Memory compression and deduplication

Project description

Thanks to swapping FreeBSD can run processes even if it’s not possible to place new pages in memory. However, moving VM objects to and from secondary storage can be expensive. The goal of this project is to implement two features that will allow to remove duplicated pages and compress pages which can be well compressed. Both optimizations should increase VM performance and flash drives lifetime.

Approach to solving the problem

At the beginning the project will focus on memory deduplication. After this I might work on memory compression depending on time and needs.

Please note that this paragraph will be updated during my research.

There are three main problems in memory deduplication:

In this section I would like to answer above questions and present the idea behind my implementation.

Memory deduplication can improve VM performance in many cases. One of them is running multiple virtual machines with the same OS. From VM's perspective memory allocated by the virtual machines is unknown, i.e. it doesn't know anything about the source and content of pages, so it cannot know which pages could be the same.

We can periodically check which pages can be merged. VM already implements daemons for paging and swapping using SYSINIT(9) and they can be considered as good examples for memory deduplication.

Given two pages the daemon can merge them when:

During the project I will check the following approaches:

Deliverables

Milestones

Start

End

Task

May 25

May 31

Start of coding.

June 1

June 7

Create structures.

June 8

June 14

Deduplicate page table pages.

June 15

June 21

Deduplicate page table pages.

June 22

June 26

June 26 19:00 UTC

July 3 19:00 UTC

Mid-term Evaluations.

July 4

July 12

July 13

July 19

July 20

July 26

July 27

August 2

August 3

August 9

August 10

August 16

Code review.

August 17

August 21

End of coding (soft).

August 21 19:00 UTC

End of coding (hard).

Test Plan

The Code

Repository: https://reviews.freebsd.org/diffusion/DEFGSOC/

Project page in Phabricator: https://reviews.freebsd.org/project/profile/52/

SummerOfCode2015/MemoryCompressionDeduplication (last edited 2015-05-30 12:18:45 by KonradWitaszczyk)