Commit Graph

48 Commits

Author SHA1 Message Date
Peter Dillinger
bb87164db3 Fork and simplify LRUCache for developing enhancements (#9917)
Summary:
To support a project to prototype and evaluate algorithmic
enhancments and alternatives to LRUCache, here I have separated out
LRUCache into internal-only "FastLRUCache" and cut it down to
essentials, so that details like secondary cache handling and
priorities do not interfere with prototyping. These can be
re-integrated later as needed, along with refactoring to minimize code
duplication (which would slow down prototyping for now).

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9917

Test Plan:
unit tests updated to ensure basic functionality has (likely)
been preserved

Reviewed By: anand1976

Differential Revision: D35995554

Pulled By: pdillinger

fbshipit-source-id: d67b20b7ada3b5d3bfe56d897a73885894a1d9db
2022-05-03 12:32:02 -07:00
gitbw95
f241d082b6 Prevent double caching in the compressed secondary cache (#9747)
Summary:
###  **Summary:**
When both LRU Cache and CompressedSecondaryCache are configured together, there possibly are some data blocks double cached.

**Changes include:**
1. Update IS_PROMOTED to IS_IN_SECONDARY_CACHE to prevent confusions.
2. This PR updates SecondaryCacheResultHandle and use IsErasedFromSecondaryCache to determine whether the handle is erased in the secondary cache. Then, the caller can determine whether to SetIsInSecondaryCache().
3. Rename LRUSecondaryCache to CompressedSecondaryCache.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9747

Test Plan:
**Test Scripts:**
1. Populate a DB. The on disk footprint is 482 MB. The data is set to be 50% compressible, so the total decompressed size is expected to be 964 MB.
./db_bench --benchmarks=fillrandom --num=10000000 -db=/db_bench_1

2. overwrite it to a stable state:
./db_bench --benchmarks=overwrite,stats --num=10000000 -use_existing_db -duration=10 --benchmark_write_rate_limit=2000000 -db=/db_bench_1

4. Run read tests with diffeernt cache setting:

T1:
./db_bench --benchmarks=seekrandom,stats --threads=16 --num=10000000 -use_existing_db -duration=120 --benchmark_write_rate_limit=52000000 -use_direct_reads --cache_size=520000000  --statistics -db=/db_bench_1

T2:
./db_bench --benchmarks=seekrandom,stats --threads=16 --num=10000000 -use_existing_db -duration=120 --benchmark_write_rate_limit=52000000 -use_direct_reads --cache_size=320000000 -compressed_secondary_cache_size=400000000 --statistics -use_compressed_secondary_cache -db=/db_bench_1

T3:
./db_bench --benchmarks=seekrandom,stats --threads=16 --num=10000000 -use_existing_db -duration=120 --benchmark_write_rate_limit=52000000 -use_direct_reads --cache_size=520000000 -compressed_secondary_cache_size=400000000 --statistics -use_compressed_secondary_cache -db=/db_bench_1

T4:
./db_bench --benchmarks=seekrandom,stats --threads=16 --num=10000000 -use_existing_db -duration=120 --benchmark_write_rate_limit=52000000 -use_direct_reads --cache_size=20000000 -compressed_secondary_cache_size=500000000 --statistics -use_compressed_secondary_cache -db=/db_bench_1

**Before this PR**
| Cache Size | Compressed Secondary Cache Size | Cache Hit Rate |
|------------|-------------------------------------|----------------|
|520 MB | 0 MB | 85.5% |
|320 MB | 400 MB | 96.2% |
|520 MB | 400 MB | 98.3% |
|20 MB | 500 MB | 98.8% |

**Before this PR**
| Cache Size | Compressed Secondary Cache Size | Cache Hit Rate |
|------------|-------------------------------------|----------------|
|520 MB | 0 MB | 85.5% |
|320 MB | 400 MB | 99.9% |
|520 MB | 400 MB | 99.9% |
|20 MB | 500 MB | 99.2% |

Reviewed By: anand1976

Differential Revision: D35117499

Pulled By: gitbw95

fbshipit-source-id: ea2657749fc13efebe91a8a1b56bc61d6a224a12
2022-04-11 13:28:33 -07:00
Bo Wang
bcabee737f Improve comments for some files (#9793)
Summary:
Update the comments, e.g. fixing typo, formatting, etc.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9793

Reviewed By: jay-zhuang

Differential Revision: D35323989

Pulled By: gitbw95

fbshipit-source-id: 4a72fc02b67abaae8be0d1439b68f9967a68052d
2022-04-01 16:06:14 -07:00
gitbw95
8102690a52 Update Cache::Release param from force_erase to erase_if_last_ref (#9728)
Summary:
The param name force_erase may be misleading, since the handle is erased only if it has last reference even if the param is set true.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9728

Reviewed By: pdillinger

Differential Revision: D35038673

Pulled By: gitbw95

fbshipit-source-id: 0d16d1e8fed17b97eba7fb53207119332f659a5f
2022-03-22 10:22:18 -07:00
Peter Dillinger
fc3a6eb74a Fix/improve 'must free heap allocations' code (#9209)
Summary:
Added missing include, and cleaned up to make same mistake less
likely in future (minimize conditional compilation)

Fixes https://github.com/facebook/rocksdb/issues/9183

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9209

Test Plan: added to existing test

Reviewed By: mrambacher

Differential Revision: D32631390

Pulled By: pdillinger

fbshipit-source-id: 63a0501855cf5fac9e22ca1e5c4f53725dbf3f93
2021-11-29 10:53:52 -08:00
anand76
ec9f52ece6 Fix a race in LRUCacheShard::Promote (#8717)
Summary:
In ```LRUCacheShard::Promote```, a reference is released outside the LRU mutex. Fix the race condition.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8717

Reviewed By: zhichao-cao

Differential Revision: D30649206

Pulled By: anand1976

fbshipit-source-id: 09c0af05b2294a7fe2c02876a61b0bad6e3ada61
2021-08-30 19:10:55 -07:00
anand76
f35042ca40 Add a PerfContext counter for secondary cache hits (#8685)
Summary:
Add a PerfContext counter.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8685

Reviewed By: zhichao-cao

Differential Revision: D30453957

Pulled By: anand1976

fbshipit-source-id: 42888a3ced240e1c44446d52d3b04adfb01f5665
2021-08-20 15:17:30 -07:00
anand76
add68bd28a Add a stat to count secondary cache hits (#8666)
Summary:
Add a stat for secondary cache hits. The ```Cache::Lookup``` API had an unused ```stats``` parameter. This PR uses that to pass the pointer to a ```Statistics``` object that ```LRUCache``` uses to record the stat.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8666

Test Plan: Update a unit test in lru_cache_test

Reviewed By: zhichao-cao

Differential Revision: D30353816

Pulled By: anand1976

fbshipit-source-id: 2046f78b460428877a26ffdd2bb914ae47dfbe77
2021-08-16 21:01:14 -07:00
Peter Dillinger
5ad3227650 Work around falsely reported data race on LRUHandle::flags (#8539)
Summary:
Some bits are mutated and read while holding a lock, other
immutable bits (esp. secondary cache compatibility) can be read by
arbitrary threads without holding a lock. AFAIK, this doesn't cause an
issue on any architecture we care about, because you will get some
legitimate version of the value that includes the initialization, as
long as synchronization guarantees the initialization happens before the
read.

I've only seen this in https://github.com/facebook/rocksdb/issues/8538 so far, but it should be fixed regardless.
Otherwise, we'll surely get these false reports again some time.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8539

Test Plan: some local TSAN test runs and in CircleCI

Reviewed By: zhichao-cao

Differential Revision: D29720262

Pulled By: pdillinger

fbshipit-source-id: 365fd7e565577c648815161f71b339bcb5ce12d5
2021-07-15 16:09:18 -07:00
anand76
a0cbb69421 Fix assertion failure when releasing a handle after secondary cache lookup fails (#8470)
Summary:
When the secondary cache lookup fails, we may still allocate a handle and charge the cache for metadata usage. If the cache is full, this can cause the usage to go over capacity. Later, when a (unrelated) handle is released, it trips up an assertion that checks that usage is less than capacity. To prevent this assertion failure, don't charge the cache for a failed secondary cache lookup.

Tests:
Run crash_test

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8470

Reviewed By: zhichao-cao

Differential Revision: D29474713

Pulled By: anand1976

fbshipit-source-id: 27191969c95470a7b070d292b458efce71395bf2
2021-06-30 13:29:30 -07:00
anand76
a50da404be Fix a tsan warning due to reading flags in LRUHandle without holding a mutex (#8433)
Summary:
Tsan complains due to a perceived race condition in accessing LRUHandle flags. One thread calls ```LRUHandle::SetHit()``` from ```LRUCacheShard::Lookup()```, while another thread calls ```LRUHandle::IsPending()``` from ```LRUCacheShard::IsReady()```. The latter call is from ```MultiGet```. It doesn't actually have to call ```IsReady``` since a null value indicates the cache handle is not ready, so its sufficient to check for a null value.

Also modify ```IsReady``` to acquire the LRU shard mutex.

Tests:
1. make check
2. Run tsan_crash

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8433

Reviewed By: zhichao-cao

Differential Revision: D29278030

Pulled By: anand1976

fbshipit-source-id: 0c9fed56d12eda853e72dadebe75038361bd257f
2021-06-21 21:23:56 -07:00
anand76
8ea0a2c1bd Parallelize secondary cache lookup in MultiGet (#8405)
Summary:
Implement the ```WaitAll()``` interface in ```LRUCache``` to allow callers to issue multiple lookups in parallel and wait for all of them to complete. Modify ```MultiGet``` to use this to parallelize the secondary cache lookups in order to reduce the overall latency. A call to ```cache->Lookup()``` returns a handle that has an incomplete value (nullptr), and the caller can call ```cache->IsReady()``` to check whether the lookup is complete, and pass a vector of handles to ```WaitAll``` to wait for completion. If any of the lookups fail, ```MultiGet``` will read the block from the SST file.

Another change in this PR is to rename ```SecondaryCacheHandle``` to ```SecondaryCacheResultHandle``` as it more accurately describes the return result of the secondary cache lookup, which is more like a future.

Tests:
1. Add unit tests in lru_cache_test
2. Benchmark results with no secondary cache configured
Master -
```
readrandom   :      41.175 micros/op 388562 ops/sec;  106.7 MB/s (7277999 of 7277999 found)
readrandom   :      41.217 micros/op 388160 ops/sec;  106.6 MB/s (7274999 of 7274999 found)
multireadrandom :      10.309 micros/op 1552082 ops/sec; (28908992 of 28908992 found)
multireadrandom :      10.321 micros/op 1550218 ops/sec; (29081984 of 29081984 found)
```

This PR -
```
readrandom   :      41.158 micros/op 388723 ops/sec;  106.8 MB/s (7290999 of 7290999 found)
readrandom   :      41.185 micros/op 388463 ops/sec;  106.7 MB/s (7287999 of 7287999 found)
multireadrandom :      10.277 micros/op 1556801 ops/sec; (29346944 of 29346944 found)
multireadrandom :      10.253 micros/op 1560539 ops/sec; (29274944 of 29274944 found)
```

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8405

Reviewed By: zhichao-cao

Differential Revision: D29190509

Pulled By: anand1976

fbshipit-source-id: 6f8eff6246712af8a297cfe22ea0d1c3b2a01bb0
2021-06-18 09:35:59 -07:00
Peter Dillinger
311a544c2a Use deleters to label cache entries and collect stats (#8297)
Summary:
This change gathers and publishes statistics about the
kinds of items in block cache. This is especially important for
profiling relative usage of cache by index vs. filter vs. data blocks.
It works by iterating over the cache during periodic stats dump
(InternalStats, stats_dump_period_sec) or on demand when
DB::Get(Map)Property(kBlockCacheEntryStats), except that for
efficiency and sharing among column families, saved data from
the last scan is used when the data is not considered too old.

The new information can be seen in info LOG, for example:

    Block cache LRUCache@0x7fca62229330 capacity: 95.37 MB collections: 8 last_copies: 0 last_secs: 0.00178 secs_since: 0
    Block cache entry stats(count,size,portion): DataBlock(7092,28.24 MB,29.6136%) FilterBlock(215,867.90 KB,0.888728%) FilterMetaBlock(2,5.31 KB,0.00544%) IndexBlock(217,180.11 KB,0.184432%) WriteBuffer(1,256.00 KB,0.262144%) Misc(1,0.00 KB,0%)

And also through DB::GetProperty and GetMapProperty (here using
ldb just for demonstration):

    $ ./ldb --db=/dev/shm/dbbench/ get_property rocksdb.block-cache-entry-stats
    rocksdb.block-cache-entry-stats.bytes.data-block: 0
    rocksdb.block-cache-entry-stats.bytes.deprecated-filter-block: 0
    rocksdb.block-cache-entry-stats.bytes.filter-block: 0
    rocksdb.block-cache-entry-stats.bytes.filter-meta-block: 0
    rocksdb.block-cache-entry-stats.bytes.index-block: 178992
    rocksdb.block-cache-entry-stats.bytes.misc: 0
    rocksdb.block-cache-entry-stats.bytes.other-block: 0
    rocksdb.block-cache-entry-stats.bytes.write-buffer: 0
    rocksdb.block-cache-entry-stats.capacity: 8388608
    rocksdb.block-cache-entry-stats.count.data-block: 0
    rocksdb.block-cache-entry-stats.count.deprecated-filter-block: 0
    rocksdb.block-cache-entry-stats.count.filter-block: 0
    rocksdb.block-cache-entry-stats.count.filter-meta-block: 0
    rocksdb.block-cache-entry-stats.count.index-block: 215
    rocksdb.block-cache-entry-stats.count.misc: 1
    rocksdb.block-cache-entry-stats.count.other-block: 0
    rocksdb.block-cache-entry-stats.count.write-buffer: 0
    rocksdb.block-cache-entry-stats.id: LRUCache@0x7f3636661290
    rocksdb.block-cache-entry-stats.percent.data-block: 0.000000
    rocksdb.block-cache-entry-stats.percent.deprecated-filter-block: 0.000000
    rocksdb.block-cache-entry-stats.percent.filter-block: 0.000000
    rocksdb.block-cache-entry-stats.percent.filter-meta-block: 0.000000
    rocksdb.block-cache-entry-stats.percent.index-block: 2.133751
    rocksdb.block-cache-entry-stats.percent.misc: 0.000000
    rocksdb.block-cache-entry-stats.percent.other-block: 0.000000
    rocksdb.block-cache-entry-stats.percent.write-buffer: 0.000000
    rocksdb.block-cache-entry-stats.secs_for_last_collection: 0.000052
    rocksdb.block-cache-entry-stats.secs_since_last_collection: 0

Solution detail - We need some way to flag what kind of blocks each
entry belongs to, preferably without changing the Cache API.
One of the complications is that Cache is a general interface that could
have other users that don't adhere to whichever convention we decide
on for keys and values. Or we would pay for an extra field in the Handle
that would only be used for this purpose.

This change uses a back-door approach, the deleter, to indicate the
"role" of a Cache entry (in addition to the value type, implicitly).
This has the added benefit of ensuring proper code origin whenever we
recognize a particular role for a cache entry; if the entry came from
some other part of the code, it will use an unrecognized deleter, which
we simply attribute to the "Misc" role.

An internal API makes for simple instantiation and automatic
registration of Cache deleters for a given value type and "role".

Another internal API, CacheEntryStatsCollector, solves the problem of
caching the results of a scan and sharing them, to ensure scans are
neither excessive nor redundant so as not to harm Cache performance.

Because code is added to BlocklikeTraits, it is pulled out of
block_based_table_reader.cc into its own file.

This is a reformulation of https://github.com/facebook/rocksdb/issues/8276, without the type checking option
(could still be added), and with actual stat gathering.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8297

Test Plan: manual testing with db_bench, and a couple of basic unit tests

Reviewed By: ltamasi

Differential Revision: D28488721

Pulled By: pdillinger

fbshipit-source-id: 472f524a9691b5afb107934be2d41d84f2b129fb
2021-05-19 16:51:13 -07:00
anand76
feb06e83b2 Initial support for secondary cache in LRUCache (#8271)
Summary:
Defined the abstract interface for a secondary cache in include/rocksdb/secondary_cache.h, and updated LRUCacheOptions to take a std::shared_ptr<SecondaryCache>. An item is initially inserted into the LRU (primary) cache. When it ages out and evicted from memory, its inserted into the secondary cache. On a LRU cache miss and successful lookup in the secondary cache, the item is promoted to the LRU cache. Only support synchronous lookup currently. The secondary cache would be used to implement a persistent (flash cache) or compressed cache.

Tests:
Results from cache_bench and db_bench don't show any regression due to these changes.

cache_bench results before and after this change -
Command
```./cache_bench -ops_per_thread=10000000 -threads=1```
Before
```Complete in 40.688 s; QPS = 245774```
```Complete in 40.486 s; QPS = 246996```
```Complete in 42.019 s; QPS = 237989```
After
```Complete in 40.672 s; QPS = 245869```
```Complete in 44.622 s; QPS = 224107```
```Complete in 42.445 s; QPS = 235599```

db_bench results before this change, and with this change + https://github.com/facebook/rocksdb/issues/8213 and https://github.com/facebook/rocksdb/issues/8191 -
Commands
```./db_bench  --benchmarks="fillseq,compact" -num=30000000 -key_size=32 -value_size=256 -use_direct_io_for_flush_and_compaction=true -db=/home/anand76/nvm_cache/db -partition_index_and_filters=true```

```./db_bench -db=/home/anand76/nvm_cache/db -use_existing_db=true -benchmarks=readrandom -num=30000000 -key_size=32 -value_size=256 -use_direct_reads=true -cache_size=1073741824 -cache_numshardbits=6 -cache_index_and_filter_blocks=true -read_random_exp_range=17 -statistics -partition_index_and_filters=true -threads=16 -duration=300```
Before
```
DB path: [/home/anand76/nvm_cache/db]
readrandom   :      80.702 micros/op 198104 ops/sec;   54.4 MB/s (3708999 of 3708999 found)
```
```
DB path: [/home/anand76/nvm_cache/db]
readrandom   :      87.124 micros/op 183625 ops/sec;   50.4 MB/s (3439999 of 3439999 found)
```
After
```
DB path: [/home/anand76/nvm_cache/db]
readrandom   :      77.653 micros/op 206025 ops/sec;   56.6 MB/s (3866999 of 3866999 found)
```
```
DB path: [/home/anand76/nvm_cache/db]
readrandom   :      84.962 micros/op 188299 ops/sec;   51.7 MB/s (3535999 of 3535999 found)
```

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8271

Reviewed By: zhichao-cao

Differential Revision: D28357511

Pulled By: anand1976

fbshipit-source-id: d1cfa236f00e649a18c53328be10a8062a4b6da2
2021-05-13 22:58:40 -07:00
Peter Dillinger
78a309bf86 New Cache API for gathering statistics (#8225)
Summary:
Adds a new Cache::ApplyToAllEntries API that we expect to use
(in follow-up PRs) for efficiently gathering block cache statistics.
Notable features vs. old ApplyToAllCacheEntries:

* Includes key and deleter (in addition to value and charge). We could
have passed in a Handle but then more virtual function calls would be
needed to get the "fields" of each entry. We expect to use the 'deleter'
to identify the origin of entries, perhaps even more.
* Heavily tuned to minimize latency impact on operating cache. It
does this by iterating over small sections of each cache shard while
cycling through the shards.
* Supports tuning roughly how many entries to operate on for each
lock acquire and release, to control the impact on the latency of other
operations without excessive lock acquire & release. The right balance
can depend on the cost of the callback. Good default seems to be
around 256.
* There should be no need to disable thread safety. (I would expect
uncontended locks to be sufficiently fast.)

I have enhanced cache_bench to validate this approach:

* Reports a histogram of ns per operation, so we can look at the
ditribution of times, not just throughput (average).
* Can add a thread for simulated "gather stats" which calls
ApplyToAllEntries at a specified interval. We also generate a histogram
of time to run ApplyToAllEntries.

To make the iteration over some entries of each shard work as cleanly as
possible, even with resize between next set of entries, I have
re-arranged which hash bits are used for sharding and which for indexing
within a shard.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8225

Test Plan:
A couple of unit tests are added, but primary validation is manual, as
the primary risk is to performance.

The primary validation is using cache_bench to ensure that neither
the minor hashing changes nor the simulated stats gathering
significantly impact QPS or latency distribution. Note that adding op
latency histogram seriously impacts the benchmark QPS, so for a
fair baseline, we need the cache_bench changes (except remove simulated
stat gathering to make it compile). In short, we don't see any
reproducible difference in ops/sec or op latency unless we are gathering
stats nearly continuously. Test uses 10GB block cache with
8KB values to be somewhat realistic in the number of items to iterate
over.

Baseline typical output:

```
Complete in 92.017 s; Rough parallel ops/sec = 869401
Thread ops/sec = 54662

Operation latency (ns):
Count: 80000000 Average: 11223.9494  StdDev: 29.61
Min: 0  Median: 7759.3973  Max: 9620500
Percentiles: P50: 7759.40 P75: 14190.73 P99: 46922.75 P99.9: 77509.84 P99.99: 217030.58
------------------------------------------------------
[       0,       1 ]       68   0.000%   0.000%
(    2900,    4400 ]       89   0.000%   0.000%
(    4400,    6600 ] 33630240  42.038%  42.038% ########
(    6600,    9900 ] 18129842  22.662%  64.700% #####
(    9900,   14000 ]  7877533   9.847%  74.547% ##
(   14000,   22000 ] 15193238  18.992%  93.539% ####
(   22000,   33000 ]  3037061   3.796%  97.335% #
(   33000,   50000 ]  1626316   2.033%  99.368%
(   50000,   75000 ]   421532   0.527%  99.895%
(   75000,  110000 ]    56910   0.071%  99.966%
(  110000,  170000 ]    16134   0.020%  99.986%
(  170000,  250000 ]     5166   0.006%  99.993%
(  250000,  380000 ]     3017   0.004%  99.996%
(  380000,  570000 ]     1337   0.002%  99.998%
(  570000,  860000 ]      805   0.001%  99.999%
(  860000, 1200000 ]      319   0.000% 100.000%
( 1200000, 1900000 ]      231   0.000% 100.000%
( 1900000, 2900000 ]      100   0.000% 100.000%
( 2900000, 4300000 ]       39   0.000% 100.000%
( 4300000, 6500000 ]       16   0.000% 100.000%
( 6500000, 9800000 ]        7   0.000% 100.000%
```

New, gather_stats=false. Median thread ops/sec of 5 runs:

```
Complete in 92.030 s; Rough parallel ops/sec = 869285
Thread ops/sec = 54458

Operation latency (ns):
Count: 80000000 Average: 11298.1027  StdDev: 42.18
Min: 0  Median: 7722.0822  Max: 6398720
Percentiles: P50: 7722.08 P75: 14294.68 P99: 47522.95 P99.9: 85292.16 P99.99: 228077.78
------------------------------------------------------
[       0,       1 ]      109   0.000%   0.000%
(    2900,    4400 ]      793   0.001%   0.001%
(    4400,    6600 ] 34054563  42.568%  42.569% #########
(    6600,    9900 ] 17482646  21.853%  64.423% ####
(    9900,   14000 ]  7908180   9.885%  74.308% ##
(   14000,   22000 ] 15032072  18.790%  93.098% ####
(   22000,   33000 ]  3237834   4.047%  97.145% #
(   33000,   50000 ]  1736882   2.171%  99.316%
(   50000,   75000 ]   446851   0.559%  99.875%
(   75000,  110000 ]    68251   0.085%  99.960%
(  110000,  170000 ]    18592   0.023%  99.983%
(  170000,  250000 ]     7200   0.009%  99.992%
(  250000,  380000 ]     3334   0.004%  99.997%
(  380000,  570000 ]     1393   0.002%  99.998%
(  570000,  860000 ]      700   0.001%  99.999%
(  860000, 1200000 ]      293   0.000% 100.000%
( 1200000, 1900000 ]      196   0.000% 100.000%
( 1900000, 2900000 ]       69   0.000% 100.000%
( 2900000, 4300000 ]       32   0.000% 100.000%
( 4300000, 6500000 ]       10   0.000% 100.000%
```

New, gather_stats=true, 1 second delay between scans. Scans take about
1 second here so it's spending about 50% time scanning. Still the effect on
ops/sec and latency seems to be in the noise. Median thread ops/sec of 5 runs:

```
Complete in 91.890 s; Rough parallel ops/sec = 870608
Thread ops/sec = 54551

Operation latency (ns):
Count: 80000000 Average: 11311.2629  StdDev: 45.28
Min: 0  Median: 7686.5458  Max: 10018340
Percentiles: P50: 7686.55 P75: 14481.95 P99: 47232.60 P99.9: 79230.18 P99.99: 232998.86
------------------------------------------------------
[       0,       1 ]       71   0.000%   0.000%
(    2900,    4400 ]      291   0.000%   0.000%
(    4400,    6600 ] 34492060  43.115%  43.116% #########
(    6600,    9900 ] 16727328  20.909%  64.025% ####
(    9900,   14000 ]  7845828   9.807%  73.832% ##
(   14000,   22000 ] 15510654  19.388%  93.220% ####
(   22000,   33000 ]  3216533   4.021%  97.241% #
(   33000,   50000 ]  1680859   2.101%  99.342%
(   50000,   75000 ]   439059   0.549%  99.891%
(   75000,  110000 ]    60540   0.076%  99.967%
(  110000,  170000 ]    14649   0.018%  99.985%
(  170000,  250000 ]     5242   0.007%  99.991%
(  250000,  380000 ]     3260   0.004%  99.995%
(  380000,  570000 ]     1599   0.002%  99.997%
(  570000,  860000 ]     1043   0.001%  99.999%
(  860000, 1200000 ]      471   0.001%  99.999%
( 1200000, 1900000 ]      275   0.000% 100.000%
( 1900000, 2900000 ]      143   0.000% 100.000%
( 2900000, 4300000 ]       60   0.000% 100.000%
( 4300000, 6500000 ]       27   0.000% 100.000%
( 6500000, 9800000 ]        7   0.000% 100.000%
( 9800000, 14000000 ]        1   0.000% 100.000%

Gather stats latency (us):
Count: 46 Average: 980387.5870  StdDev: 60911.18
Min: 879155  Median: 1033777.7778  Max: 1261431
Percentiles: P50: 1033777.78 P75: 1120666.67 P99: 1261431.00 P99.9: 1261431.00 P99.99: 1261431.00
------------------------------------------------------
(  860000, 1200000 ]       45  97.826%  97.826% ####################
( 1200000, 1900000 ]        1   2.174% 100.000%

Most recent cache entry stats:
Number of entries: 1295133
Total charge: 9.88 GB
Average key size: 23.4982
Average charge: 8.00 KB
Unique deleters: 3
```

Reviewed By: mrambacher

Differential Revision: D28295742

Pulled By: pdillinger

fbshipit-source-id: bbc4a552f91ba0fe10e5cc025c42cef5a81f2b95
2021-05-11 16:17:10 -07:00
storagezhang
d9be6556aa Include C++ standard library headers instead of C compatibility headers (#8068)
Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/8068

Reviewed By: zhichao-cao

Differential Revision: D27147685

Pulled By: riversand963

fbshipit-source-id: 5428b1c0142ecae17c977fba31a6d49b52983d1c
2021-03-19 12:09:47 -07:00
Yanqin Jin
394210f280 Remove unused includes (#7604)
Summary:
This is a PR generated **semi-automatically** by an internal tool to remove unused includes and `using` statements.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7604

Test Plan: make check

Reviewed By: ajkr

Differential Revision: D24579392

Pulled By: riversand963

fbshipit-source-id: c4bfa6c6b08da1de186690d37eb73d8fff45aecd
2020-10-28 23:22:27 -07:00
Peter Dillinger
249eff0f30 Stats for redundant insertions into block cache (#6681)
Summary:
Since read threads do not coordinate on loading data into block
cache, two threads between Lookup and Insert can end up loading and
inserting the same data. This is particularly concerning with
cache_index_and_filter_blocks since those are hot and more likely to
be race targets if ejected from (or not pre-populated in) the cache.

Particularly with moves toward disaggregated / network storage, the cost
of redundant retrieval might be high, and we should at least have some
hard statistics from which we can estimate impact.

Example with full filter thrashing "cliff":

    $ ./db_bench --benchmarks=fillrandom --num=15000000 --cache_index_and_filter_blocks -bloom_bits=10
    ...
    $ ./db_bench --db=/tmp/rocksdbtest-172704/dbbench --use_existing_db --benchmarks=readrandom,stats --num=200000 --cache_index_and_filter_blocks --cache_size=$((130 * 1024 * 1024)) --bloom_bits=10 --threads=16 -statistics 2>&1 | egrep '^rocksdb.block.cache.(.*add|.*redundant)' | grep -v compress | sort
    rocksdb.block.cache.add COUNT : 14181
    rocksdb.block.cache.add.failures COUNT : 0
    rocksdb.block.cache.add.redundant COUNT : 476
    rocksdb.block.cache.data.add COUNT : 12749
    rocksdb.block.cache.data.add.redundant COUNT : 18
    rocksdb.block.cache.filter.add COUNT : 1003
    rocksdb.block.cache.filter.add.redundant COUNT : 217
    rocksdb.block.cache.index.add COUNT : 429
    rocksdb.block.cache.index.add.redundant COUNT : 241
    $ ./db_bench --db=/tmp/rocksdbtest-172704/dbbench --use_existing_db --benchmarks=readrandom,stats --num=200000 --cache_index_and_filter_blocks --cache_size=$((120 * 1024 * 1024)) --bloom_bits=10 --threads=16 -statistics 2>&1 | egrep '^rocksdb.block.cache.(.*add|.*redundant)' | grep -v compress | sort
    rocksdb.block.cache.add COUNT : 1182223
    rocksdb.block.cache.add.failures COUNT : 0
    rocksdb.block.cache.add.redundant COUNT : 302728
    rocksdb.block.cache.data.add COUNT : 31425
    rocksdb.block.cache.data.add.redundant COUNT : 12
    rocksdb.block.cache.filter.add COUNT : 795455
    rocksdb.block.cache.filter.add.redundant COUNT : 130238
    rocksdb.block.cache.index.add COUNT : 355343
    rocksdb.block.cache.index.add.redundant COUNT : 172478
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6681

Test Plan: Some manual testing (above) and unit test covering key metrics is included

Reviewed By: ltamasi

Differential Revision: D21134113

Pulled By: pdillinger

fbshipit-source-id: c11497b5f00f4ffdfe919823904e52d0a1a91d87
2020-04-27 13:20:27 -07:00
Levi Tamasi
e6f86cfb36 Revert the recent cache deleter change (#6620)
Summary:
Revert "Use function objects as deleters in the block cache (https://github.com/facebook/rocksdb/issues/6545)"

    This reverts commit 6301dbe7a7.

    Revert "Call out the cache deleter related interface change in HISTORY.md (https://github.com/facebook/rocksdb/issues/6606)"

    This reverts commit 3a35542f86.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6620

Test Plan: `make check`

Reviewed By: zhichao-cao

Differential Revision: D20773311

Pulled By: ltamasi

fbshipit-source-id: 7637a761f718f323ef0e7da959462e8fb06e7a2b
2020-03-31 16:11:06 -07:00
Levi Tamasi
6301dbe7a7 Use function objects as deleters in the block cache (#6545)
Summary:
As the first step of reintroducing eviction statistics for the block
cache, the patch switches from using simple function pointers as deleters
to function objects implementing an interface. This will enable using
deleters that have state, like a smart pointer to the statistics object
that is to be updated when an entry is removed from the cache. For now,
the patch adds a deleter template class `SimpleDeleter`, which simply
casts the `value` pointer to its original type and calls `delete` or
`delete[]` on it as appropriate. Note: to prevent object lifecycle
issues, deleters must outlive the cache entries referring to them;
`SimpleDeleter` ensures this by using the ("leaky") Meyers singleton
pattern.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6545

Test Plan: `make asan_check`

Reviewed By: siying

Differential Revision: D20475823

Pulled By: ltamasi

fbshipit-source-id: fe354c33dd96d9bafc094605462352305449a22a
2020-03-26 16:19:58 -07:00
sdong
fdf882ded2 Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433)
Summary:
When dynamically linking two binaries together, different builds of RocksDB from two sources might cause errors. To provide a tool for user to solve the problem, the RocksDB namespace is changed to a flag which can be overridden in build time.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6433

Test Plan: Build release, all and jtest. Try to build with ROCKSDB_NAMESPACE with another flag.

Differential Revision: D19977691

fbshipit-source-id: aa7f2d0972e1c31d75339ac48478f34f6cfcfb3e
2020-02-20 12:09:57 -08:00
Maysam Yabandeh
9a87ae46fd Use total charge in MaintainPoolSize (#5813)
Summary:
https://github.com/facebook/rocksdb/issues/5797 charges the block cache with the total of user-provided charge plus the metadata charge. It had a bug where in MaintainPoolSize the user-provided charge was used instead of the total charge. The patch fixes that.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5813

Differential Revision: D17412783

Pulled By: maysamyabandeh

fbshipit-source-id: 45c0ac9f1e2233760db5ccd61399605cd74edc87
2019-09-17 00:16:13 -07:00
Maysam Yabandeh
638d239507 Charge block cache for cache internal usage (#5797)
Summary:
For our default block cache, each additional entry has extra memory overhead. It include LRUHandle (72 bytes currently) and the cache key (two varint64, file id and offset). The usage is not negligible. For example for block_size=4k, the overhead accounts for an extra 2% memory usage for the cache. The patch charging the cache for the extra usage, reducing untracked memory usage outside block cache. The feature is enabled by default and can be disabled by passing kDontChargeCacheMetadata to the cache constructor.
This PR builds up on https://github.com/facebook/rocksdb/issues/4258
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5797

Test Plan:
- Existing tests are updated to either disable the feature when the test has too much dependency on the old way of accounting the usage or increasing the cache capacity to account for the additional charge of metadata.
- The Usage tests in cache_test.cc are augmented to test the cache usage under kFullChargeCacheMetadata.

Differential Revision: D17396833

Pulled By: maysamyabandeh

fbshipit-source-id: 7684ccb9f8a40ca595e4f5efcdb03623afea0c6f
2019-09-16 15:26:21 -07:00
Eli Pozniansky
74fb7f0ba5 Cleaned up and simplified LRU cache implementation (#5579)
Summary:
The 'refs' field in LRUHandle now counts only external references, since anyway we already have the IN_CACHE flag. This simplifies reference accounting logic a bit. Also cleaned up few asserts code as well as the comments - to be more readable.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5579

Differential Revision: D16286747

Pulled By: elipoz

fbshipit-source-id: 7186d88f80f512ce584d0a303437494b5cbefd7f
2019-07-16 19:17:45 -07:00
Zhongyi Xie
d68f9f4580 simplify include directive involving inttypes (#5402)
Summary:
When using `PRIu64` type of printf specifier, current code base does the following:
```
#ifndef __STDC_FORMAT_MACROS
#define __STDC_FORMAT_MACROS
#endif
#include <inttypes.h>
```
However, this can be simplified to
```
#include <cinttypes>
```
as long as flag `-std=c++11` is used.
This should solve issues like https://github.com/facebook/rocksdb/issues/5159
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5402

Differential Revision: D15701195

Pulled By: miasantreble

fbshipit-source-id: 6dac0a05f52aadb55e9728038599d3d2e4b59d03
2019-06-06 13:56:07 -07:00
Levi Tamasi
34f8ac0c99 Make adaptivity of LRU cache mutexes configurable (#5054)
Summary:
The patch adds a new config option to LRUCacheOptions that enables
users to choose whether to use an adaptive mutex for the LRU block
cache (on platforms where adaptive mutexes are supported). The default
is true if RocksDB is compiled with -DROCKSDB_DEFAULT_TO_ADAPTIVE_MUTEX,
false otherwise.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5054

Differential Revision: D14542749

Pulled By: ltamasi

fbshipit-source-id: 0065715ab6cf91f10444b737fed8c8aee6a8a0d2
2019-03-20 12:33:44 -07:00
Yi Wu
05d9d82181 Revert "Move MemoryAllocator option from Cache to BlockBasedTableOpti… (#4697)
Summary:
…ons (#4676)"

This reverts commit b32d087dbb.

`MemoryAllocator` needs to be with `Cache`, since cache entry can
outlive DB and block based table. The cache needs to hold reference to
memory allocator when deleting cache entry.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4697

Differential Revision: D13133490

Pulled By: yiwu-arbug

fbshipit-source-id: 8ef7e8a51263bfd929f892fd062665ff4ce9ce5a
2018-11-21 11:29:57 -08:00
Yi Wu
b32d087dbb Move MemoryAllocator option from Cache to BlockBasedTableOptions (#4676)
Summary:
Per offline discussion with siying, `MemoryAllocator` and `Cache` should be decouple. The idea is that memory allocator handles memory allocation, while cache handle cache policy.

It is normal that external cache libraries pack couple the two components for better optimization. If we want to integrate with such library in the future, we can make a wrapper of the library implementing both `Cache` and `MemoryAllocator` interface.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4676

Differential Revision: D13047662

Pulled By: yiwu-arbug

fbshipit-source-id: cd42e246d80ab600b4de47d073f7d2db308ce6dd
2018-11-13 13:48:38 -08:00
Yi Wu
f560c8f5c8 s/CacheAllocator/MemoryAllocator/g (#4590)
Summary:
Rename the interface, as it is mean to be a generic interface for memory allocation.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4590

Differential Revision: D10866340

Pulled By: yiwu-arbug

fbshipit-source-id: 85cb753351a40cb856c046aeaa3f3b369eef3d16
2018-10-26 14:30:30 -07:00
Igor Canadi
1cf5deb8fd Introduce CacheAllocator, a custom allocator for cache blocks (#4437)
Summary:
This is a conceptually simple change, but it touches many files to
pass the allocator through function calls.

We introduce CacheAllocator, which can be used by clients to configure
custom allocator for cache blocks. Our motivation is to hook this up
with folly's `JemallocNodumpAllocator`
(f43ce6d686/folly/experimental/JemallocNodumpAllocator.h),
but there are many other possible use cases.

Additionally, this commit cleans up memory allocation in
`util/compression.h`, making sure that all allocations are wrapped in a
unique_ptr as soon as possible.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4437

Differential Revision: D10132814

Pulled By: yiwu-arbug

fbshipit-source-id: be1343a4b69f6048df127939fea9bbc96969f564
2018-10-02 17:24:58 -07:00
Yanqin Jin
26d67e357e Support group commits of version edits (#3944)
Summary:
This PR supports the group commit of multiple version edit entries corresponding to different column families. Column family drop/creation still cannot be grouped. This PR is a subset of [PR 3752](https://github.com/facebook/rocksdb/pull/3752).
Closes https://github.com/facebook/rocksdb/pull/3944

Differential Revision: D8432536

Pulled By: riversand963

fbshipit-source-id: 8f11bd05193b6c0d9272d82e44b676abfac113cb
2018-06-28 12:34:39 -07:00
Taewook Oh
b557499eee Suppress leak warning for clang(LLVM) asan (#4066)
Summary:
Instead of __SANITIZE_ADDRESS__ macro, LLVM uses __has_feature(address_sanitzer) to check if ASAN is enabled for the build. I tested it with MySQL sanitizer build that uses RocksDB as a submodule.
Closes https://github.com/facebook/rocksdb/pull/4066

Reviewed By: riversand963

Differential Revision: D8668941

Pulled By: taewookoh

fbshipit-source-id: af4d1da180c1470d257a228f431eebc61490bc36
2018-06-27 22:13:48 -07:00
Yi Wu
724855c7da Fix LRUCache missing null check on destruct
Summary:
Fix LRUCache missing null check on destruct. The check is needed if LRUCache::DisownData is called.
Closes https://github.com/facebook/rocksdb/pull/3920

Differential Revision: D8191631

Pulled By: yiwu-arbug

fbshipit-source-id: d5014f6e49b51692c18a25fb55ece935f5a023c4
2018-05-29 15:13:09 -07:00
Yi Wu
bc7e8d472e LRUCache midpoint insertion
Summary:
Implement midpoint insertion strategy where new blocks will be insert to the middle of LRU list, then move the head on the first hit in cache.
Closes https://github.com/facebook/rocksdb/pull/3877

Differential Revision: D8100895

Pulled By: yiwu-arbug

fbshipit-source-id: f4bd83cb8be469e5d02072cfc8bd66011391f3da
2018-05-24 15:57:33 -07:00
Yi Wu
7a99c04311 refactor constructor of LRUCacheShard
Summary:
Update LRUCacheShard constructor so that adding new params to it don't need to add extra SetXXX() methods.
Closes https://github.com/facebook/rocksdb/pull/3896

Differential Revision: D8128618

Pulled By: yiwu-arbug

fbshipit-source-id: 6afa715de1493a50de413678761a765e3af9b83b
2018-05-23 18:57:42 -07:00
Phani Shekhar Mantripragada
4b65cfc723 Support for block_cache num_shards and other config via option string.
Summary:
Problem: Option string accepts only cache_size as parameter for block_cache which is specified as "block_cache=1M".
It doesn't accept other parameters like num_shards etc.

Changes :
1) ParseBlockBasedTableOption in block_based_table_factory is edited to accept cache options in the format "block_cache=<cache_size>:<num_shard_bits>:<strict_capacity_limit>:<high_pri_pool_ratio>".
Options other than cache_size are optional to maintain backward compatibility. The changes are valid for block_cache_compressed as well.
For example, "block_cache=1M:6:true:0.5", "block_cache=1M:6:true", "block_cache=1M:6" and "block_cache=1M" are all valid option strings.

2) Corresponding unit tests are added.
Closes https://github.com/facebook/rocksdb/pull/3108

Differential Revision: D6420997

Pulled By: sagar0

fbshipit-source-id: cdea8b785688d2802907974af27225ccc1c0cd43
2017-11-28 10:48:53 -08:00
Prashant D
d9240b548c Fix coverity uninitialized fields warnings in lru_cache
Summary:
Coverity uninitialized member variable warnings in lru_cache
Closes https://github.com/facebook/rocksdb/pull/3082

Differential Revision: D6173062

Pulled By: sagar0

fbshipit-source-id: 7bcfc653457bd362d46045d06527838c9a6adad6
2017-10-27 11:26:43 -07:00
raistlin
ee2b1ec1e8 Fix unstable floating point exception
Summary:
Fix unstable floating point exception, tested on Windows, 64-bit build.
The problem appeared in `SetCapacity()` method at line

`high_pri_pool_capacity_ = capacity_ * high_pri_pool_ratio_;`

`high_pri_pool_ratio_` was not initialized at that moment, because
`SetHighPriorityPoolRatio()` is called after `SetCapacity()`. So,
`high_pri_pool_ratio_` contained garbage, which caused "Floating point
exception" sometimes.
Closes https://github.com/facebook/rocksdb/pull/3052

Differential Revision: D6111161

Pulled By: yiwu-arbug

fbshipit-source-id: d170329111ad12b4bf9bbcf37bcb6411523438ae
2017-10-20 10:12:49 -07:00
Dmitri Smirnov
0ec90a7cc2 Add -DPORTABLE=1 to MSVC CI build
Summary:
Add -DPORTABLE=1
  port::cacheline_aligned_alloc() has arguments swapped which prevents every single test from running.
Closes https://github.com/facebook/rocksdb/pull/2815

Differential Revision: D5751661

Pulled By: siying

fbshipit-source-id: e0857d6e138ec46035b3c23d7c3c751901a0a4a0
2017-08-31 16:42:48 -07:00
Yi Wu
e83d6a02e3 Not using aligned_alloc with gcc4 + asan
Summary:
GCC < 5 + ASAN does not instrument aligned_alloc, which can make ASAN
report false-positive with "free on address which was not malloc" error.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61693

Also suppress leak warning with LRUCache::DisownData().
Closes https://github.com/facebook/rocksdb/pull/2783

Differential Revision: D5696465

Pulled By: yiwu-arbug

fbshipit-source-id: 87c607c002511fa089b18cc35e24909bee0e74b4
2017-08-29 21:56:02 -07:00
Archit Mishra
09ac6206ab Circumvent ASAN false positive
Summary:
Changes:
* checks if ASAN mode is on, and uses malloc and free in the constructor and destructor
Closes https://github.com/facebook/rocksdb/pull/2767

Differential Revision: D5671243

Pulled By: armishra

fbshipit-source-id: 8e4ad0f7f163400c4effa8617d3b30134119d802
2017-08-21 12:10:43 -07:00
yiwu-arbug
e367774d19 Overload new[] to properly align LRUCacheShard
Summary:
Also verify it fixes gcc7 compile failure #2672 (see also #2699)
Closes https://github.com/facebook/rocksdb/pull/2732

Differential Revision: D5620348

Pulled By: yiwu-arbug

fbshipit-source-id: 87db657ab734f23b1bfaaa9db9b9956d10eaef59
2017-08-14 14:41:56 -07:00
Daniel Black
16e0388205 LRUCacheShard cache line size alignment
Summary:
combining #2568 and #2612.
Closes https://github.com/facebook/rocksdb/pull/2620

Differential Revision: D5464394

Pulled By: IslamAbdelRahman

fbshipit-source-id: 9f71d3058dd6adaf02ce3b2de3a81a1228009778
2017-07-24 10:54:37 -07:00
Sushma Devendrappa
0655b58582 enable PinnableSlice for RowCache
Summary:
This patch enables using PinnableSlice for RowCache, changes include
not releasing the cache handle immediately after lookup in TableCache::Get, instead pass a Cleanble function which does Cache::RleaseHandle.
Closes https://github.com/facebook/rocksdb/pull/2492

Differential Revision: D5316216

Pulled By: maysamyabandeh

fbshipit-source-id: d2a684bd7e4ba73772f762e58a82b5f4fbd5d362
2017-07-17 15:08:30 -07:00
Siying Dong
3c327ac2d0 Change RocksDB License
Summary: Closes https://github.com/facebook/rocksdb/pull/2589

Differential Revision: D5431502

Pulled By: siying

fbshipit-source-id: 8ebf8c87883daa9daa54b2303d11ce01ab1f6f75
2017-07-15 16:11:23 -07:00
Siying Dong
d616ebea23 Add GPLv2 as an alternative license.
Summary: Closes https://github.com/facebook/rocksdb/pull/2226

Differential Revision: D4967547

Pulled By: siying

fbshipit-source-id: dd3b58ae1e7a106ab6bb6f37ab5c88575b125ab4
2017-04-27 18:06:12 -07:00
Maysam Yabandeh
4c9447d889 Add erase option to release cache
Summary:
This is useful when we put the entries in the block cache for accounting
purposes and do not expect it to be used after it is released. If the cache does not
erase the item in such cases not only the performance of cache is
negatively affected but the item's destructor not being called at the
time of release might violate the assumptions about the lifetime of the
object.

The new change adds a force_erase option to the Release method and
returns a boolean to indicate whehter the item is successfully deleted.
Closes https://github.com/facebook/rocksdb/pull/2180

Differential Revision: D4916032

Pulled By: maysamyabandeh

fbshipit-source-id: 94409a346069923cac9de8e57adc313b4ed46f28
2017-04-24 11:28:36 -07:00
Siying Dong
d2dce5611a Move some files under util/ to separate dirs
Summary:
Move some files under util/ to new directories env/, monitoring/ options/ and cache/
Closes https://github.com/facebook/rocksdb/pull/2090

Differential Revision: D4833681

Pulled By: siying

fbshipit-source-id: 2fd8bef
2017-04-05 19:09:16 -07:00