Summary: similar to D52809 add option to exclude zero counters.
Test Plan:
[yiwu@dev4504.prn1 ~/rocksdb] ./iostats_context_test
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from IOStatsContextTest
[ RUN ] IOStatsContextTest.ToString
[ OK ] IOStatsContextTest.ToString (0 ms)
[----------] 1 test from IOStatsContextTest (0 ms total)
[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (0 ms total)
[ PASSED ] 1 test.
Reviewers: anthony, yhchiang, andrewkr, IslamAbdelRahman, kradhakrishnan, sdong
Reviewed By: sdong
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D54591
Summary:
Users are confused on how to get the parallel compilation going. This
can help wire the parallelism.
Test Plan: Run manually
Reviewers: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D53931
Summary:
as titled, this will prevent the error that was printed because
test_names was evaluated before db_test was built.
Test Plan:
verified below command works and no longer prints errors:
$ make release -j32
verified below command still finds the right tests:
$ make J=32 parallel_check
Reviewers: igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D54117
Summary: unit_481 is misspelt. Fixing it.
Test Plan: Running make commit_prereq
Reviewers: leveldb
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D53757
Summary:
db/c_test.c uses the functions in db/c.cc. If we have tags generated
for one but not the other, it's easy to make mistakes like updating a function
signature and missing a call site.
Test Plan:
$ make tags
in vim:
:cscope find s rocksdb_options_set_compression_options
...
3 325 db/c_test.c <<main>>
rocksdb_options_set_compression_options(options, -14, -1, 0);
Reviewers: sdong, yhchiang, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D53685
Summary:
Added make targets parallel_test and parallel_dbtest to run
tests in parallel. Each test is run 32 times in parallel. There is a
timeout to catch hangs. The test continues after a failure and reports
non-zero status on failure
Test Plan: Run the two make targets
Reviewers: anthony, yhchiang, IslamAbdelRahman, kradhakrishnan, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D53079
Summary: This patch provides a mechanism to run pre commit tests on the local
branch before committing. This can help prevent frequent build breaks.
The tests can be run in parallel by specifying the J=<..> environment
variable.
Test Plan: Run manually
Reviewers: sdong rven tec
CC: leveldb@
Task ID: #9689218
Blame Rev:
Summary:
Moved all the tests that verify property correctness into a separate
file. The goal is to reduce compile time and complexity of db_test. I didn't
add parallelism for db_properties_test, even though these tests were
parallelized in db_test, since the file is small enough that it won't matter.
Some of these moves may be controversial since it's hard to say whether the
test is "verifying property correctness," or "using properties to verify
rocksdb's correctness." I'm interested in any opinions.
Test Plan: ran db_properties_test, also waiting on "make commit-prereq -j32"
Reviewers: yhchiang, IslamAbdelRahman, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D52995
These simple changes are required to allow builds on ppc64[le] systems
consistent with X86. The Makefile now recognizes both ppc64 and ppc64le, and
in the absence of PORTABLE=1, the code will be built analogously to the X86
-march=native.
Note that although GCC supports -mcpu=native -mtune=native on POWER, it
doesn't work correctly on all systems. This is why we need to get the actual
machine model from the AUX vector.
Makefile adjust paths for solaris build
Makefile enable _GLIBCXX_USE_C99 so that std::to_string is available
db_compaction_test.cc Initialise a variable to avoid a compilation error
db_impl.cc Include <alloca.h>
db_test.cc Include <alloca.h>
Environment.java recognise solaris envrionment
options_bulder.cc Make log unambiguous
geodb_impl.cc Make log and floor unambiguous
Summary:
GTEST dont compile under clang when -Werror=missing-field-initializers is set
revert this change
Test Plan:
USE_CLANG=1 make check
make check
Reviewers: rven
Reviewed By: rven
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D52455
Summary:
myrocks seems to build rocksdb using
-Wmissing-field-initializers (and treats warnings as errors). This diff
adds that flag to the rocksdb build, and fixes the compilation failures
that result. I have not checked for any other differences in the build
flags for rocksdb build as part of myrocks.
Test Plan: make check
Reviewers: sdong, rven
Reviewed By: rven
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D52443
This is an Env implementation that mirrors all storage-related methods on
two different backend Env's and verifies that they return the same
results (return status and read results). This is useful for implementing
a new Env and verifying its correctness.
Signed-off-by: Sage Weil <sage@redhat.com>
Summary: Ldb and sst_dump are not included in shared library now. Add it.
Test Plan:
Build
make release
make shared_lib
Reviewers: igor, kradhakrishnan, rven, yhchiang, IslamAbdelRahman, anthony
Reviewed By: IslamAbdelRahman, anthony
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D51735
Summary:
This diff is 1/3 in a sequence that introduces a skip list optimized for
a key that is a freshly-allocated const char*. The diff is broken into
pieces to make it easier to review. This piece only introduces the new
type by copying the existing SkipList, with mechanical naming changes
and reformatting.
Test Plan: new unit test
Reviewers: igor, sdong
Reviewed By: sdong
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D51279
Summary: forward_iterator_bench is not stable enough for build. Remove it for now.
Test Plan: Build it with both of CLANG and non-CLANG and make sure it builds.
Reviewers: rven, kradhakrishnan, anthony, yhchiang, igor, IslamAbdelRahman
Reviewed By: igor, IslamAbdelRahman
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D50991
Summary:
In case rocksdb java package is built using make rocksdbjavastaticrelease, then
only those rocksdb binary built under the virtual environments is release build.
This patch fix this issue.
Test Plan:
PORTABLE=1 V=2 make rocksdbjavastaticrelease -j32
and make sure -O2 and -NDEBUG is included when compiling all source files.
Reviewers: sdong, anthony, IslamAbdelRahman, rven, kradhakrishnan, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D50895
Summary:
Under a tailing workload, there were increased block cache
misses when a memtable was flushed because we were rebuilding iterators
in that case since the version set changed. This was exacerbated in the
case of iterate_upper_bound, since file iterators which were over the
iterate_upper_bound would have been deleted and are now brought back as
part of the Rebuild, only to be deleted again. We now renew the iterators
and only build iterators for files which are added and delete file
iterators for files which are deleted.
Refer to https://reviews.facebook.net/D50463 for previous version
Test Plan: DBTestTailingIterator.TailingIteratorTrimSeekToNext
Reviewers: anthony, IslamAbdelRahman, igor, tnovak, yhchiang, sdong
Reviewed By: sdong
Subscribers: yhchiang, march, dhruba, leveldb, lovro
Differential Revision: https://reviews.facebook.net/D50679
Summary:
This patch adds OptionsUtil::LoadOptionsFromFile() and
OptionsUtil::LoadLatestOptionsFromDB(), which allow developers
to construct DBOptions and ColumnFamilyOptions from a RocksDB
options file. Note that most pointer-typed options such as
merge_operator will not be constructed.
With this API, developers no longer need to remember all the
options in order to reopen an existing rocksdb instance like
the following:
DBOptions db_options;
std::vector<std::string> cf_names;
std::vector<ColumnFamilyOptions> cf_opts;
// Load primitive-typed options from an existing DB
OptionsUtil::LoadLatestOptionsFromDB(
dbname, &db_options, &cf_names, &cf_opts);
// Initialize necessary pointer-typed options
cf_opts[0].merge_operator.reset(new MyMergeOperator());
...
// Construct the vector of ColumnFamilyDescriptor
std::vector<ColumnFamilyDescriptor> cf_descs;
for (size_t i = 0; i < cf_opts.size(); ++i) {
cf_descs.emplace_back(cf_names[i], cf_opts[i]);
}
// Open the DB
DB* db = nullptr;
std::vector<ColumnFamilyHandle*> cf_handles;
auto s = DB::Open(db_options, dbname, cf_descs,
&handles, &db);
Test Plan:
Augment existing tests in column_family_test
options_test
db_test
Reviewers: igor, IslamAbdelRahman, sdong, anthony
Reviewed By: anthony
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D49095
Summary:
This patch allows rocksdb to persist options into a file on
DB::Open, SetOptions, and Create / Drop ColumnFamily.
Options files are created under the same directory as the rocksdb
instance.
In addition, this patch also adds a fail_if_missing_options_file in DBOptions
that makes any function call return non-ok status when it is not able to
persist options properly.
// If true, then DB::Open / CreateColumnFamily / DropColumnFamily
// / SetOptions will fail if options file is not detected or properly
// persisted.
//
// DEFAULT: false
bool fail_if_missing_options_file;
Options file names are formatted as OPTIONS-<number>, and RocksDB
will always keep the latest two options files.
Test Plan:
Add options_file_test.
options_test
column_family_test
Reviewers: igor, IslamAbdelRahman, sdong, anthony
Reviewed By: anthony
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D48285
Summary:
Reverting c745f1d2c4 because it
was based on an incorrect understanding of the correct way to enable
TSAN tests (it assumes "make COMPILE_WITH_TSAN=1 check" but in fact only
"COMPILE_WITH_TSAN=1 make check" is supported).
Test Plan: COMPILE_WITH_TSAN=1 make check
Reviewers: kradhakrishnan
Reviewed By: kradhakrishnan
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D50445
Summary:
TSAN builds for gcc 4.9 need a PIC version of the libraries
taken from the fbcode platform. This is accomplished by assuming every
.a has a _pic.a sibling, and by fixing the third-party2 zlib build.
Test Plan: make COMPILE_WITH_TSAN=1 check
Reviewers: sdong, igor
Reviewed By: igor
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D50331
Summary:
This patch introduces utilities/memory, which currently includes
GetApproximateMemoryUsageByType that reports different types of
rocksdb memory usage given a list of input DBs.
The API also take care of the case where Cache could be shared
across multiple column families / multiple db instances.
Currently, it reports memory usage of memtable, table-readers
and cache.
Test Plan: utilities/memory/memory_test.cc
Reviewers: igor, anthony, IslamAbdelRahman, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D49257
Summary:
The goal of this diff is to create a simple stress test with focus on catching:
* bugs in compaction/flush processes, especially the ones that cause assertion errors
* bugs in the code that deletes obsolete files
There are two parts of the test:
* write_stress, a binary that writes to the database
* write_stress_runner.py, a script that invokes and kills write_stress
Here are some interesting parts of write_stress:
* Runs with very high concurrency of compactions and flushes (32 threads total) and tries to create a huge amount of small files
* The keys written to the database are not uniformly distributed -- there is a 3-character prefix that mutates occasionally (in prefix mutator thread), in such a way that the first character mutates slower than second, which mutates slower than third character. That way, the compaction stress tests some interesting compaction features like trivial moves and bottommost level calculation
* There is a thread that creates an iterator, holds it for couple of seconds and then iterates over all keys. This is supposed to test RocksDB's abilities to keep the files alive when there are references to them.
* Some writes trigger WAL sync. This is stress testing our WAL sync code.
* At the end of the run, we make sure that we didn't leak any of the sst files
write_stress_runner.py changes the mode in which we run write_stress and also kills and restarts it. There are some interesting characteristics:
* At the beginning we divide the full test runtime into smaller parts -- shorter runtimes (couple of seconds) and longer runtimes (100, 1000) seconds
* The first time we run write_stress, we destroy the old DB. Every next time during the test, we use the same DB.
* We can run in kill mode or clean-restart mode. Kill mode kills the write_stress violently.
* We can run in mode where delete_obsolete_files_with_fullscan is true or false
* We can run with low_open_files mode turned on or off. When it's turned on, we configure table cache to only hold a couple of files -- that way we need to reopen files every time we access them.
Another goal was to create a stress test without a lot of parameters. So tools/write_stress_runner.py should only take one parameter -- runtime_sec and it should figure out everything else on its own.
In a separate diff, I'll add this new test to our nightly legocastle runs.
Test Plan:
The goal of this test was to retroactively catch the following bugs: D33045, D48201, D46899, D42399. I failed to reproduce D48201, but all others have been caught!
When i reverted https://reviews.facebook.net/D33045:
./write_stress --runtime_sec=200 --low_open_files_mode=true
Iterator statuts not OK: IO error: /fast-rocksdb-tmp/rocksdb_test/write_stress/089166.sst: No such file or directory
When i reverted https://reviews.facebook.net/D42399:
python tools/write_stress_runner.py --runtime_sec=5000
Running write_stress, will kill after 5 seconds: ./write_stress --runtime_sec=-1
Running write_stress, will kill after 2 seconds: ./write_stress --runtime_sec=-1 --destroy_db=false --delete_obsolete_files_with_fullscan=true
Running write_stress, will kill after 7 seconds: ./write_stress --runtime_sec=-1 --destroy_db=false
Running write_stress, will kill after 5 seconds: ./write_stress --runtime_sec=-1 --destroy_db=false
Running write_stress, will kill after 8 seconds: ./write_stress --runtime_sec=-1 --destroy_db=false --low_open_files_mode=true
Write to DB failed: IO error: /fast-rocksdb-tmp/rocksdb_test/write_stress/019250.sst: No such file or directory
ERROR: write_stress died with exitcode=-6
When i reverted https://reviews.facebook.net/D46899:
python tools/write_stress_runner.py --runtime_sec=1000
runtime: 1000
Going to execute write stress for [3, 3, 100, 3, 2, 100, 1, 788]
Running write_stress for 3 seconds: ./write_stress --runtime_sec=3 --low_open_files_mode=true
Running write_stress for 3 seconds: ./write_stress --runtime_sec=3 --destroy_db=false --delete_obsolete_files_with_fullscan=true
Running write_stress, will kill after 100 seconds: ./write_stress --runtime_sec=-1 --destroy_db=false --delete_obsolete_files_with_fullscan=true
write_stress: db/db_impl.cc:2070: void rocksdb::DBImpl::MarkLogsSynced(uint64_t, bool, const rocksdb::Status&): Assertion `log.getting_synced' failed.
ERROR: write_stress died with exitcode=-6
Reviewers: IslamAbdelRahman, yhchiang, rven, kradhakrishnan, sdong, anthony
Reviewed By: anthony
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D49533
Summary: Use DEBUG_LEVEL=0 in make release and make clean
Test Plan:
make clean
make release -j32
Reviewers: MarkCallaghan, sdong, anthony, IslamAbdelRahman, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D49125
Summary:
merge tools/db_crashtest2.py into tools/db_crashtest.py
python tools/db_crashtest.py -h # show help message, ALL parameters can be overwrite by arguments
Example usages:
python tools/db_crashtest.py blackbox # run blackbox with default parameters
python tools/db_crashtest.py blackbox --simple
python tools/db_crashtest.py whitebox # run whitebox with default parameters
python tools/db_crashtest.py whitebox --simple
all default parameters are identical to previous version.
Test Plan: `make crash_test` and make sure it can run with expected parameters pased to db_stress.
Reviewers: igor, rven, anthony, IslamAbdelRahman, yhchiang, sdong
Reviewed By: sdong
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D48567
Summary:
In the current make file, DEBUG_LEVEL is forced to set to 1
instead of default to 1. This patch fix this issue.
Test Plan:
DEBUG_LEVEL=2 make db_bench -j32
DEBUG_LEVEL=0 make db_bench -j32
DEBUG_LEVEL=0 make release -j32
And see whether there's a warning pops up.
Reviewers: MarkCallaghan, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D48933
Summary: In MyRocks, it is sometimes important to get propeties only for the subset of the database. This diff implements the API in RocksDB.
Test Plan: ran the GetPropertiesOfTablesInRange
Reviewers: rven, sdong
Reviewed By: sdong
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D48651
Summary:
This diff exclude alot of tests in db_test that are not compiling / failing under ROCKSD_LITE
Test Plan:
OPT=-DROCKSDB_LITE make check -j64
make check -j64
Reviewers: yhchiang, igor, sdong
Reviewed By: sdong
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D48771
Summary: As part of cleaning up dependencies for tech debt week, we are moving ldb and sst_dump tools from util to tools, since they are tools.
Test Plan: make check
Reviewers: sdong
Reviewed By: sdong
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D48747
Summary: manual_compaction_test.cc incorrectly in util. Moved to db.
Test Plan: make check
Reviewers: sdong
Reviewed By: sdong
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D48687
1) There is no need to download and install the compression libraries twice
just to get access to their header files during the compile phase.
2) Ensure that the compression library headers files used during the
compile phase are the same ones used to build the static library that
is linked into the library.
Summary:
As part of tech debt week, we are cleaning up dependencies.
This diff moves db_test_util.[h,cc] from util to db directory.
Test Plan: make check
Reviewers: igor, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D48543
1) There is no need to download and install the compression libraries twice
just to get access to their header files during the compile phase.
2) Ensure that the compression library headers files used during the
compile phase are the same ones used to build the static library that
is linked into the library.
in the Java jar. Also build the linux libraries using the portable flag to fix a problem with
the linux32 build and improve the general portability of the RocksDB dynamic libraries.
==> linux32: util/crc32c.cc:318:39: error: ‘_mm_crc32_u64’ was not declared in this scope
Summary:
I see a lot of users compiling RocksDB with `make` or `make all` and then using those binaries in production. They end up running debug builds :(
This diff makes it harder for them:
1. I added an explicit warning to INSTALL.md
2. When you compile with `make all`, your resulting library will be librocksdb_debug.a
3. I also print out a warning when you compile in debug mode.
Hopefully should be enough :)
Test Plan: none
Reviewers: rven, yhchiang, kradhakrishnan, anthony, sdong, dhruba, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D48093
Summary: unity_test will compile db_test with unity.a instead of librocksdb.a. This will test both the compilation and some small amount of runtime.
Test Plan: This is a test :)
Reviewers: kradhakrishnan
Reviewed By: kradhakrishnan
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D48297
This commit adds two new targets to the Makefile: rocksdb.cc and rocksdb.h
These files, when combined with the c.h header, are a self-contained RocksDB
source distribution called an amalgamation. (The name comes from SQLite's, which
is similar in concept.)
The main benefit of an amalgamation is that it's very easy to drop into a
new project. It also compiles faster compared to compiling individual source
files and potentially gives the compiler more opportunity to make optimizations
since it can see all functions at once.
rocksdb.cc and rocksdb.h are generated by a new script, amalgamate.py.
A detailed description of how amalgamate.py works is in a comment at the top of
the file.
There are also some small changes to existing files to enable the amalgamation:
* Use quotes for includes in unity build
* Fix an old header inclusion in util/xfunc.cc
* Move some includes outside ifdef in util/env_hdfs.cc
* Separate out tool sources in Makefile so they won't be included in unity.cc
* Unity build now produces a static library
Closes#733
Summary: Our valgrind testing is buggy and cumbersome in terms of locating the
error. It originates from the fact we accumulate all output for the tests. It is
extremely hard to locate the point of error.
The communication between valgrind and the script is not sturdy. We are
experiencing bugs.
Simplifying to stop on first error.
Test Plan: Run manually
Reviewers: sdong igor
CC: leveldb@
Task ID: #6968635
Blame Rev:
Summary:
Fix hex2String performance issues by removing sscanf dependency.
Also fixed some edge case handling (odd length, bad input).
Test Plan: Created a test file which called old and new implementation, and validated results are the same. I'll paste results in the phabricator diff.
Reviewers: igor, rven, anthony, IslamAbdelRahman, kradhakrishnan, yhchiang, sdong
Reviewed By: sdong
Subscribers: thatsafunnyname, leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D46785
Summary:
This patch fixes#7460559. It introduces SingleDelete as a new database
operation. This operation can be used to delete keys that were never
overwritten (no put following another put of the same key). If an overwritten
key is single deleted the behavior is undefined. Single deletion of a
non-existent key has no effect but multiple consecutive single deletions are
not allowed (see limitations).
In contrast to the conventional Delete() operation, the deletion entry is
removed along with the value when the two are lined up in a compaction. Note:
The semantics are similar to @igor's prototype that allowed to have this
behavior on the granularity of a column family (
https://reviews.facebook.net/D42093 ). This new patch, however, is more
aggressive when it comes to removing tombstones: It removes the SingleDelete
together with the value whenever there is no snapshot between them while the
older patch only did this when the sequence number of the deletion was older
than the earliest snapshot.
Most of the complex additions are in the Compaction Iterator, all other changes
should be relatively straightforward. The patch also includes basic support for
single deletions in db_stress and db_bench.
Limitations:
- Not compatible with cuckoo hash tables
- Single deletions cannot be used in combination with merges and normal
deletions on the same key (other keys are not affected by this)
- Consecutive single deletions are currently not allowed (and older version of
this patch supported this so it could be resurrected if needed)
Test Plan: make all check
Reviewers: yhchiang, sdong, rven, anthony, yoshinorim, igor
Reviewed By: igor
Subscribers: maykov, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D43179
Summary:
When running `make rocksdbjava V=1`, it currently does
not print out the original command but something odd instead:
mkdir -p jl/db
This patch tries to fix this issue.
Test Plan: make rocksdbjava V=1
Reviewers: igor, sdong, IslamAbdelRahman, meyering
Reviewed By: meyering
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D47061
Summary: This patch fixed couple build issues of rocksdbjavastaticrelease.
Test Plan: make rocksdbjavastaticrelease
Reviewers: sdong, anthony, IslamAbdelRahman, igor
Reviewed By: igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D45915
My use case is to build the rocksdb static library and tools, and
ideally I'd like to not spend time building the shared library and other
targets that I won't use.
Summary:
Initial implementation of Pessimistic Transactions. This diff contains the api changes discussed in D38913. This diff is pretty large, so let me know if people would prefer to meet up to discuss it.
MyRocks folks: please take a look at the API in include/rocksdb/utilities/transaction[_db].h and let me know if you have any issues.
Also, you'll notice a couple of TODOs in the implementation of RollbackToSavePoint(). After chatting with Siying, I'm going to send out a separate diff for an alternate implementation of this feature that implements the rollback inside of WriteBatch/WriteBatchWithIndex. We can then decide which route is preferable.
Next, I'm planning on doing some perf testing and then integrating this diff into MongoRocks for further testing.
Test Plan: Unit tests, db_bench parallel testing.
Reviewers: igor, rven, sdong, yhchiang, yoshinorim
Reviewed By: sdong
Subscribers: hermanlee4, maykov, spetrunia, leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D40869
Yi Wu