Conflicts:
	db/db_impl.cc
	db/db_test.cc
	db/memtable.cc
	db/version_set.cc
	include/rocksdb/statistics.h

Summary: I'm not sure what's the purpose of encoding file number to a new buffer for looking up the table cache. It seems to be unnecessary to me. With this patch, we point the lookup key to the address of the int64 of the file number.

Test Plan: make all check

Reviewers: dhruba, haobo, igor, kailiu

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14811

Summary:
In some places we have NotFound status created with empty message, but it doesn't avoid a malloc. With this patch, the malloc is avoided for that case.

The motivation of it is that I found in db_bench readrandom test when all keys are not existing, about 4% of the total running time is spent on malloc of Status, plus a similar amount of CPU spent on free of them, which is not necessary.

Test Plan: make all check

Reviewers: dhruba, haobo, igor

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14691

Summary:
A vector that leverages pre-allocated stack-based array to achieve better
performance for array with small amount of items.

Test Plan:
Added tests for both correctness and performance

Here is the performance benchmark between vector and autovector

Please note that in the test "Creation and Insertion Test", the test case were designed with the motivation described below:

* no element inserted: internal array of std::vector may not really get
  initialize.
* one element inserted: internal array of std::vector must have
  initialized.
* kSize elements inserted. This shows the most time we'll spend if we
  keep everything in stack.
* 2 * kSize elements inserted. The internal vector of
  autovector must have been initialized.

Note: kSize is the capacity of autovector

  =====================================================
  Creation and Insertion Test
  =====================================================
  created 100000 vectors:
  	each was inserted with 0 elements
  	total time elapsed: 128000 (ns)
  created 100000 autovectors:
  	each was inserted with 0 elements
  	total time elapsed: 3641000 (ns)
  created 100000 VectorWithReserveSizes:
  	each was inserted with 0 elements
  	total time elapsed: 9896000 (ns)
  -----------------------------------
  created 100000 vectors:
  	each was inserted with 1 elements
  	total time elapsed: 11089000 (ns)
  created 100000 autovectors:
  	each was inserted with 1 elements
  	total time elapsed: 5008000 (ns)
  created 100000 VectorWithReserveSizes:
  	each was inserted with 1 elements
  	total time elapsed: 24271000 (ns)
  -----------------------------------
  created 100000 vectors:
  	each was inserted with 4 elements
  	total time elapsed: 39369000 (ns)
  created 100000 autovectors:
  	each was inserted with 4 elements
  	total time elapsed: 10121000 (ns)
  created 100000 VectorWithReserveSizes:
  	each was inserted with 4 elements
  	total time elapsed: 28473000 (ns)
  -----------------------------------
  created 100000 vectors:
  	each was inserted with 8 elements
  	total time elapsed: 75013000 (ns)
  created 100000 autovectors:
  	each was inserted with 8 elements
  	total time elapsed: 18237000 (ns)
  created 100000 VectorWithReserveSizes:
  	each was inserted with 8 elements
  	total time elapsed: 42464000 (ns)
  -----------------------------------
  created 100000 vectors:
  	each was inserted with 16 elements
  	total time elapsed: 102319000 (ns)
  created 100000 autovectors:
  	each was inserted with 16 elements
  	total time elapsed: 76724000 (ns)
  created 100000 VectorWithReserveSizes:
  	each was inserted with 16 elements
  	total time elapsed: 68285000 (ns)
  -----------------------------------
  =====================================================
  Sequence Access Test
  =====================================================
  performed 100000 sequence access against vector
  	size: 4
  	total time elapsed: 198000 (ns)
  performed 100000 sequence access against autovector
  	size: 4
  	total time elapsed: 306000 (ns)
  -----------------------------------
  performed 100000 sequence access against vector
  	size: 8
  	total time elapsed: 565000 (ns)
  performed 100000 sequence access against autovector
  	size: 8
  	total time elapsed: 512000 (ns)
  -----------------------------------
  performed 100000 sequence access against vector
  	size: 16
  	total time elapsed: 1076000 (ns)
  performed 100000 sequence access against autovector
  	size: 16
  	total time elapsed: 1070000 (ns)
  -----------------------------------

Reviewers: dhruba, haobo, sdong, chip

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14655

Only try to use fallocate if it's actually present on the system.

Summary:
Add a pointer to the engineering design discussion forum.

Test Plan:

Reviewers:

CC:

Task ID: #

Blame Rev:

Summary: The previous patch is wrong. rep_.resize(kHeader) just resets the header portion to zero, and should not cause a re-allocation if g++ does it right. I will go ahead and revert it.

Test Plan: make check

Reviewers: dhruba, sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14793

Summary: tmp_batch_ will get re-allocated for every merged write batch because of the existing resize in WriteBatch::Clear. Note that in DBImpl::BuildBatchGroup, we have a hard coded upper limit of batch size 1<<20 = 1MB already.

Test Plan: make check

Reviewers: dhruba, sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14787

Summary:
Some changes to PlainTable format:
(1) support variable key length
(2) use user defined slice transformer to extract prefixes
(3) Run some test cases against PlainTable in db_test and table_test

Test Plan: test db_test

Reviewers: haobo, kailiu

CC: dhruba, igor, leveldb, nkg-

Differential Revision: https://reviews.facebook.net/D14457

Summary:
Instead of locking and saving a DB state, we can cache a DB state and update it only when it changes. This change reduces lock contention and speeds up read operations on the DB.

Performance improvements are substantial, although there is some cost in no-read workloads. I ran the regression tests on my devserver and here are the numbers:

  overwrite                    56345  ->   63001
  fillseq                      193730 ->  185296
  readrandom                   771301 -> 1219803 (58% improvement!)
  readrandom_smallblockcache   677609 ->  862850
  readrandom_memtable_sst      710440 -> 1109223
  readrandom_fillunique_random 221589 ->  247869
  memtablefillrandom           105286 ->   92643
  memtablereadrandom           763033 -> 1288862

Test Plan:
make asan_check
I am also running db_stress

Reviewers: dhruba, haobo, sdong, kailiu

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14679

fix missing gflags library

Summary:
For some tests I want to cache the database prior to running other tests on the same invocation
of db_bench. The readtocache test ignores --threads and --reads so those can be used by other tests
and it will still do a full read of --num rows with one thread. It might be invoked like:
  db_bench --benchmarks=readtocache,readrandom --reads 100 --num 10000 --threads 8

Task ID: #

Blame Rev:

Test Plan:
run db_bench

Revert Plan:

Database Impact:

Memcache Impact:

Other Notes:

EImportant:

- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -

Reviewers: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14739

Summary:
db_test should be the first to execute because it finds the most bugs.

Also, when third parties report issues, we don't want ldb error message, we prefer to have db_test error message. For example, see thread: https://github.com/facebook/rocksdb/issues/25

Test Plan: make check

Reviewers: dhruba, haobo, kailiu

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14715

Remove utilities/.DS_Store file.

C bindings: add a bunch of the newer options

Summary: I realized that "D14409 Avoid sorting in Version::Get() by presorting them in VersionSet::Builder::SaveTo()" is not done in an optimized place. SaveTo() is usually inside mutex. Move it to Finalize(), which is called out of mutex.

Test Plan: make all check

Reviewers: dhruba, haobo, kailiu

Reviewed By: dhruba

CC: igor, leveldb

Differential Revision: https://reviews.facebook.net/D14607

Summary: It seems to be a decision tradeoff in current codes: we make a malloc for every Get() to reduce one malloc for a flush inside mutex. It takes about 5% of CPU time in readrandom tests. We might consider the tradeoff to be the other way around.

Test Plan: make all check

Reviewers: dhruba, haobo, igor

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14697

Summary: A bug to fix. IT's already fixed in D14457, but want to check it in sooner to unblock tests

Test Plan: plain_table_db_test

Reviewers: nkg-, haobo

Reviewed By: nkg-

CC: kailiu, leveldb

Differential Revision: https://reviews.facebook.net/D14673

Summary:
This is the last diff that adds the property block to plain table.
The format resembles that of the block-based table: https://github.com/facebook/rocksdb/wiki/Rocksdb-table-format

  [data block]
  [meta block 1: stats block]
  [meta block 2: future extended block]
  ...
  [meta block K: future extended block]  (we may add more meta blocks in the future)
  [metaindex block]
  [index block: we only have the placeholder here, we can add persistent index block in the future]
  [Footer: contains magic number, handle to metaindex block and index block]
  <end_of_file>

Test Plan: extended existing property block test.

Reviewers: haobo, sdong, dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14523

Summary:
By disassemble the function, we found that the atomic variables do invoke the `lock` that locks the memory bus.
As a tradeoff, we protect the GetUsage by mutex and leave usage_ as plain size_t.

Test Plan: passed `cache_test`

Reviewers: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14667

Summary: make release complains signed unsigned comparison.

Test Plan: make release

Reviewers: kailiu

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14661

Summary: This diff will help us to figure out the memory usage for the cache part.

Test Plan: added a new memory usage test for cache

Reviewers: haobo, sdong, dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14559

Summary:
PlainTable now has a bug of the ordering of indexes for the prefixes in the same bucket. I thought std::map guaranteed key order but it didn't, probably because I didn't use it properly. But seems to me that we don't need to make extra sorting as input prefixes are already sorted. Found by problem by running leaf4 against plain table. Replace the map with a vector. It should performs better too.

After the fix, leaf4 unit tests are passing.

Test Plan:
run plain_table_db_test
Also going to run db_test with plain table in the uncommitted branch.

Reviewers: haobo, kailiu

Reviewed By: haobo

CC: nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D14649

There are still warning in some other environment, just move that useless variable `argv_`

Summary:
I realized that manifest will get deleted by PurgeObsoleteFiles in DBImpl, but it is sill cleaner to delete
files before we restore the backup

Test Plan: backupable_db_test

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14619

Summary:
Adds these counters
{ WAL_FILE_SYNCED, "rocksdb.wal.synced" }
  number of writes that request a WAL sync
{ WAL_FILE_BYTES, "rocksdb.wal.bytes" },
  number of bytes written to the WAL
{ WRITE_DONE_BY_SELF, "rocksdb.write.self" },
  number of writes processed by the calling thread
{ WRITE_DONE_BY_OTHER, "rocksdb.write.other" },
  number of writes not processed by the calling thread. Instead these were
  processed by the current holder of the write lock
{ WRITE_WITH_WAL, "rocksdb.write.wal" },
  number of writes that request WAL logging
{ COMPACT_READ_BYTES, "rocksdb.compact.read.bytes" },
  number of bytes read during compaction
{ COMPACT_WRITE_BYTES, "rocksdb.compact.write.bytes" },
  number of bytes written during compaction

Per-interval stats output was updated with WAL stats and correct stats for universal compaction
including a correct value for write-amplification. It now looks like:
                               Compactions
Level  Files Size(MB) Score Time(sec)  Read(MB) Write(MB)    Rn(MB)  Rnp1(MB)  Wnew(MB) RW-Amplify Read(MB/s) Write(MB/s)      Rn     Rnp1     Wnp1     NewW    Count  Ln-stall Stall-cnt
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  0        7      464  46.4       281      3411      3875      3411         0      3875        2.1      12.1        13.8      621        0      240      240      628       0.0         0
Uptime(secs): 310.8 total, 2.0 interval
Writes cumulative: 9999999 total, 9999999 batches, 1.0 per batch, 1.22 ingest GB
WAL cumulative: 9999999 WAL writes, 9999999 WAL syncs, 1.00 writes per sync, 1.22 GB written
Compaction IO cumulative (GB): 1.22 new, 3.33 read, 3.78 write, 7.12 read+write
Compaction IO cumulative (MB/sec): 4.0 new, 11.0 read, 12.5 write, 23.4 read+write
Amplification cumulative: 4.1 write, 6.8 compaction
Writes interval: 100000 total, 100000 batches, 1.0 per batch, 12.5 ingest MB
WAL interval: 100000 WAL writes, 100000 WAL syncs, 1.00 writes per sync, 0.01 MB written
Compaction IO interval (MB): 12.49 new, 14.98 read, 21.50 write, 36.48 read+write
Compaction IO interval (MB/sec): 6.4 new, 7.6 read, 11.0 write, 18.6 read+write
Amplification interval: 101.7 write, 102.9 compaction
Stalls(secs): 142.924 level0_slowdown, 0.000 level0_numfiles, 0.805 memtable_compaction, 0.000 leveln_slowdown
Stalls(count): 132461 level0_slowdown, 0 level0_numfiles, 3 memtable_compaction, 0 leveln_slowdown

Task ID: #3329644, #3301695

Blame Rev:

Test Plan:
Revert Plan:

Database Impact:

Memcache Impact:

Other Notes:

EImportant:

- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -

Reviewers: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14583

Summary: To reduce mutex contention caused by DBImpl.NewInternalIterator(), in this function, move all the iteration creation works out of mutex, only leaving object ref and get.

Test Plan:
make all check
will run db_stress for a while too to make sure no problem.

Reviewers: haobo, dhruba, kailiu

Reviewed By: haobo

CC: igor, leveldb

Differential Revision: https://reviews.facebook.net/D14589

[RocksDB][Performance Branch]Iterator Cleanup method only tries to find obsolete files if it has the last reference to a version

Summary: When deconstructing an iterator, no need to check obsolete file if it doesn't hold last reference of any version.

Test Plan: make all check

Reviewers: haobo, igor, dhruba, kailiu

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14595

Summary: @MarkCallaghan's tests indicate that performance with 8k rows in memtable is much worse than empty memtable. I wanted to add a regression tests that measures this effect, so we could optimize it. However, current config shows 634461 QPS on my devbox. Mark, any idea why this is so much faster than your measurements?

Test Plan: Ran the regression test.

Reviewers: MarkCallaghan, dhruba, haobo

Reviewed By: MarkCallaghan

CC: leveldb, MarkCallaghan

Differential Revision: https://reviews.facebook.net/D14511

Summary: In get operations, merge_operands is only used in few cases. Lazily initialize it can reduce average latency in some cases

Test Plan: make all check

Reviewers: haobo, kailiu, dhruba

Reviewed By: haobo

CC: igor, nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D14415

Conflicts:
	db/db_impl.cc
	db/memtable.cc