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From "Rana Dasgupta" <rdasg...@gmail.com>
Subject Re: [drlvm] Class unloading support
Date Sat, 28 Oct 2006 01:13:36 GMT
I completely agree.

+1 for branch if Aleksey wants to experiment


On 10/27/06, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
>
> All, I think the problem now is mainly about the class unloading
> design not about whether class unloading happens in server
> environment.
>
> Class unloading is definitely a feature required in future; but with
> the significance of the required modifications in JVM by this class
> unloading design 2 (using Java object for Vtable), it is probably
> safer to move this work into a branch at the moment until all other
> components are ready for it, and after we have thorough evaluation on
> it since there are still issues to be resolved or discussed.
>
> Or we can keep it in JIRA and keep the discussion and evaluation going
> on before we decide to support the special design (Java Vtable) in
> other components.
>
> How about it?
>
> Thanks,
> xiaofeng
>
> On 10/27/06, Geir Magnusson Jr. <geir@pobox.com> wrote:
> >
> >
> > Rana Dasgupta wrote:
> > > My knowledge in this area is limited. But my understanding was that
> web
> > > servers and other similar hosts recycled processes periodically as
> > > standard procedure, thereby tearing down all associated resources.
> >
> > Yes, but that has nothing to do with what would be happening in the app
> > server the web server talked to, if one had an architecture where a web
> > server "fronted" for the app server.
> >
> > > So
> > > classes loaded, but not used for a while went away anyway;
> >
> > Nope - they aren't loaded in the context of the webserver (when using
> > httpd).
> >
> > > this level of
> > > resource management was not really urgent. I know that IIS does this,
> I
> > > am not sure about httpd. I am not sure about other host environments.
> >
> > But a process fork model (or thread model) of a webserver has nothing to
> > do with what's going on in the VM.
> >
> > I'm talking about servlet engines and app servers like Tomcat and
> > Geronimo which have nothing to do with httpd.  Architecturally, they are
> > separated from the web server (unless you don't use an external
> > webserver, and just use the httpd connector in tomcat) and are separate,
> > independent processes.
> >
> >      httpd  <------>  Tomcat
> >
> > The java-based app servers are long running processes, running for weeks
> > or months.  We need to do clean class unloading.
> >
> > geir
> >
> >
> > >
> > >
> > > On 10/27/06, *Geir Magnusson Jr.* <geir@pobox.com
> > > <mailto:geir@pobox.com>> wrote:
> > >
> > >
> > >
> > >     Rana Dasgupta wrote:
> > >      > Aleksey,
> > >      >   I had a couple of questions.
> > >      >   You state that DRLVM does not implement the class unloading
> > >     optimization,
> > >      > and this may create memory pressure on some applications that
> > >     load many
> > >      > classes. Do we have a real case / example where an application
> is
> > >     stuck for
> > >      > insufficient memory because it uses a lot of classes initially
> > >     and then
> > >      > stops using them, but these are not unloaded? One can imagine a
> > >     web browser
> > >      > doing something like this. Is a web browser a typical use case
> > >     for the
> > >      > Harmony JVM?
> > >      >
> > >
> > >     If I understand what you're asking correctly, you'll find this
> pattern
> > >     in servlet engines or J2EE servers, where deployed apps can be
> dumped
> > >     and reloaded repeatedly either during development or during
> production
> > >     deployment, w/o taking the server down.
> > >
> > >     geir
> > >
> > >
> >
>

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