Re: [Jikesrvm-core] MMTk Questions

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Hi Sowjanya=2C

There=27s another copy here http=3A//www=2Eresearch=2Eibm=2Ecom/ismm04/s=
lides/mmtk-tutorial=2Epdf=2C but I don=27t actually think it has the ste=
p-by-step=2E

Off the top of my head=2C the steps you need are=3A

- Add a write barrier=2C and a remembered set=2E
- Add a second TraceLocal class to perform a nursery trace=2E
- Add some logic to =27poll=27 to decide when to do a nursery collection=
 or a full-heap collection
- Modify MyGcCollector to handle both nursery and mature-space collectio=
n (in the actual generational collectors this is split between the =27ge=
n=27 package and the per-mature-space packages=2E

cheers

----- Original Message -----
From=3A 100ji =3Citz100ji=40gmail=2Ecom=3E
Date=3A Tuesday=2C July 3=2C 2007 6=3A07 pm
Subject=3A Re=3A =5BJikesrvm-core=5D MMTk Questions
To=3A Discussion of day-to-day development and design among JikesRVM cor=
e team members =3Cjikesrvm-core=40lists=2Esourceforge=2Enet=3E

=3E Hi Robin=2C
=3E =

=3E I tried to get that presentation (
=3E http=3A//jikesrvm=2Esourceforge=2Enet/info/talks/ISMM04-MMTk=2Epdf) =
=2E =

=3E But=2C it
=3E has been moved somewhere=2E Can you please send the presentation =

=3E to me
=3E off list=2E
=3E =

=3E Thanks=2E
=3E =

=3E On 7/3/07=2C Robin Garner =3Crobin=2Egarner=40anu=2Eedu=2Eau=3E wrot=
e=3A
=3E =3E Steve and Perry=27s original presentation is on
=3E =3E
=3E =3E http=3A//www=2Ejikesrvm=2Eorg/Presentations
=3E =3E
=3E =3E cheers
=3E =3E
=3E =3E 100ji wrote=3A
=3E =3E =3E Hi Robin=2C
=3E =3E =3E
=3E =3E =3E Thanks for the reply=2E=A0 I have gone through the tutorial =
and
=3E =3E =3E implemented part(1 and 2) of it=2E However=2C the one I am =

=3E looking at has
=3E =3E =3E the Generational collector as a TODO and I read the code to
=3E =3E =3E understand(vaguely) how to implement one=2E=A0 Is there a =

=3E document that
=3E =3E =3E explains implementing a generational collector too=3F
=3E =3E =3E
=3E =3E =3E Thanks in advance=2C
=3E =3E =3E -Sowji
=3E =3E =3E
=3E =3E =3E On 6/28/07=2C Robin Garner =3Crobin=2Egarner=40anu=2Eedu=2Ea=
u=3E wrote=3A
=3E =3E =3E=3E Hi Sowjanya=2C
=3E =3E =3E=3E
=3E =3E =3E=3E While Eliot is right in that the MMTk tutorial is out of =

=3E date in its
=3E =3E =3E=3E specifics=2C the spirit of the tutorial is correct=2E=A0 =
I =

=3E strongly feel that
=3E =3E =3E=3E you should complete the tutorial before trying to go any =

=3E further with MC=5E2=2E
=3E =3E =3E=3E
=3E =3E =3E=3E The outline of the tutorial is=3A
=3E =3E =3E=3E 1=2E Take a copy of NoGC=2C called MyGC or something=2E=A0=
 Get =

=3E this building and
=3E =3E =3E=3E working=2E=A0 Lesson=3A how to create a =27new=27 GC plan=
=2C and =

=3E build and run it=2E
=3E =3E =3E=3E 2=2E Add a mark-sweep space to MyGC (ie build =

=3E MarkSweep)=2E=A0 Lesson=3A basics
=3E =3E =3E=3E collection of a new space=2E
=3E =3E =3E=3E 3=2E Add a copying nursery to MyGC=2C but perform full-he=
ap =

=3E collection at
=3E =3E =3E=3E every GC=2E=A0 This is the CopyMS collector=2E=A0 Lesson=3A=
 =

=3E handling copying spaces=2E
=3E =3E =3E=3E 4=2E Make the collector fully generational=2C by adding w=
rite =

=3E barriers and
=3E =3E =3E=3E separate nursery and mature space GC=2E=A0 Lesson=3A =

=3E handling remsets=2C
=3E =3E =3E=3E barriers and different =27flavours=27 of GC=2E
=3E =3E =3E=3E
=3E =3E =3E=3E Daniel and I will be happy to answer any questions you ha=
ve =

=3E getting=3E =3E=3E through the tutorial=2E=A0 While the exact details=
 =

=3E of the latest version are
=3E =3E =3E=3E not quite correct=2C the general outline of the tutorial =
is =

=3E still correct=2C
=3E =3E =3E=3E and is the best way we know of of coming to terms with ho=
w =

=3E MMTk works=2E
=3E =3E =3E=3E
=3E =3E =3E=3E cheers
=3E =3E =3E=3E Robin
=3E =3E =3E=3E
=3E =3E =3E=3E 100ji wrote=3A
=3E =3E =3E=3E=3E Hi all=2C
=3E =3E =3E=3E=3E
=3E =3E =3E=3E=3E I am trying to=A0 understand the current MMTk wrt to =

=3E the old MMTk as
=3E =3E =3E=3E=3E part of the MC=5E2 porting project=2E The old MMTk I a=
m =

=3E referring to is
=3E =3E =3E=3E=3E the one on which the old MC=5E2 code is based (approxi=
mately =

=3E Jikes 2=2E2=2E3
=3E =3E =3E=3E=3E version)=2C see attached Plan=2Ejava file that contain=
s an =

=3E implementation=3E =3E=3E=3E of MC=5E2 algo file for details=2E
=3E =3E =3E=3E=3E
=3E =3E =3E=3E=3E These are the few things I understood and a few questi=
ons =

=3E I have=2E
=3E =3E =3E=3E=3E Kindly verify if my understanding is accurate and answ=
er =

=3E the questions
=3E =3E =3E=3E=3E I have=2E
=3E =3E =3E=3E=3E
=3E =3E =3E=3E=3E Changes between old MMTk(oMMTk) and current MMTk(MMTk)=
=3A
=3E =3E =3E=3E=3E
=3E =3E =3E=3E=3E All the code in oMMTk was in the Plan class=2E=A0 In =

=3E MMTk=2C I noticed a few
=3E =3E =3E=3E=3E major changes=3A
=3E =3E =3E=3E=3E
=3E =3E =3E=3E=3E - Code has been split up into several classes=2E
=3E =3E =3E=3E=3E - The concept of phases has been added and has been us=
ed =

=3E by the
=3E =3E =3E=3E=3E StopTheWorld class from which all other classes inheri=
t=2E =

=3E Almost all of
=3E =3E =3E=3E=3E the processing in the sample GC=27s is being done in o=
ne of =

=3E the phases
=3E =3E =3E=3E=3E in collectionPhase methods=2E
=3E =3E =3E=3E=3E - The concept of Spaces has been added to ease handlin=
g spaces=2E
=3E =3E =3E=3E=3E - Memory handling has been abstracted out and at least=
 =

=3E from the looks
=3E =3E =3E=3E=3E of it=2C the user need not bother about the virtual ad=
dress =

=3E anymore=2E=3E =3E=3E=3E
=3E =3E =3E=3E=3E Currently=2C there is a single plan class that does gl=
obal
=3E =3E =3E=3E=3E initializations=2E For each application(mutator) threa=
d =

=3E there is a
=3E =3E =3E=3E=3E Mutator object (So=2C the number of mutator objects is=
 the =

=3E same as the
=3E =3E =3E=3E=3E number of application level threads)=2E Usually=2C the=
re is a =

=3E 1=3A1 mapping
=3E =3E =3E=3E=3E between application threads and kernel threads=2E For =
each =

=3E processor=3E =3E=3E=3E there is instance of the collector object=2E =

=3E Similarly=2C there is a
=3E =3E =3E=3E=3E global Trace object that handles the global tracing an=
d
=3E =3E =3E=3E=3E synchronisation=2E=A0 The TraceLocal object does the p=
er-
=3E thread related
=3E =3E =3E=3E=3E tracing=2E
=3E =3E =3E=3E=3E
=3E =3E =3E=3E=3E Is my understanding correct=3F
=3E =3E =3E=3E=3E
=3E =3E =3E=3E=3E Questions=3A
=3E =3E =3E=3E=3E
=3E =3E =3E=3E=3E - Is there file/document that lists the order in which=
 the =

=3E methods in
=3E =3E =3E=3E=3E these classes are called=A0 for a simple algorithm=3F =
If =

=3E this exists=2C it
=3E =3E =3E=3E=3E will make my understanding of the whole system much mu=
ch =

=3E more simpler=2E
=3E =3E =3E=3E=3E - Is there code for a GC algo in the latest release th=
at =

=3E is closest to
=3E =3E =3E=3E=3E MC=5E2 algo=3F
=3E =3E =3E=3E=3E - Does java spec mandate that there should be a 1=3A1 =

=3E mapping between an
=3E =3E =3E=3E=3E application thread and an OS thread=3F
=3E =3E =3E=3E=3E - What does =22heap is full=22 mean in a generational =
garbage =

=3E collector=3F=3E =3E=3E=3E Why don=27t we say older generation is ful=
l instead=3F
=3E =3E =3E=3E=3E - Can anyone please take a look at the attached Plan=2E=
java =

=3E file and
=3E =3E =3E=3E=3E give me a brief overview of how to port the algo=2E I =
have =

=3E sort of
=3E =3E =3E=3E=3E understood parts of the file=2C but I am clueless on h=
ow I =

=3E should be
=3E =3E =3E=3E=3E implementing an incremental marking and copying in the=
 old =

=3E code using
=3E =3E =3E=3E=3E the phases in StopTheWorld GC=2E
=3E =3E =3E=3E=3E
=3E =3E =3E=3E=3E MC=5E2=5B1=5D Specific questions=3A
=3E =3E =3E=3E=3E
=3E =3E =3E=3E=3E=A0=A0=A0=A0 - In MC=5E2 algo the older =

=3E generation is divided into multiple windows=2E
=3E =3E =3E=3E=3E Each window from a high level can be thought of as a g=
eneration
=3E =3E =3E=3E=3E itself=2C with an incremental marking and copying mech=
anism =

=3E that works
=3E =3E =3E=3E=3E across all these windows=2E
=3E =3E =3E=3E=3E=A0=A0=A0=A0=A0=A0=A0=A0 - How do I =

=3E implement this feature=3F
=3E =3E =

=3E =3E=3E=3E=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 - Does using =
CopySpace per window work=3F
=3E =3E =3E=3E=3E=A0=A0=A0=A0=A0=A0=A0=A0 - Should I =

=3E be using Spaces=3F Is there any Space already that
=3E =3E =3E=3E=3E exhibits
=3E =3E =3E=3E=3E similar properties=3F
=3E =3E =3E=3E=3E=A0=A0=A0=A0=A0=A0=A0=A0 - How much =

=3E work would it be to implement a Space with the above
=3E =3E =3E=3E=3E properties=3F
=3E =3E =3E=3E=3E=A0=A0=A0=A0 - Can MC=5E2 be used in non-
=3E generational mode=3F Will it be efficient=3F
=3E =3E =3E=3E=3E
=3E =3E =3E=3E=3E More later =3A)=2E
=3E =3E =3E=3E=3E
=3E =3E =3E=3E=3E Thanks for your time=2C
=3E =3E =3E=3E=3E -Sowjanya
=3E =3E =3E=3E=3E
=3E =3E =3E=3E=3E =5B1=5D http=3A//www=2Ecs=2Eumass=2Eedu/=7Eemery/pubs/=
04-15=2Epdf
=3E =3E =3E=3E=3E
=3E =3E =3E=3E=3E
=3E =3E =3E=3E=3E ------------------------------------------------------=
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=3E =3E =3E=3E --
=3E =3E =3E=3E Robin Garner
=3E =3E =3E=3E Dept=2E of Computer Science
=3E =3E =3E=3E Australian National University
=3E =3E =3E=3E http=3A//cs=2Eanu=2Eedu=2Eau/people/Robin=2EGarner/
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=3E =3E --
=3E =3E Robin Garner
=3E =3E Dept=2E of Computer Science
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