95dda37858
Summary: When a new version is created, we sort all the files at every level based on their size. This is necessary because we want to compact the largest file first. The sorting takes quite a bit of CPU. Moved the sorting code to be outside the mutex. Also, the earlier code was sorting files at all levels but we do not need to sort the highest-number level because those files are never the cause of any compaction. To reduce sorting costs, we sort only the first few files in each level because it is likely that those are the only files in that level that will be picked for compaction. At steady state, I have seen that this patch increase throughout from 1500 writes/sec to 1700 writes/sec at the end of a 72 hour run. The cpu saving by not sorting the last level was not distinctive in this test run because there were only 100K files in the highest numbered level. I expect the cpu saving to be significant when the number of files is much higher. This is mostly an early preview and not ready for rigorous review. With this patch, the writs/sec is now bottlenecked not by the sorting code but by GetOverlappingInputs. I am working on a patch to optimize GetOverlappingInputs. Test Plan: make check Reviewers: MarkCallaghan, heyongqiang Reviewed By: heyongqiang Differential Revision: https://reviews.facebook.net/D6411
leveldb: A key-value store
Authors: Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com)
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.h
include/table_builder.h
Lower-level modules that most clients probably won't use directly