Running Pharoon the GemStone VM - WordPress.com · Running Pharoon the GemStone VM James Foster VP...
37
Running Pharo on the GemStone VM James Foster VP of Finance & Operations, GemTalk Systems LLC ESUG 2017 – Maribor, Slovenia 4 September 2017
Transcript of Running Pharoon the GemStone VM - WordPress.com · Running Pharoon the GemStone VM James Foster VP...
Running Pharo on the GemStone VM
James FosterVP of Finance & Operations, GemTalk Systems LLC
ESUG 2017 – Maribor, Slovenia4 September 2017
Agenda
• GemStone/S Introduction• Replacing Base Class Libraries• Questions
2
Limitations of traditional Smalltalks• Object space (image) must fit in (virtual) RAM• Object space visible to one (single-threaded) VM• Sharing objects between VMs is difficult
– Convert to non-object format (binary, XML, SQL)– No built-in object identity for multiple exports
• Object state is lost when VM exits
3
Welcome to the magical world of GemStone
• Object space limited by disk, not RAM
• Object space shared across multiple VMs on multiple hosts
• Transactional persistence
• Image from http://www.flickr.com/photos/laffy4k/182219003/
• Creative Commons License http://creativecommons.org/licenses/by-sa/2.0/ 4
GemStone/S Architecture
5
Gem Types
• Linked Gem– Gem in application process space
• Remote Procedure Call (RPC) Gem– GCI library in application space– Gem has separate process
6
Application &GCI Library
Gem
OS Process
GemApplication & GCI Library TCP/IP
OS Process 1 OS Process 2
One-Machine Process Locations (Linked Gem)
7
Application & GCI Library Gem
StoneSPC
Repository
One-Machine Process Locations (RPC Gem)
8
Application & GCI Library
Gem
StoneSPC
Repository
NetLDI
Two-Machine Process Locations (Gem on Stone Host)
9
Application & GCI Library
Client Host
NETWORK
Gem
StoneSPC
Repository
Stone HostNetLDI
Two-Machine Process Locations (Gem Remote from Stone)
10
Application & GCI Library
Gem
Gem Host
Remote SPC
PageServer
NETWORK
NetLDIStone
SPC
Repository
Stone Host
Page Server
NetLDI
Three-Machine Process Locations
11
Application & GCI Library
Client Host
NETWORK
Gem
Gem Host
Remote SPC
PageServer
NETWORK
NetLDIStone
SPC
Repository
Stone Host
Page Server
NetLDI
Shared Page Cache
12
Agenda
• GemStone/S Introduction• Replacing Base Class Libraries• Questions
13
Replacing Base Class Libraries
• Smalltalk was intended to allow exploration• Portability
– ANSI– Grease
• Can we go to a lower level?
• One approach to learn more
14
Option 1: Complete Replacement
• Not possible in most Smalltalks– Creating methods requires code
• GemStone schema editing with Topaz– Build process starts with a few base classes– But no methods for any class (initially)
• Challenges– Difficult to debug (most tools are internal)– VM has knowledge of schema
15
Option 2: Parallel Class Hierarchy
• GemStone’s namespace model allows separate hierarchy
16
Pharo Global Lookup
17
Smalltalk(a SmalltalkImage)
a SystemDictionary a GlobalVariable(Association)
globals
a CompiledMethod
a Symbolkey
an Objectvalue
Image
GemStone/S Global Lookup
18
AllUsers(a UserProfileSet) a UserProfile
a SymbolList(Array)
Repository
a SymbolDictionary a SymbolAssociation
symbolList
a CompiledMethod
a Symbolkey
an Objectvalue
Unique or Shared SymbolDictionary Instances
19
AllUsers
Bob
a SymbolList
Repository
1. UserGlobalsCarol
a SymbolList
2. Globals
1. UserGlobals
3. Published
SymbolDictionary instances
Unique or Shared SymbolAssociation Instances
20
1. UserGlobals
assoc
#Arraykey
Arrayvalue
2. Globals
1. UserGlobals
assockey
value
Bob’s SymbolList Carol’s SymbolList
Unique Keys
21
1. UserGlobals
assoc
#Arraykey
Arrayvalue
2. Globals
1. UserGlobals
assockey
value
Bob’s SymbolList Carol’s SymbolList
#List
Unique Values
22
1. UserGlobals
2. Globals
1. UserGlobals
Bob’s SymbolList Carol’s SymbolList
assoc
#OrderedCollectionkey
OrderedCollectionvalue
assoc
key
OrderedCollectionvalue
Problems with Parallel Class Hierarchy
• GemStone’s namespace model allows separate hierarchy
• But complications exist:– Literals– Classes known to the VM
23
Complication: Literals (and their superclasses)
• Array: #()• BlockClosure: []• Boolean: true, false• ByteArray: #[1 2 3]• Character: $a• Float: 1.23• SmallInteger: 42• String: ‘Smalltalk’• Symbol: #Array• UndefinedObject: nil
24
Complication: Classes Known to the VM
• Behavior, Class, Metaclass• Exception, MessageNotUnderstood, ZeroDivide, …• Pragma• Process• ProcessorScheduler
• So, we need to use (some) base classes
25
Problem: Conflicting Implementations
• Array>>printOn:– Pharo
• #(1 2 3) printString '#(1 2 3)'
– GemStone• #(1 2 3) printString 'anArray( 1, 2, 3)'
26
Option 3: Parallel Methods in GemStone Classes
• Each GemStone class has a collection of MethodDictionary instances– Methods are compiled into an “environment”– Message sends to same environment (by default)
• Method environments:0 = GemStone/S (default)1 = Maglev (reserved for Ruby)2+ are for others
– We use 2 for Pharo
27
28
Array Array class
a MethodDictionary a MethodDictionary
Pharo Method Dictionaries
ArrayedCollection
ArrayedCollection class
a MethodDictionary a MethodDictionary
SequenceableCollection
SequenceableCollection class
a MethodDictionary a MethodDictionary
29
Array Array class
methoddicts
a MethodDict [0]
nil
a MethodDict [2]
methoddicts
a MethodDict [0]
nil
a MethodDict [2]
GemStone Method Dictionaries - 1Sequenceable
CollectionSequenceable
Collection class
methoddicts
a MethodDict [0]
nil
a MethodDict [2]
methoddicts
a MethodDict [0]
nil
a MethodDict [2]
30
Array Array class
methoddicts
a MethodDict [0]
nil
a MethodDict [2]
methoddicts
a MethodDict [0]
nil
a MethodDict [2]
GemStone Method Dictionaries - 2Sequenceable
CollectionSequenceable
Collection class
methoddicts
a MethodDict [0]
nil
a MethodDict [2]
methoddicts
a MethodDict [0]
nil
a MethodDict [2]
ArrayedCollection
ArrayedCollection class
methoddicts
a MethodDict [0]
nil
a MethodDict [2]
methoddicts
a MethodDict [0]
nil
a MethodDict [2]
Sample Messages• Implicit
– “in env 0” #(1 2 3) printString 'anArray( 1, 2, 3)'– “in env 2” #(1 2 3) printString '#(1 2 3)'
• Explicit– #(1 2 3) @env0:printString 'anArray( 1, 2, 3)'– #(1 2 3) @env2:printString '#(1 2 3)’
31
Array
methoddicts
a MethodDict [0]
nil
a MethodDict [2]
printOn: aStream“for GemStone”
printOn: aStream“for Pharo”
Problems with Using GemStone Classes
• GemStone class might have different schema– OrderedCollection in Pharo
• Instance variables: (array firstIndex lastIndex)
– OrderedCollection in GemStone• No instance variables
– Since OrderedCollection is not known to the compiler, we don’t have to use GemStone’s class
32
Options
1. Replace all classesBut schema is wrong in some casesAnd we would like to use tools during development
2. Use parallel classes exclusivelyBut compiler & VM know about some GemStone classes
3. Use parallel methods exclusivelyBut schema is different for some classes
4. HybridUse GemStone classes when necessary
Use parallel classes otherwiseUse method environment 2 for everything
33
Tools
• Topaz– GemStone’s command-line interface
• GemBuilder for Smalltalk (GBS)– GemStone’s GUI IDE for VA & VW
• Others– tODE– gt4gemstone– Jade
34
Issues
• Incomplete Class Types– GemStone has in-memory Ephemerons, but no
Weak references– No 32-bit objects
• GemStone compiler is in VM– Not as easy to experiment with new syntax
• Low-level objects may need extensive rewrite– BlockClosure, Process, ProcessorScheduler, etc.
35
Demo• http://files.pharo.org/get-files/60/pharo-minimal.zip• http://downloads.gemtalksystems.com/pub/GemStone64/3.4.0-Alpha4/• https://github.com/jgfoster/PharoGs/tree/james/james
36
Questions?
37
GemTalk Systems LLC15220 NW Greenbrier Pkwy., Suite 240
Beaverton, Oregon, 97006
Voice & Fax: +1 503 766 4714
James G. FosterVPofFinance&Operations
www.gemtalksystems.com
®
