Summary:
I was investigating performance issues in the SstFileWriter and found all of the following:
- The SstFileWriter::Add() function created a local InternalKey every time it was called generating a allocation and free each time. Changed to have an InternalKey member variable that can be reset with the new InternalKey::Set() function.
- In SstFileWriter::Add() the smallest_key and largest_key values were assigned the result of a ToString() call, but it is simpler to just assign them directly from the user's key.
- The Slice class had no move constructor so each time one was returned from a function a new one had to be allocated, the old data copied to the new, and the old one was freed. I added the move constructor which also required a copy constructor and assignment operator.
- The BlockBuilder::CurrentSizeEstimate() function calculates the current estimate size, but was being called 2 or 3 times for each key added. I changed the class to maintain a running estimate (equal to the original calculation) so that the function can return an already calculated value.
- The code in BlockBuilder::Add() that calculated the shared bytes between the last key and the new key duplicated what Slice::difference_offset does, so I replaced it with the standard function.
- BlockBuilder::Add() had code to copy just the changed portion into the last key value (and asserted that it now matched the new key). It is more efficient just to copy the whole new key over.
- Moved this same code up into the 'if (use_delta_encoding_)' since the last key value is only needed when delta encoding is on.
- FlushBlockBySizePolicy::BlockAlmostFull calculated a standard deviation value each time it was called, but this information would only change if block_size of block_size_deviation changed, so I created a member variable to hold the value to avoid the calculation each time.
- Each PutVarint??() function has a buffer and calls std::string::append(). Two or three calls in a row could share a buffer and a single call to std::string::append().
Some of these will be helpful outside of the SstFileWriter. I'm not 100% the addition of the move constructor is appropriate as I wonder why this wasn't done before - maybe because of compiler compatibility? I tried it on gcc 4.8 and 4.9.
Test Plan: The changes should not affect the results so the existing tests should all still work and no new tests were added. The value of the changes was seen by manually testing the SstFileWriter class through MyRocks and adding timing code to identify problem areas.
Reviewers: sdong, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D59607
Summary:
The current implementation find the first different byte and try to increment it, if it cannot it return the original key
we can improve this by keep going after the first different byte to find the first non 0xFF byte and increment it
After trying this patch on some logdevice sst files I see decrease in there index block size by 8.5%
Test Plan: existing tests and updated test
Reviewers: yhchiang, andrewkr, sdong
Reviewed By: sdong
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D56241
Summary:
This is needed so we can measure compression ratio improvements
achieved by D52287.
The property compares raw data size against the total file size for a given
level. If the level is empty it should return 0.0.
Test Plan: new unit test
Reviewers: IslamAbdelRahman, yhchiang, sdong
Reviewed By: sdong
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D56967
Summary:
There is a hardcoded constraint in our statistics collection that prevents reading properties from more than 20 SST files. This means our statistics will be very inaccurate for databases with > 20 files since additional files are just ignored. The purpose of constraining the number of files used is to bound the I/O performed during statistics collection, since these statistics need to be recomputed every time the database reopened.
However, this constraint doesn't take into account the case where option "max_open_files" is -1. In that case, all the file metadata has already been read, so MaybeInitializeFileMetaData() won't incur any I/O cost. so this diff gets rid of the 20-file constraint in case max_open_files == -1.
Test Plan:
write into unit test db/db_properties_test.cc - "ValidateSampleNumber".
We generate 20 files with 2 rows and 10 files with 1 row.
If max_open_files !=-1, the `rocksdb.estimate-num-keys` should be (10*1 + 10*2)/20 * 30 = 45. Otherwise, it should be the ground truth, 50.
{F1089153}
Reviewers: andrewkr
Reviewed By: andrewkr
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D56253
Summary: I realized I again is wrong about the naming convention. Let me change it to the correct one.
Test Plan: Run unit tests.
Reviewers: IslamAbdelRahman, kradhakrishnan, yhchiang, andrewkr
Reviewed By: andrewkr
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D55041
Summary: Add a DB Property "rocksdb.current_version_number" for users to monitor version changes and stale iterators.
Test Plan: Add a unit test.
Reviewers: andrewkr, yhchiang, kradhakrishnan, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D54927
Summary:
Before this diff, there were duplicated constants to refer to properties (user-
facing API had strings and InternalStats had an enum). I noticed these were
inconsistent in terms of which constants are provided, names of constants, and
documentation of constants. Overall it seemed annoying/error-prone to maintain
these duplicated constants.
So, this diff gets rid of InternalStats's constants and replaces them with a map
keyed on the user-facing constant. The value in that map contains a function
pointer to get the property value, so we don't need to do string matching while
holding db->mutex_. This approach has a side benefit of making many small
handler functions rather than a giant switch-statement.
Test Plan: db_properties_test passes, running "make commit-prereq -j32"
Reviewers: sdong, yhchiang, kradhakrishnan, IslamAbdelRahman, rven, anthony
Reviewed By: anthony
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D53253
Summary:
There were just these two properties that didn't have any named
constant.
Test Plan:
build and below test
$ ./db_properties_test --gtest_filter=DBPropertiesTest.NumImmutableMemTable
Reviewers: yhchiang, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D53103
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
Islam AbdelRahman