This is beneficial when iterators are reused and seeks are not random
but increasing. It is additionally beneficial with larger block sizes and keys with common prefixes.
Add a benchmark "seekordered" to db_bench that reuses iterators across
increasing seeks. Add support to the benchmark to count comparisons made and to support common key prefix length. Change benchmark random seeds to be reproducible for entire benchmark suite executions but unique for threads in different benchmarks runs. This changes a benchmark suite of readrandom,seekrandom from having a 100% found ratio as previously it had the same seed used for fillrandom.
./db_bench --benchmarks=fillrandom,compact,seekordered --block_size=262144 --comparisons=1 --key_prefix=100
without this change (though with benchmark changes):
seekrandom : 55.309 micros/op; (631820 of 1000000 found)
Comparisons: 27001049
seekordered : 1.732 micros/op; (631882 of 1000000 found)
Comparisons: 26998402
with this change:
seekrandom : 55.866 micros/op; (631820 of 1000000 found)
Comparisons: 26952143
seekordered : 1.686 micros/op; (631882 of 1000000 found)
Comparisons: 25549369
For ordered seeking, this is a reduction of 5% comparisons and a 3% speedup. For random seeking (with single use iterators) the comparisons and speed are less than 1% and likely noise.
PiperOrigin-RevId: 351149832
Clang 10 includes the optimizations described in
https://bugs.llvm.org/show_bug.cgi?id=41761. This means that the
platform-independent implementations of {Decode,Encode}Fixed{32,64}()
compile to one instruction on the most recent Clang and GCC.
PiperOrigin-RevId: 306330166
leveldb::Env::DeleteFile was replaced with leveldb::Env::RemoveFile in
all tests. This allows us to remove workarounds for windows.h #defining
DeleteFile.
PiperOrigin-RevId: 289121105
The "DeleteFile" method name causes pain for Windows developers, because
<windows.h> #defines a DeleteFile macro to DeleteFileW or DeleteFileA.
Current code uses workarounds, like #undefining DeleteFile everywhere an
Env is declared, implemented, or used.
This CL removes the need for workarounds by renaming Env::DeleteFile to
Env::RemoveFile. For consistency, Env::DeleteDir is also renamed to
Env::RemoveDir. A few internal methods are also renamed for consistency.
Software that supports Windows is expected to migrate any Env
implementations and usage to Remove{File,Dir}, and never use the name
Env::Delete{File,Dir} in its code.
The renaming is done in a backwards-compatible way, at the risk of
making it slightly more difficult to build a new correct Env
implementation. The backwards compatibility is achieved using the
following hacks:
1) Env::Remove{File,Dir} methods are added, with a default
implementation that calls into Env::Delete{File,Dir}. This makes old
Env implementations compatible with code that calls into the updated
API.
2) The Env::Delete{File,Dir} methods are no longer pure virtuals.
Instead, they gain a default implementation that calls into
Env::Remove{File,Dir}. This makes updated Env implementations
compatible with code that calls into the old API.
The cost of this approach is that it's possible to write an Env without
overriding either Rename{File,Dir} or Delete{File,Dir}, without getting
a compiler warning. However, attempting to run the test suite will
immediately fail with an infinite call stack ending in
{Remove,Delete}{File,Dir}, making developers aware of the problem.
PiperOrigin-RevId: 288710907
Using CMAKE_INSTALL_INCLUDEDIR before including GNUINstallDirs results
in a broken installation when CMAKE_INSTALL_PREFIX is a non-standard
directory.
Inspired from https://github.com/google/crc32c/pull/39
PiperOrigin-RevId: 278427974
Added unreached return at the end of Version::Get::State::Match
to stop this _incorrect_ warning:
version_set.cc:376:5: warning: control reaches end of
non-void function [-Wreturn-type]
This warning was being emitted when building with clang 6.0.1-10
and also emitted by lgtm.com when statically analyzing leveldb even
though all SaverState enumeration values were handled.
PiperOrigin-RevId: 272455474
Previously used check_cxx_source_compiles to attempt a
build to determine support for clang thread safety checks.
This change is to support static analysis of the leveldb source by
lgtm.com (using Semmle). It failed to build with the following error:
```
[2019-07-04 22:29:58] [build] c++: error: unrecognized command line option ‘-Wthread-safety’; did you mean ‘-fthread-jumps’?
[2019-07-04 22:30:02] [build] make[2]: *** [CMakeFiles/leveldb.dir/build.make:66: CMakeFiles/leveldb.dir/db/builder.cc.o] Error 1
```
PiperOrigin-RevId: 272275528
A recent change (4cb80b7ddce6f) to DBImpl::DeleteObsoleteFiles
unlocked DBImpl::mutex_ while deleting files to allow for
greater concurrency. This change improves on the prior in
a few areas:
1. The table is evicted from the table cache before unlocking
the mutex. This should only improve performance.
2. This implementation is slightly simpler, but at the cost of
a bit more memory usage.
3. A comment adding more detail as to why the mutex is being
unlocked and why it is safe to do so.
PiperOrigin-RevId: 253111645
mutex_ was already acquired before accessing DBImpl::versions_ in all
but one place: DBImpl::GetApproximateSizes. This change requires mutex_
to be held before accessing versions_.
PiperOrigin-RevId: 248390814
The previous attempt of having EnvPosix use O_CLOEXEC (close-on-exec()) when opening file descriptors added tests that relied on procfs, which is Linux-specific. These tests failed on macOS. Unfortunately, the test failures were not caught due to a (since fixed) error in our Travis CI configuration.
This CL re-structures the tests to only rely on POSIX features. Since there is no POSIX-compliant way to get a file name/path out of a file descriptor, this CL breaks up the O_CLOEXEC test into multiple tests, where each Env method that creates an FD gets its own test. This is intended to make it easier to find and fix errors in Env implementations.
This CL also fixes the implementation of NewLogger() to use O_CLOEXEC on macOS. The current implementation passes "we" to fopen(), but the macOS standard C library does not implement the "e" flag yet.
PiperOrigin-RevId: 247088953
Currently, the benchmark used to assess leveldb changes lives in db/. The codebase also contains two benchmarks against other database engines in doc/bench/. Moving all the benchmarks in one place opens up the way for extracting common code.
PiperOrigin-RevId: 246737541
1) Convert iterator-based for loops to C++11 foreach loops.
2) Convert "void operator=" to "T& operator=".
3) Switch from copy operators from private to public deleted.
4) Switch from empty ctors / dtors to "= default" where appropriate.
PiperOrigin-RevId: 246679195
Use clang-format to correct formatting to be in agreement with the [Google C++ Style Guide](https://google.github.io/styleguide/cppguide.html). Doing this simplifies the process of accepting changes. Also fixed a few warnings flagged by clang-tidy.
PiperOrigin-RevId: 246350737
