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Improve documentation of the allow_os_buffer parameter.

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This commit is contained in:
Edouard Alligand 2016-03-16 15:37:55 +01:00
parent 5bd3da1c59
commit 3d29f91466
1 changed files with 17 additions and 1 deletions
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18
include/rocksdb/options.h
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@ -1041,7 +1041,23 @@ struct DBOptions {
// large amounts of data (such as xfs's allocsize option).
size_t manifest_preallocation_size;
// Data being read from file storage may be buffered in the OS
// Hint the OS that it should not buffer disk I/O. Enabling this
// parameter may improve performance but increases pressure on the
// system cache.
//
// The exact behavior of this parameter is platform dependent.
//
// On POSIX systems, after RocksDB reads data from disk it will
// mark the pages as "unneeded". The operating system may - or may not
// - evict these pages from memory, reducing pressure on the system
// cache. If the disk block is requested again this can result in
// additional disk I/O.
//
// On WINDOWS system, files will be opened in "unbuffered I/O" mode
// which means that data read from the disk will not be cached or
// bufferized. The hardware buffer of the devices may however still
// be used. Memory mapped files are not impacted by this parameter.
//
// Default: true
bool allow_os_buffer;