transcendent memory - oracle · 2011-08-11 · transcendent memory objectives: •utilize ram more...
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Transcendent Memory and Friends
(Not just for virtualization anymore!)
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
Dan Magenheimer,Oracle Corp.
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Transcendent Memory’s“Friends”
frontswap
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
cleancache
ephemeralpersistent
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Transcendent Memory Objectives:
• Utilize RAM more efficiently to obtain
--Lower capital costs in the data center
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
--Lower power utilization in the data center
--Less I/O resulting in better performanceon many workloads
(with negligible loss on other workloads)
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Motivation: Memory-inefficient
workloads
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
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More motivation:
The memory capacity wall
100
1000
# Core
GB DRAM
Capacity Wall
� Memory capacity per core drop ~30% every 2 years
1
10
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
Wall
http://isca09.cs.columbia.edu/pres/24.pptxSource: Disaggregated Memory for Expansion and Sharing in Blade Server
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
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More motivation: Energy Savings
“…several studies show the contribution of memory to the total cost and power consumption of future systems increasing
from its current value of about 25%...”
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Source: Disaggregated Memory Architectures for Blade Servers, Kevin Lim, Univ Michigan, PhD Thesis
Go
og
le D
ata
Ce
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Be
lgiu
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Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
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<Insert Picture Here>
Slide from: Linux kernel support to exploit phase change memory, Linux Symposium 2010, Youngwoo Park, EE KAIST
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Disaggregated memory concept
CPUsDIMM
DIMM
CPUsDIMM
DIMM
CPUsDIMM
DIMM
CPUsDIMM
DIMM
DIMM
DIMM
Exo
fab
ric
DIMM
DIMM
DIMM
DIMM
� Break CPU-memory co-location
Leverage fast, shared communication fabrics
Memory
blade
CPUsDIMM
CPUsDIMM
DIMM
Exo
fab
ricDIMM
8
http://isca09.cs.columbia.edu/pres/24.pptx
Source: Disaggregated Memory for Expansion and Sharing in Blade Server
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
![Page 9: Transcendent Memory - Oracle · 2011-08-11 · Transcendent Memory Objectives: •Utilize RAM more efficiently to obtain--Lower capital costs in the data centerTranscendent Memory](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f38e2935f08644a521da414/html5/thumbnails/9.jpg)
OS Memory “Demand”
• Operating systems
are memory hogs!OS
Transcendent Memory on Xen (Xen Summit 2009) - Dan Magenheimer
Memory constraint
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• Operating systems are
memory hogs!
If you give an
OS
OS Physical Memory Management
Transcendent Memory on Xen (Xen Summit 2009) - Dan Magenheimer
If you give an
operating system
more memory�..
New larger memory constraint
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• Operating systems are
memory hogs!
�it uses up any
My name is Linux and I
am a memory hog
OS Physical Memory Management
Transcendent Memory on Xen (Xen Summit 2009) - Dan Magenheimer
�it uses up any
memory you give it!
memory hog
Memory constraint
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OS Memory “Asceticism”
ASSUME that it is “a good thing” for the an OS
to use as little RAM as possible at any given moment
• motivation may be economic or power or virtualization or ???
SUPPOSE there is a mechanism for the OS to surrender RAM
that it doesn’t need at this moment, so it can “pursue goodness”
SUPPOSE there is a mechanism for the OS to ask for and obtain a
page (or more) of RAM when it needs more RAM than it currently has
THEN9 HOW does an OS decide
how much RAM it “needs”?as-cet-i-cism, n. 1. extreme self-denial and austerity; rigorous self-discipline andactive restraint; renunciation of material comforts so as to achieve a higher state
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
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Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
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Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
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Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
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Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
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• CAPACITY: “X” GB
• Can read or write to any byte.
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
any byte.
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• CAPACITY: “X” GB
• Can read or write to any byte. • CAPACITY: ?????
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
any byte. • CAPACITY: ?????“unknowable”and may changedynamically!
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• CAPACITY: known• USES:
-kernel memory
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
-kernel memory-user memory-DMA-etc
• ADDRESSABILITY:Read/write any byte
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• CAPACITY: known• USES:
-kernel memory
• CAPACITY-“unknowable”- dynamic
SO9
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
-kernel memory-user memory-DMA-etc
• ADDRESSABILITY:Read/write any byte
SO9kernel/CPU can’t address directly!
SO9Need “permission”to access and needto “follow rules”(even the kernel!)
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• CAPACITY: known• USES:
-kernel memory
• THE RULES1. “page”-at-a-time
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
-kernel memory-user memory-DMA-etc
• ADDRESSABILITY:Read/write any byte
1. “page”-at-a-time2. to put data here,
kernel MUST use a“put page call”
3. (more rules later)
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Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
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We have a page that contains:
And the kernel wants to
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
And the kernel wants to “preserve” Larry in Type B
memory.
Note: All images of Larry the Crocodile are copyright Stephan Pastis
From the “Pearls Before Swine” comic strip dist. by United Feature Syndicate, Inc.
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We have a page that contains:
And the kernel wants to “preserve”
may say NO to kernel!
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
And the kernel wants to “preserve” Larry into Type B memory9 but,
Kernel MUST ask permission and may get told NO!
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We have a page that contains:
And the kernel wants to “preserve”
may say NO to kernel!
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
And the kernel wants to “preserve” Larry into Type B memory.
The kernel has two choices9
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We have a page that contains:
And the kernel wants to “preserve”
may say NO to kernel!
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
And the kernel wants to “preserve” Larry into Type B memory.
Two choices9
1. DEFINITELY want Larry back(e.g. “dirty” page)
may commit to keeping the
page around,
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We have a page that contains:
And the kernel wants to “preserve”
may say NO to kernel!
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
And the kernel wants to “preserve” Larry into Type B memory.
Two choices9
1. DEFINITELY want Larry back
2. PROBABLY want Larry back(e.g. “clean” pages)
may commit to keeping the
page around, or may not!
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We have a page that contains:
Two choices9
1. DEFINITELY want Larry back
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
1. DEFINITELY want Larry back
2. PROBABLY want Larry back
tran-scend-ent, adj., � beyond
the range of normal perception
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We have a page that contains:
Two choices9
1. DEFINITELY want Larry back
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
1. DEFINITELY want Larry back
“PERSISTENT PUT”
2. PROBABLY want Larry back
“EPHEMERAL PUT”
eph-em-er-al, adj., � transitory, existing
only briefly, short-lived (i.e. NOT persistent)
tran-scend-ent, adj., � beyond
the range of normal perception
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“PUT”
“GET”
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
“FLUSH”
Core Transcendent Memory Operations
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“Normal” RAM addressing
• byte-addressable
• virtual address:
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
• virtual address: @fffff80001024580
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“Normal” RAM addressing
• byte-addressable
• virtual address:
Transcendent Memory
•object-oriented addressing
•object is a page
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
• virtual address: @fffff80001024580
•“handle” addresses a page
•kernel can (mostly) choosehandle when a page is “put”
•uses same handle to “get”
•must ensure handle is and remains unique
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?
Why bother??
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
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Why bother?? Because,
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
Because once behind the curtain, we can do
interestingthings,
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compress on put
decompress on get
Interesting thing #1: Zcache
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
“Zcache”(2.6.39 staging driver)
on get
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Ooooh…
Interesting thing #2:
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
Transparently movepre-compressed pages
across a high(??)-speedcoherent(?) interconnect
Ooooh… Larry gots lotsa elbow room over heer..
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Interesting thing #2A:
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
RAMster:“peer-to-peer” Transcendent Memory
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Ooooh… Larry gots lotsa elbow room over
Interesting thing #2B:
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
,maybe only one large “memory server” shared
by many machines?
room over heer..
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Interesting thing #3:
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
SSmem: Transcendent Memory as a “safe” access layer for SSD or NVRAM
e.g. as a “RAM extension” not I/O device
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virtual machines (aka “guests”)
hypervisor
Interesting thing #4:
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
future?
Tmem support:
• multiple guests
• compression
• deduplication
Tmem supported in Xen since 4.0 (2009)
hypervisor (aka “host”)
hypervisor RAM
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Impact on Linux Memory Management Subsystem??
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
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? ?
Memory pressure?So what’s a kernel to do?
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
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Cleancache (merged for 3.0)
A “third level” “victim” cache for
otherwise Cleancache patchset:
“ephemeral put”
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
otherwise reclaimed clean
page cache pages
(optionally load-balanced across
multiple “clients”)
Cleancache patchset:
• vfs hooks to put clean page cache pages, get them back, and maintain coherency
• per-filesystem opt-in hooks
• shim to zcache in 2.6.39
• shim to Xen tmem in 3.0
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Frontswap (target merge 3.2)
Temporary emergency FAST
Frontswap patchset:
• swap subsystem hooks to “put”
“persistent put”
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
emergency FAST swap page store
(optionally load-balanced across
multiple “clients”)
• swap subsystem hooks to “put” swap cache pages and “get” them back, and maintain coherency
• manages tracking data structures (1 bit/page)
• “partial swapoff”
• shim to zcache in 2.6.39
• shim to Xen tmem merged in 3.1
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Cleancache & Frontswap
Cleancache and
Zcache, RAMster, Xen
tmem all
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
Cleancache and frontswap patches are the only core changes necessary to support ALL of Transcendent Memory’s “friends”!!
tmem all implemented as “drivers”
(no additional core kernel
changes required)
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Questions?
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
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BACKUP SLIDESBACKUP SLIDES
Transcendent Memory and Friends: Not just for virtualization anymore! -- Linuxcon 2011 -- Dan Magenheimer
![Page 48: Transcendent Memory - Oracle · 2011-08-11 · Transcendent Memory Objectives: •Utilize RAM more efficiently to obtain--Lower capital costs in the data centerTranscendent Memory](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f38e2935f08644a521da414/html5/thumbnails/48.jpg)
Transcendent Memory in Linux(status Aug 2, 2011)
Xen non-
Xen
name of patchset Linux
version
N Y zcache 2.6.39 staging driver
Y Y cleancache 3.0 Linus decided!
Y N selfballooning 3.1
Y ? frontswap-selfshrinking 3.1Y ? frontswap-selfshrinking 3.1
Y Y frontswap 3.2? linux-next
? Y RAMster ? In development
Transcendent Memory Lightning Talk -- Xen Summit 2011 -- Dan Magenheimer