Question about MemoryService class.

[Colin(Du Li)]

Hi, guys.

Could you give me some information about MemoryService in hotspot. It seems like a tool to monitor the memory usage, right? But it only support 2 generations. I wanna divide the heap into three generations, so it gives me error information. Can I turn it off? Will it cause problems if I turn it off. How can I turn it off without side effect?
Thanks a lot!

Colin(Du Li)

[Tom Rodriguez]

Can't you just fix MemoryService to handle more than 2 generations?  
It doesn't look that complicated.

tom

On Feb 6, 2009, at 1:19 PM, Colin(Du Li) wrote:

>
> Hi, guys.
>
> Could you give me some information about MemoryService in hotspot.  
> It seems
> like a tool to monitor the memory usage, right? But it only support 2
> generations. I wanna divide the heap into three generations, so it  
> gives me
> error information. Can I turn it off? Will it cause problems if I  
> turn it
> off. How can I turn it off without side effect?
> Thanks a lot!
>
> Colin(Du Li)
> --
> View this message in context: http://www.nabble.com/Question-about-MemoryService-class.-tp21880830p21880830.html
> Sent from the OpenJDK Hotspot Virtual Machine mailing list archive  
> at Nabble.com.
>

[mandy.chung]

Colin(Du Li) wrote:

>Hi, guys.
>
>Could you give me some information about MemoryService in hotspot. It seems
>like a tool to monitor the memory usage, right? But it only support 2
>generations. I wanna divide the heap into three generations, so it gives me
>error information. Can I turn it off? Will it cause problems if I turn it
>off. How can I turn it off without side effect?
>  
>
The memoryService and memory pool implementation is the VM support for
the java.lang.management API.  

You need to change the current implementation to support 3 generations.  
The memory pool/service implementation is not limited to 2 generations.

Mandy

>Thanks a lot!
>
>Colin(Du Li)
>  
>

[Colin(Du Li)]

Thanks a lot！
I have fixed it.
To constrain the two-generation collector makes the system less extensible.
I wonder this part will be improve the the future.

mandy.chung wrote:

Colin(Du Li) wrote:

>Hi, guys.
>
>Could you give me some information about MemoryService in hotspot. It seems
>like a tool to monitor the memory usage, right? But it only support 2
>generations. I wanna divide the heap into three generations, so it gives me
>error information. Can I turn it off? Will it cause problems if I turn it
>off. How can I turn it off without side effect?
>  
>
The memoryService and memory pool implementation is the VM support for
the java.lang.management API.  

You need to change the current implementation to support 3 generations.  
The memory pool/service implementation is not limited to 2 generations.

Mandy

>Thanks a lot!
>
>Colin(Du Li)
>  
>

[y.s.ramakrishna]

Hi Colin --

If you have a use case where 3 or more generations will
provide distinct advantages, please feel free to
propose an OpenJDK project for this and we'll be
happy to help you navigate around in the relevant parts of
the source code so you can get this done. The basic
functionality will likely be quite straightforward,
if tedious in some of the details, and in limiting
the performance impact upon the basic 2 generation system.

-- ramki

----- Original Message -----
From: "Colin(Du Li)" <dawn2004@...>
Date: Saturday, February 7, 2009 11:08 am
Subject: Re: Question about MemoryService class.
To: hotspot-dev@...

> Thanks a lot！
> I have fixed it.
> To constrain the two-generation collector makes the system less extensible.
> I wonder this part will be improve the the future.
>
>
> mandy.chung wrote:
> >
> > Colin(Du Li) wrote:
> >
> >>Hi, guys.
> >>
> >>Could you give me some information about MemoryService in hotspot. It
> seems
> >>like a tool to monitor the memory usage, right? But it only support
> 2
> >>generations. I wanna divide the heap into three generations, so it gives
> me
> >>error information. Can I turn it off? Will it cause problems if I
> turn it
> >>off. How can I turn it off without side effect?
> >>  
> >>
> > The memoryService and memory pool implementation is the VM support
> for
> > the java.lang.management API.  
> >
> > You need to change the current implementation to support 3
> generations.  
> > The memory pool/service implementation is not limited to 2 generations.
> >
> > Mandy
> >
> >>Thanks a lot!
> >>
> >>Colin(Du Li)
> >>  
> >>
> >
> >
> >
>
> --
> View this message in context: http://www.nabble.com/Question-about-MemoryService-class.-tp21880830p21891770.html
> Sent from the OpenJDK Hotspot Virtual Machine mailing list archive at
> Nabble.com.
>

[y.s.ramakrishna]

of course, G1 and the possibilities/flexibility it allows
probably makes something like this somewhat moot (at least as
far as my intuition goes here).

-- ramki

----- Original Message -----
From: Y Srinivas Ramakrishna <Y.S.Ramakrishna@...>
Date: Saturday, February 7, 2009 1:09 pm
Subject: Re: Question about MemoryService class.
To: "Colin(Du Li)" <dawn2004@...>
Cc: hotspot-dev@...

> Hi Colin --
>
> If you have a use case where 3 or more generations will
> provide distinct advantages, please feel free to
> propose an OpenJDK project for this and we'll be
> happy to help you navigate around in the relevant parts of
> the source code so you can get this done. The basic
> functionality will likely be quite straightforward,
> if tedious in some of the details, and in limiting
> the performance impact upon the basic 2 generation system.
>
> -- ramki
>
> ----- Original Message -----
> From: "Colin(Du Li)" <dawn2004@...>
> Date: Saturday, February 7, 2009 11:08 am
> Subject: Re: Question about MemoryService class.
> To: hotspot-dev@...
>
>
> > Thanks a lot！
> > I have fixed it.
> > To constrain the two-generation collector makes the system less extensible.
> > I wonder this part will be improve the the future.
> >
> >
> > mandy.chung wrote:
> > >
> > > Colin(Du Li) wrote:
> > >
> > >>Hi, guys.
> > >>
> > >>Could you give me some information about MemoryService in hotspot.
> It
> > seems
> > >>like a tool to monitor the memory usage, right? But it only
> support
> > 2
> > >>generations. I wanna divide the heap into three generations, so it
> gives
> > me
> > >>error information. Can I turn it off? Will it cause problems if I
>
> > turn it
> > >>off. How can I turn it off without side effect?
> > >>  
> > >>
> > > The memoryService and memory pool implementation is the VM support
>
> > for
> > > the java.lang.management API.  
> > >
> > > You need to change the current implementation to support 3
> > generations.  
> > > The memory pool/service implementation is not limited to 2 generations.
> > >
> > > Mandy
> > >
> > >>Thanks a lot!
> > >>
> > >>Colin(Du Li)
> > >>  
> > >>
> > >
> > >
> > >
> >
> > --
> > View this message in context: http://www.nabble.com/Question-about-MemoryService-class.-tp21880830p21891770.html
> > Sent from the OpenJDK Hotspot Virtual Machine mailing list archive
> at
> > Nabble.com.
> >

[Colin(Du Li)]

Hi, ramki,

Thanks you for your reply.
Does G1 mean the "generation 1" in generational GC?
Why do you think it might be moot? I wonder if you can give more explanations.
Thanks.

Colin.

y.s.ramakrishna wrote:

of course, G1 and the possibilities/flexibility it allows
probably makes something like this somewhat moot (at least as
far as my intuition goes here).

-- ramki

----- Original Message -----
From: Y Srinivas Ramakrishna <[e-mail]>
Date: Saturday, February 7, 2009 1:09 pm
Subject: Re: Question about MemoryService class.
To: "Colin(Du Li)" <[e-mail]>
Cc: [e-mail]


> Hi Colin --
>
> If you have a use case where 3 or more generations will
> provide distinct advantages, please feel free to
> propose an OpenJDK project for this and we'll be
> happy to help you navigate around in the relevant parts of
> the source code so you can get this done. The basic
> functionality will likely be quite straightforward,
> if tedious in some of the details, and in limiting
> the performance impact upon the basic 2 generation system.
>
> -- ramki
>
> ----- Original Message -----
> From: "Colin(Du Li)" <[e-mail]>
> Date: Saturday, February 7, 2009 11:08 am
> Subject: Re: Question about MemoryService class.
> To: [e-mail]
>
>
> > Thanks a lot！
> > I have fixed it.
> > To constrain the two-generation collector makes the system less extensible.
> > I wonder this part will be improve the the future.
> >
> >
> > mandy.chung wrote:
> > >
> > > Colin(Du Li) wrote:
> > >
> > >>Hi, guys.
> > >>
> > >>Could you give me some information about MemoryService in hotspot.
> It
> > seems
> > >>like a tool to monitor the memory usage, right? But it only
> support
> > 2
> > >>generations. I wanna divide the heap into three generations, so it
> gives
> > me
> > >>error information. Can I turn it off? Will it cause problems if I
>
> > turn it
> > >>off. How can I turn it off without side effect?
> > >>  
> > >>
> > > The memoryService and memory pool implementation is the VM support
>
> > for
> > > the java.lang.management API.  
> > >
> > > You need to change the current implementation to support 3
> > generations.  
> > > The memory pool/service implementation is not limited to 2 generations.
> > >
> > > Mandy
> > >
> > >>Thanks a lot!
> > >>
> > >>Colin(Du Li)
> > >>  
> > >>
> > >
> > >
> > >
> >
> > --
> > View this message in context: http://www.nabble.com/Question-about-MemoryService-class.-tp21880830p21891770.html
> > Sent from the OpenJDK Hotspot Virtual Machine mailing list archive
> at
> > Nabble.com.
> >

[y.s.ramakrishna]

[I am cross-posting on to the hotspot-gc-dev list, since
that's likely where this discussion belongs; i'll bcc
the hotspot-dev list on this response, so interested folk can
follow the discussion on the former list.]

Sorry about the cryptic note.
G1 is short-hand (within HotSpot circles) of
the "Garbage-First Garbage Collector" which was
checked into the open jdk repos a few months ago.
For related background, see:-

http://portal.acm.org/citation.cfm?id=1029879

@inproceedings{1029879,
 author = {Detlefs,, David and Flood,, Christine and Heller,, Steve and Printezis,, Tony},
 title = {Garbage-first garbage collection},
 booktitle = {ISMM '04: Proceedings of the 4th international symposium on Memory management},
 year = {2004},
 isbn = {1-58113-945-4},
 pages = {37--48},
 location = {Vancouver, BC, Canada},
 doi = {http://doi.acm.org/10.1145/1029873.1029879},
 publisher = {ACM},
 address = {New York, NY, USA},
 }


I am thinking that the latitude allowed by the basic
collection set mechanism and the ability to collect an
arbitrary collection set at specific points,
should, in principle, allow a range of policies
for the choice of specific collection sets at specific
times, allowing one to simulate, in effect, an arbitrary
n-generation system by means of segregating objects into
collection sets by age. Much handwaving here; and,
as usual, the devil's in the details... so consider this
loud thinking about possible approaches, rather than
concrete direction.

over and out.
-- ramki

----- Original Message -----
From: "Colin(Du Li)" <dawn2004@...>
Date: Saturday, February 7, 2009 1:25 pm
Subject: Re: Question about MemoryService class.
To: hotspot-dev@...

> Hi, ramki,
>
> Thanks you for your reply.
> Does G1 mean the "generation 1" in generational GC?
> Why do you think it might be moot? I wonder if you can give more
> explanations.
> Thanks.
>
> Colin.
>
> y.s.ramakrishna wrote:
> >
> >
> > of course, G1 and the possibilities/flexibility it allows
> > probably makes something like this somewhat moot (at least as
> > far as my intuition goes here).
> >
> > -- ramki
> >
> > ----- Original Message -----
> > From: Y Srinivas Ramakrishna <Y.S.Ramakrishna@...>
> > Date: Saturday, February 7, 2009 1:09 pm
> > Subject: Re: Question about MemoryService class.
> > To: "Colin(Du Li)" <dawn2004@...>
> > Cc: hotspot-dev@...
> >
> >
> >> Hi Colin --
> >>
> >> If you have a use case where 3 or more generations will
> >> provide distinct advantages, please feel free to
> >> propose an OpenJDK project for this and we'll be
> >> happy to help you navigate around in the relevant parts of
> >> the source code so you can get this done. The basic
> >> functionality will likely be quite straightforward,
> >> if tedious in some of the details, and in limiting
> >> the performance impact upon the basic 2 generation system.
> >>
> >> -- ramki
> >>
> >> ----- Original Message -----
> >> From: "Colin(Du Li)" <dawn2004@...>
> >> Date: Saturday, February 7, 2009 11:08 am
> >> Subject: Re: Question about MemoryService class.
> >> To: hotspot-dev@...
> >>
> >>
> >> > Thanks a lot！
> >> > I have fixed it.
> >> > To constrain the two-generation collector makes the system less
> >> extensible.
> >> > I wonder this part will be improve the the future.
> >> >
> >> >
> >> > mandy.chung wrote:
> >> > >
> >> > > Colin(Du Li) wrote:
> >> > >
> >> > >>Hi, guys.
> >> > >>
> >> > >>Could you give me some information about MemoryService in
> hotspot.
> >> It
> >> > seems
> >> > >>like a tool to monitor the memory usage, right? But it only
> >> support
> >> > 2
> >> > >>generations. I wanna divide the heap into three generations, so
> it
> >> gives
> >> > me
> >> > >>error information. Can I turn it off? Will it cause problems if
> I
> >>
> >> > turn it
> >> > >>off. How can I turn it off without side effect?
> >> > >>  
> >> > >>
> >> > > The memoryService and memory pool implementation is the VM
> support
> >>
> >> > for
> >> > > the java.lang.management API.  
> >> > >
> >> > > You need to change the current implementation to support 3
> >> > generations.  
> >> > > The memory pool/service implementation is not limited to 2
> >> generations.
> >> > >
> >> > > Mandy
> >> > >
> >> > >>Thanks a lot!
> >> > >>
> >> > >>Colin(Du Li)
> >> > >>  
> >> > >>
> >> > >
> >> > >
> >> > >
> >> >
> >> > --
> >> > View this message in context:
> >> http://www.nabble.com/Question-about-MemoryService-class.-tp21880830p21891770.html
> >> > Sent from the OpenJDK Hotspot Virtual Machine mailing list
> archive
> >> at
> >> > Nabble.com.
> >> >
> >
> >
>
> --
> View this message in context: http://www.nabble.com/Question-about-MemoryService-class.-tp21880830p21892968.html
> Sent from the OpenJDK Hotspot Virtual Machine mailing list archive at
> Nabble.com.
>

[Tomas Hurka]

Hi Colin,
On 7 Feb 2009, at 22:23, Colin(Du Li) wrote:
>
> Thanks you for your reply.
> Does G1 mean the "generation 1" in generational GC?
G1 is a short name for Garbage-First garbage collector developed by  
HotSpot team.
For more details see <http://developers.sun.com/learning/javaoneonline/j1sessn.jsp?sessn=TS-5419&yr=2008&track=javase 
 >

Bye,
--
Tomas Hurka   <mailto:tomas.hurka@...>
NetBeans Profiler http://profiler.netbeans.org
VisualVM http://visualvm.dev.java.net
Software Engineer, Developer Platforms Group
Sun Microsystems, Praha Czech Republic