1560bb913e
Summary:
Added an option for readrandom benchmark to run with tailing iterator instead of Get. Benefit of tailing iterator is that it doesn't require locking DB mutex on access.
I also have some results when running on my machine. The results highly depend on number of cache shards. With our current benchmark setting of 4 table cache shards and 6 block cache shards, I don't see much improvements of using tailing iterator. In that case, we're probably seeing cache mutex contention.
Here are the results for different number of shards
cache shards tailing iterator get
6 1.38M 1.16M
10 1.58M 1.15M
As soon as we get rid of cache mutex contention, we're seeing big improvements in using tailing iterator vs. ordinary get.
Test Plan: ran regression test
Reviewers: dhruba, haobo, ljin, kailiu, sding
Reviewed By: haobo
CC: tnovak
Differential Revision: https://reviews.facebook.net/D15867
rocksdb: A persistent key-value store for flash storage
Authors: * The Facebook Database Engineering Team
* Build on earlier work on leveldb by Sanjay Ghemawat
(sanjay@google.com) and Jeff Dean (jeff@google.com)
This code is a library that forms the core building block for a fast
key value server, especially suited for storing data on flash drives.
It has an Log-Structured-Merge-Database (LSM) design with flexible tradeoffs
between Write-Amplification-Factor(WAF), Read-Amplification-Factor (RAF)
and Space-Amplification-Factor(SAF). It has multi-threaded compactions,
making it specially suitable for storing multiple terabytes of data in a
single database.
The core of this code has been derived from open-source leveldb.
The code under this directory implements a system for maintaining a
persistent key/value store.
See doc/index.html and github wiki (https://github.com/facebook/rocksdb/wiki)
for more explanation.
The public interface is in include/*. Callers should not include or
rely on the details of any other header files in this package. Those
internal APIs may be changed without warning.
Guide to header files:
include/rocksdb/db.h
Main interface to the DB: Start here
include/rocksdb/options.h
Control over the behavior of an entire database, and also
control over the behavior of individual reads and writes.
include/rocksdb/comparator.h
Abstraction for user-specified comparison function. If you want
just bytewise comparison of keys, you can use the default comparator,
but clients can write their own comparator implementations if they
want custom ordering (e.g. to handle different character
encodings, etc.)
include/rocksdb/iterator.h
Interface for iterating over data. You can get an iterator
from a DB object.
include/rocksdb/write_batch.h
Interface for atomically applying multiple updates to a database.
include/rocksdb/slice.h
A simple module for maintaining a pointer and a length into some
other byte array.
include/rocksdb/status.h
Status is returned from many of the public interfaces and is used
to report success and various kinds of errors.
include/rocksdb/env.h
Abstraction of the OS environment. A posix implementation of
this interface is in util/env_posix.cc
include/rocksdb/table_builder.h
Lower-level modules that most clients probably won't use directly
include/rocksdb/cache.h
An API for the block cache.
include/rocksdb/compaction_filter.h
An API for a application filter invoked on every compaction.
include/rocksdb/filter_policy.h
An API for configuring a bloom filter.
include/rocksdb/memtablerep.h
An API for implementing a memtable.
include/rocksdb/statistics.h
An API to retrieve various database statistics.
include/rocksdb/transaction_log.h
An API to retrieve transaction logs from a database.
Design discussions are conducted in https://www.facebook.com/groups/rocksdb.dev/