f2f4c8072f
Summary: The pupose of this diff is to expose per user-call level precise timing of block read, so that we can answer questions like: a Get() costs me 100ms, is that somehow related to loading blocks from file system, or sth else? We will answer that with EXACTLY how many blocks have been read, how much time was spent on transfering the bytes from os, how much time was spent on checksum verification and how much time was spent on block decompression, just for that one Get. A nano second stopwatch was introduced to track time with higher precision. The cost/precision of the stopwatch is also measured in unit-test. On my dev box, retrieving one time instance costs about 30ns, on average. The deviation of timing results is good enough to track 100ns-1us level events. And the overhead could be safely ignored for 100us level events (10000 instances/s), for example, a viewstate thrift call. Test Plan: perf_context_test, also testing with viewstate shadow traffic. Reviewers: dhruba Reviewed By: dhruba CC: leveldb, xjin Differential Revision: https://reviews.facebook.net/D12351
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-Stuctured-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 for more explanation.
See doc/impl.html for a brief overview of the implementation.
The public interface is in include/*.h. 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/db.h
Main interface to the DB: Start here
include/options.h
Control over the behavior of an entire database, and also
control over the behavior of individual reads and writes.
include/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/iterator.h
Interface for iterating over data. You can get an iterator
from a DB object.
include/write_batch.h
Interface for atomically applying multiple updates to a database.
include/slice.h
A simple module for maintaining a pointer and a length into some
other byte array.
include/status.h
Status is returned from many of the public interfaces and is used
to report success and various kinds of errors.
include/env.h
Abstraction of the OS environment. A posix implementation of
this interface is in util/env_posix.cc
include/table_builder.h
Lower-level modules that most clients probably won't use directly
include/cache.h
An API for the block cache.
include/compaction_filter.h
An API for a application filter invoked on every compaction.
include/filter_policy.h
An API for configuring a bloom filter.
include/memtablerep.h
An API for implementing a memtable.
include/statistics.h
An API to retrieve various database statistics.
include/transaction_log_iterator.h
An API to retrieve transaction logs from a database.