Add to HISTORY and minor loose ends from #9294, #9254 (#9386)

Summary:
Loose ends relate to mmap on 32-bit systems. (Testing is more
complicated when the feature was completely disabled on 32-bit.)

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9386

Test Plan: CI

Reviewed By: ajkr

Differential Revision: D33590715

Pulled By: pdillinger

fbshipit-source-id: f2637036a538a552200adee65b6765fce8cae27b

HISTORY.md

@@ -6,10 +6,12 @@
 * Made the Env class extend the Customizable class.  Implementations need to be registered with the ObjectRegistry and to implement a Name() method in order to be created via this method.
 * `Options::OldDefaults` is marked deprecated, as it is no longer maintained.
 * Add ObjectLibrary::AddFactory and ObjectLibrary::PatternEntry classes.  This method and associated class are the preferred mechanism for registering factories with the ObjectLibrary going forward.  The ObjectLibrary::Register method, which uses regular expressions and may be problematic, is deprecated and will be in a future release.
+* Changed `BlockBasedTableOptions::block_size` from `size_t` to `uint64_t`.
 * Added API warning against using `Iterator::Refresh()` together with `DB::DeleteRange()`, which are incompatible and have always risked causing the refreshed iterator to return incorrect results.
 
 ### Behavior Changes
 * `DB::DestroyColumnFamilyHandle()` will return Status::InvalidArgument() if called with `DB::DefaultColumnFamily()`.
+* On 32-bit platforms, mmap reads are no longer quietly disabled, just discouraged.
 
 ### New Features
 * Added `Options::DisableExtraChecks()` that can be used to improve peak write performance by disabling checks that should not be necessary in the absence of software logic errors or CPU+memory hardware errors. (Default options are slowly moving toward some performance overheads for extra correctness checking.)
@@ -22,6 +24,9 @@
 * Fixed a bug of Sync() and Fsync() not using `fcntl(F_FULLFSYNC)` on OS X and iOS.
 * Fixed a significant performance regression in version 6.26 when a prefix extractor is used on the read path (Seek, Get, MultiGet). (Excessive time was spent in SliceTransform::AsString().)
 
+### New Features
+* Added RocksJava support for MacOS universal binary (ARM+x86)
+
 ## 6.28.0 (2021-12-17)
 ### New Features
 * Introduced 'CommitWithTimestamp' as a new tag. Currently, there is no API for user to trigger a write with this tag to the WAL. This is part of the efforts to support write-commited transactions with user-defined timestamps.

env/io_posix.cc

@@ -558,7 +558,7 @@ PosixRandomAccessFile::PosixRandomAccessFile(
 #endif
 {
   assert(!options.use_direct_reads || !options.use_mmap_reads);
-  assert(!options.use_mmap_reads || sizeof(void*) < 8);
+  assert(!options.use_mmap_reads);
 }
 
 PosixRandomAccessFile::~PosixRandomAccessFile() { close(fd_); }

include/rocksdb/env.h

@@ -84,7 +84,8 @@ struct EnvOptions {
   // Construct from Options
   explicit EnvOptions(const DBOptions& options);
 
-  // If true, then use mmap to read data
+  // If true, then use mmap to read data.
+  // Not recommended for 32-bit OS.
   bool use_mmap_reads = false;
 
   // If true, then use mmap to write data

include/rocksdb/options.h

@@ -772,7 +772,9 @@ struct DBOptions {
   // large amounts of data (such as xfs's allocsize option).
   size_t manifest_preallocation_size = 4 * 1024 * 1024;
 
-  // Allow the OS to mmap file for reading sst tables. Default: false
+  // Allow the OS to mmap file for reading sst tables.
+  // Not recommended for 32-bit OS.
+  // Default: false
   bool allow_mmap_reads = false;
 
   // Allow the OS to mmap file for writing.

port/win/env_win.cc

@@ -297,9 +297,9 @@ IOStatus WinFileSystem::NewRandomAccessFile(
 
   UniqueCloseHandlePtr fileGuard(hFile, CloseHandleFunc);
 
-  // CAUTION! This will map the entire file into the process address space
+  // CAUTION! This will map the entire file into the process address space.
-  if (options.use_mmap_reads && sizeof(void*) >= 8) {
+  // Not recommended for 32-bit platforms.
-    // Use mmap when virtual address-space is plentiful.
+  if (options.use_mmap_reads) {
     uint64_t fileSize;
 
     s = GetFileSize(fname, IOOptions(), &fileSize, dbg);