
Differential Revision: D33804938
Pulled By: hx235
fbshipit-source-id: 133d49f7ec5238d7efceeb0a3122a5792a2b9945
Summary:
The patch adds a new BlobDB benchmarking script called `run_blob_bench.sh`.
It is a thin wrapper around `benchmark.sh` (similarly to `run_flash_bench.sh`):
it actually calls `benchmark.sh` a number of times, cycling through six workloads,
two write-only ones (bulk load and overwrite), two read/write ones (point lookups
while writing, range scans while writing), and two read-only ones (point lookups
and range scans).
Note: this is a simpler/cleaned up/reworked version of the script used to produce the
benchmark results in http://rocksdb.org/blog/2021/05/26/integrated-blob-db.html .
The new version takes advantage of several recent `benchmark.sh` improvements
like the ability to pass in arbitrary `db_bench` options or the possibility of using a
job ID.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9015
Test Plan: Ran the script manually with different parameter combinations.
Reviewed By: riversand963
Differential Revision: D31555277
Pulled By: ltamasi
fbshipit-source-id: 0e151b2f7b2cf6f66ed7f95455571492ad7ea87f
Summary:
* Started on some proper usage text to document the options
* Added a `JOB_ID` parameter, so that we can trace jobs and relate them to other assets
* Now generates a correct TSV file of the summary
* Summary has new additional fields:
* RocksDB Version
* Date
* Job ID
* db_bench log files now also include the Job ID
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8730
Reviewed By: mrambacher
Differential Revision: D30747344
Pulled By: jay-zhuang
fbshipit-source-id: 87eb78d20959b6d95804aebf129606fa9c71f407
Summary:
1. Fix printing of stats when there are no writes (wamp=0). Previously had a div0 error
2. Added multireadrandom command as a valid target
3. Added ability to pass additional command line options to db_bench. Now can say things like benchmark.sh readrandom --mmap_read and the option will be passed to db_bench.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8346
Reviewed By: zhichao-cao
Differential Revision: D29500436
Pulled By: mrambacher
fbshipit-source-id: 54e90708aae9133be3a903e35efdf8f8abbd86fa
Summary:
I guess we didn't update this script when `--allow_concurrent_memtable_write` became true by default.
Fixes#4413.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4428
Differential Revision: D10036452
Pulled By: ajkr
fbshipit-source-id: f464be0642bd096d9040f82cdc3eae614a902183
Summary: Grandfather in super old lint issues to make a clean slate for moving forward that allows us to have stronger enforcement on new issues.
Reviewed By: yiwu-arbug
Differential Revision: D6821806
fbshipit-source-id: 22797d31ec58e9eb0255d3b66fedfcfcb0dc127c
Summary:
Removed max_grandparent_overlap_factor from benchmark.sh since it is not a valid option anymore.
Closes https://github.com/facebook/rocksdb/pull/2015
Differential Revision: D4748229
Pulled By: lgalanis
fbshipit-source-id: c3869ea
Summary:
Remove disableDataSync, and another similarly named disable_data_sync options.
This is being done to simplify options, and also because the performance gains of this feature can be achieved by other methods.
Closes https://github.com/facebook/rocksdb/pull/1859
Differential Revision: D4541292
Pulled By: sagar0
fbshipit-source-id: 5b3a6ca
Summary:
This diff includes an initial script running a set of benchmarks for
regression test. The script does the following things:
checkout the specified rocksdb commit (or origin/master as default)
make clean && DEBUG_LEVEL=0 make db_bench
setup test directories
run set of benchmarks and store results
Currently, the script will run couple benchmarks, store all the benchmark
output, extract micros per op and percentile information for each benchmark
and store them in a single SUMMARY.csv file. The SUMMARY.csv will make the
follow-up regression detection easier.
In addition, the current script only takes env arguments to set important
attributes of db_bench. Will follow-up with a patch that allows db_bench
to construct options from an options file.
Test Plan:
NUM_KEYS=100 ./tools/regression_test.sh
Sample SUMMARY.csv file:
commit id, benchmark, ms-per-op, p50, p75, p99, p99.9, p99.99
7e23ddf575890510e7d2fc7a79b31a1bbf317917, fillseq, 15.28, 54.66, 77.14, 5000.00, 17900.00, 18483.00
7e23ddf575890510e7d2fc7a79b31a1bbf317917, overwrite, 13.54, 57.69, 86.39, 3000.00, 15600.00, 17013.00
7e23ddf575890510e7d2fc7a79b31a1bbf317917, readrandom, 1.04, 0.80, 1.67, 293.33, 395.00, 504.00
7e23ddf575890510e7d2fc7a79b31a1bbf317917, readwhilewriting, 2.75, 1.01, 1.87, 200.00, 460.00, 485.00
7e23ddf575890510e7d2fc7a79b31a1bbf317917, deleterandom, 3.64, 48.12, 70.09, 200.00, 336.67, 347.00
7e23ddf575890510e7d2fc7a79b31a1bbf317917, seekrandom, 24.31, 391.87, 513.69, 872.73, 990.00, 1048.00
7e23ddf575890510e7d2fc7a79b31a1bbf317917, seekrandomwhilewriting, 14.02, 185.14, 294.15, 700.00, 1440.00, 1527.00
Reviewers: sdong, IslamAbdelRahman, kradhakrishnan, yiwu, andrewkr, gunnarku
Reviewed By: gunnarku
Subscribers: gunnarku, MarkCallaghan, andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D57597
Summary:
This is taken from the "Write(GB)" column in compaction stats, so the
units should be GB, not MB.
Test Plan: none
Reviewers: sdong, yhchiang, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: leveldb, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D56889
Summary:
When a block based table file is opened, if prefetch_index_and_filter is true, it will prefetch the index and filter blocks, putting them into the block cache.
What this feature adds: when a L0 block based table file is opened, if pin_l0_filter_and_index_blocks_in_cache is true in the options (and prefetch_index_and_filter is true), then the filter and index blocks aren't released back to the block cache at the end of BlockBasedTableReader::Open(). Instead the table reader takes ownership of them, hence pinning them, ie. the LRU cache will never push them out. Meanwhile in the table reader, further accesses will not hit the block cache, thus avoiding lock contention.
Test Plan:
'export TEST_TMPDIR=/dev/shm/ && DISABLE_JEMALLOC=1 OPT=-g make all valgrind_check -j32' is OK.
I didn't run the Java tests, I don't have Java set up on my devserver.
Reviewers: sdong
Reviewed By: sdong
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D56133
Summary:
When a block based table file is opened, if prefetch_index_and_filter is true, it will prefetch the index and filter blocks, putting them into the block cache.
What this feature adds: when a L0 block based table file is opened, if pin_l0_filter_and_index_blocks_in_cache is true in the options (and prefetch_index_and_filter is true), then the filter and index blocks aren't released back to the block cache at the end of BlockBasedTableReader::Open(). Instead the table reader takes ownership of them, hence pinning them, ie. the LRU cache will never push them out. Meanwhile in the table reader, further accesses will not hit the block cache, thus avoiding lock contention.
When the table reader is destroyed, it releases the pinned blocks (if there were any). This has to happen before the cache is destroyed, so I had to introduce a TableReader::Close(), to guarantee the order of destruction.
Test Plan:
Added two unit tests for this. Existing unit tests run fine (default is pin_l0_filter_and_index_blocks_in_cache=false).
DISABLE_JEMALLOC=1 OPT=-g make all valgrind_check -j32
Mac: OK.
Linux: with D55287 patched in it's OK.
Reviewers: sdong
Reviewed By: sdong
Subscribers: andrewkr, leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D54801
Summary: For compactions benchmarks (both level and universal) we'll use `--max_write_buffer_number=4`. For all the other benchmarks which don't customize the value of `--max_background_flushes` we'll continue using `--max_write_buffer_number=8`.
Test Plan:
To validate basic correctness and command-line options:
```
cd ~/rocksdb
NKEYS=10000000 ./tools/run_flash_bench.sh
```
Reviewers: MarkCallaghan
Reviewed By: MarkCallaghan
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D55497
Summary: Set of updates to the subcompaction benchmark script which are based on our internal discussions. The intent behind the changes is to make sure that the scripts will correctly reflect how we're doing the actual benchmarking.
Test Plan: Tested by exercising the full set of compaction benchmarks and validating the execution and consistency of results.
Reviewers: MarkCallaghan, sdong, yhchiang
Reviewed By: yhchiang
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D55461
Summary: After closely working with Mark, Siying, and Yueh-Hsuan this set of changes reflects the updates needed to measure RocksDB subcompaction performance in a correct manner. The essence of the benchmark is executing `fillrandom` followed by `compact` with the correct set of options for various number of subcompactions specified.
Test Plan: Tested internally to verify correctness and reliability.
Reviewers: sdong, yhchiang, MarkCallaghan
Reviewed By: MarkCallaghan
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D55089
Summary:
Implement a benchmark for universal compaction based on the feature description (see below), in-person discussions, and reading source code:
https://github.com/facebook/rocksdb/wiki/RocksDB-Tuning-Guidehttps://github.com/facebook/rocksdb/wiki/Universal-Compactionhttps://github.com/facebook/rocksdb/wiki/RocksDB-Tuning-Guide#universal-compaction
Universal compaction benchmark is based on `overwrite` benchmark, adding compaction specific options to it, and executing it for different values of subcompaction to understand the impact of scaling out subcompactions for a particular scenario.
Test Plan:
- Execute the benchmark on various machines for multiple iterations to verify the reliability.
- Observe the output to make sure that compaction is taking place.
- Observe the execution to make sure that arguments passed to `db_bench` are correct.
Reviewers: sdong, MarkCallaghan
Reviewed By: MarkCallaghan
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D54045
Summary: This set of changes is part of the work to introduce benchmark for universal style compaction in RocksDB. It's conceptually separate from the compaction work, so sending it out as a separate diff to get it out of the way.
Test Plan:
- Run `./tools/run_flash_bench.sh`.
- Look at the contents of `report.txt` and `report2.txt` to make sure that data is reported and attributed correctly.
- During `db_bench` execution time make sure that the correct flags are passed to `--disable_wal` depending on the benchmark being executed.
Reviewers: MarkCallaghan
Reviewed By: MarkCallaghan
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D53865
Summary:
1) changes tools/{benchmark,run_flash_bench}.sh to optionally use the write rate limit
2) removes code for --writes_per_second and switches the 'background' write rate limit
to use --benchmark_write_rate_limit
Replaces https://reviews.facebook.net/D49113
Task ID: #9555881
Blame Rev:
Test Plan:
tools/run_flash_bench.sh
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
Reviewers: igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D52485
Summary:
db_bench output now displays Percentile many times with --statistics after
read IO latency histograms were added. So I only need the last one in the report output.
Task ID: #
Blame Rev:
Test Plan:
run run_flash_bench.sh
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
Reviewers: igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D45093
Summary:
Changes include:
* don't sync-on-commit for single writer thread in readwhile... tests
* make default block size 8kb rather than 4kb to avoid too small blocks after compression
* use snappy instead of zlib to avoid stalls from compression latency
* disable statistics
* use bytes_per_sync=8M to reduce throughput loss on disk
* use open_files=-1 to reduce mutex contention
Task ID: #
Blame Rev:
Test Plan:
run benchmark
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
Reviewers: igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D44961
Summary: Optimistic transactions supporting begin/commit/rollback semantics. Currently relies on checking the memtable to determine if there are any collisions at commit time. Not yet implemented would be a way of enuring the memtable has some minimum amount of history so that we won't fail to commit when the memtable is empty. You should probably start with transaction.h to get an overview of what is currently supported.
Test Plan: Added a new test, but still need to look into stress testing.
Reviewers: yhchiang, igor, rven, sdong
Reviewed By: sdong
Subscribers: adamretter, MarkCallaghan, leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D33435
Summary:
This is done to avoid having each thread use the same seed between runs
of db_bench. Without this we can inflate the OS filesystem cache hit rate on
reads for read heavy tests and generally see the same key sequences get generated
between teste runs.
Task ID: #
Blame Rev:
Test Plan:
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
Reviewers: igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D37563
Summary:
This adds:
1) use of --level_compaction_dynamic_level_bytes=true
2) use of --bytes_per_sync=2M
The second is a big win for disks. The first helps in general.
This also adds a new test, fillseq with 32kb values to increase the peak
ingest and make it more likely that storage limits throughput.
Sample outpout from the first 3 tests - https://gist.github.com/mdcallag/e793bd3038e367b05d6f
Task ID: #
Blame Rev:
Test Plan:
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
Reviewers: igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D37509
Summary:
This changes loads to use vector memtable and disable the WAL. This also
increases the chance we will see IO bottlenecks during loads which is good to stress
test HW. But I also think it is a good way to load data quickly as this is a bulk
operation and the WAL isn't needed.
The two numbers below are the MB/sec rates for fillseq, bulkload using a skiplist
or vector memtable and the WAL enabled or disabled. There is a big benefit from
using the vector memtable and WAL disabled. Alas there is also a perf bug in
the use of std::sort for ordered input when the vector is flushed. Task is open
for that.
112, 66 - skiplist with wal
250, 116 - skiplist without wal
110, 108 - vector with wal
232, 370 - vector without wal
Task ID: #
Blame Rev:
Test Plan:
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
Reviewers: igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D36957
Summary:
This adds p99.9 and p99.99 response times to the benchmark report and
adds a second report, report2.txt that has tests listed in test order rather
than the time in which they were run, so overwrite tests are listed for
all thread counts, then update etc.
Also changes fillseq to compress all levels to avoid write-amp from rewriting
uncompressed files when they reach the first level to compress.
Increase max_write_buffer_number to avoid stalls during fillseq and make
max_background_flushes agree with max_write_buffer_number.
See https://gist.github.com/mdcallag/297ff4316a25cb2988f7 for an example
of the new report (report2.txt)
Task ID: #
Blame Rev:
Test Plan:
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
Reviewers: igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D36537
Summary:
The --stats_interval_seconds determines interval for stats reporting
and overrides --stats_interval when set. I also changed tools/benchmark.sh
to report stats every 60 seconds so I can avoid trying to figure out a
good value for --stats_interval per test and per storage device.
Task ID: #6631621
Blame Rev:
Test Plan:
run tools/run_flash_bench, look at output
Revert Plan:
Database Impact:
Memcache Impact:
Other Notes:
EImportant:
- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -
Reviewers: igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D36189
Gang Liao