Right, I see this is what happens when I'm out of touch for a few days.
Anyways, the whole single or multiple address space design issue can be
dealt with later. Page tables are going to be implemented regardless (we
need them for paging purposes anyways) and I intend to do MAS for the time
being (since it actually simplifies a few things for us). We can experiment
with SAS on x64, once we get there.
Anyways, as pointed out by Grover, there has to be something at the lowest
level of the OS to handle the basic memory allocations and whatnot.
Anything dealing with objects and the like need something already existing
to sit atop of and that is what I am trying to implement now. We can save
all the fancy object stuff for the GC, or we could go the NT route and have
everything as objects. Regardless, we still need to get the foundations set
before we can get too ambitious.
On Mon, Jul 21, 2008 at 5:07 PM, Sander van Rossen <[EMAIL PROTECTED]>
wrote:
> We also need to decide how to implement virtual memory.
> Before we where talking about using a single page-table (or maybe just
> a handful) for the entire system, because this would allow us to not
> slow down the system with page-table switches.. but on a 32 bit system
> with 4gb memory this is pretty hard to do.
> We could drop the "single page-table" idea, decide to go 64-bit only,
> or something else.. but we need to define it.
>
>
> On Sun, Jul 20, 2008 at 9:23 AM, grover <[EMAIL PROTECTED]> wrote:
> > Hi Adam,
> > something like that could work, but there is still the problem that you
> have
> > to locate the object in memory in a heap, which will later on be
> maintained
> > by the GC. There are some low-level services, which IMHO just can't be
> > wrapped in object instances - as they are essentially singletons. Memory
> > management should be split into five pieces IMHO:
> > 1. A physical memory manager, which gives out 4KB pages of physical
> address
> > space
> > 2. A process memory manager, which manages virtual memory and acquires
> > physical pages on demand
> > 3. A pager, which moves virtual pages between disk and physical memory
> > 4. A heap manager, which is responsible for the actual object allocation
> > 5. A GC which returns regions to the heap
> > At least #1,3 are singletons with respect to system lifetimes. #2,4,5 are
> > per-process singletons.
> > Maybe we could think about your design of using adapter or strategy
> objects
> > to wrap the access to these services in your design? This way the
> adapters
> > could implement the interfaces you need and abstract away the access to
> the
> > actual service implementations.
> > Mike
> > Am 20.07.2008 um 00:34 schrieb Adam Stevenson:
> >
> > Howdy Mike,
> >
> > I am thinking what we need to do is figure out what format the objects
> are
> > going to need to look like in memory when a memory manager / GC are in
> > place. This way, when the MM and GC come online during the boot up, they
> > can "take over" objects that were previously not managed, and the initial
> > memory manager can keep a list of memory allocated that is not yet been
> > assigned to a memory manager - thus making it easy to identify objects.
> > Think this approach could work? If so, we just need to figure out how we
> > want to structure the unmanaged memory / objects, so that their
> structures
> > can be compatible.
> >
> > -Adam
> >
> > On Sat, Jul 19, 2008 at 5:21 AM, Matthijs ter Woord
> > <[EMAIL PROTECTED]> wrote:
> >>
> >> Ah, you guys are trying to instantiate the memory manager. Hmm..
> >>
> >>
> >>
> >>
> >> From: [EMAIL PROTECTED]
> >> [mailto:[EMAIL PROTECTED] On Behalf Of
> >> grover
> >> Sent: zaterdag 19 juli 2008 11:31
> >> To: sharpos-developers@lists.sourceforge.net
> >> Subject: Re: [SharpOS Developers] Memory manager designand
> >> overallcompartmentalization
> >>
> >>
> >>
> >> Matthijs, you're right. However it still doesn't solve the problem that
> >> you want to new a memory manager without having a memory manager to
> allocate
> >> one from ;) SharpOS doesn't have a GC with the current memory management
> >> facilities either. I see it more of a structural problem than a
> technical
> >> one and thus I see it more like a design issue.
> >>
> >>
> >>
> >> Mike
> >>
> >>
> >> ________________________________
> >>
> >> Von: [EMAIL PROTECTED]
> >> [mailto:[EMAIL PROTECTED] Im Auftrag
> von
> >> Matthijs ter Woord
> >> Gesendet: Samstag, 19. Juli 2008 11:04
> >> An: sharpos-developers@lists.sourceforge.net
> >> Betreff: Re: [SharpOS Developers] Memory manager designand
> >> overallcompartmentalization
> >>
> >> An option is maybe this:
> >>
> >>
> >>
> >> Make a fake memory manager, which only is able to allocate (ie, it never
> >> takes back memory). For most basic operations you don't use too much
> >> objects, so you can live without a GC for a while too. This way you can
> >> start on Object support, then interface support, while not having issues
> >> with GC and memory manager.
> >>
> >>
> >>
> >> We do it that way in Cosmos. We don't have a memorymanager capable of
> >> freeing memory, neither do we have a GC (we have the code in place to
> plug
> >> one in, but don't have one. Ralf just started on this)….
> >>
> >>
> >>
> >> From: [EMAIL PROTECTED]
> >> [mailto:[EMAIL PROTECTED] On Behalf Of
> >> grover
> >> Sent: zaterdag 19 juli 2008 10:16
> >> To: sharpos-developers@lists.sourceforge.net
> >> Subject: Re: [SharpOS Developers] Memory manager design and
> >> overallcompartmentalization
> >>
> >>
> >>
> >> Hi Adam,
> >>
> >>
> >>
> >> the AOT does support interfaces. There were some bugs, but they
> shouldn't
> >> stop us there. There's only one problem: For interfaces to work you need
> >> object instances and new/GC... Which causes us a kind of chicken & egg
> >> problem. At least at the level Zachary is working at, we need to stay
> with
> >> static classes. I understand your goals, but unless you can give me a
> hint
> >> how you want to manage it without the chicken&egg situation I don't have
> any
> >> idea.
> >>
> >>
> >>
> >> Mike
> >>
> >>
> >> ________________________________
> >>
> >> Von: [EMAIL PROTECTED]
> >> [mailto:[EMAIL PROTECTED] Im Auftrag
> von
> >> Adam Stevenson
> >> Gesendet: Freitag, 18. Juli 2008 06:44
> >> An: sharpos-developers@lists.sourceforge.net
> >> Betreff: Re: [SharpOS Developers] Memory manager design and
> >> overallcompartmentalization
> >>
> >> Howdy Zachary and All,
> >>
> >> Yes, I believe that we do need to do a good restructruring. I have a
> >> bunch of ideas I have been hashing out in my sandbox, but I there are
> parts
> >> that I am not sure exactly what is going on (some parts get cryptic, any
> >> understand the process of preparing the image fully?). I first think we
> >> need a high level diagram of all the major components, so we can start
> >> figuring out where we can make plugable modules. From my own project
> work,
> >> and my experience with biologcial systems, we need to slowly evolve this
> and
> >> not break it. (I know duh).
> >>
> >> First does thing support interfaces yet? Because I don't see much of
> them
> >> in the code base. If not, I say we work on making a list of abstract
> >> classes that we can start keying in as modules. I know Grover has been
> >> working on a lot of this, and we need to get his input on the AOT
> plugable
> >> architecture. Anyone going to be around Sunday afternoon (CST) - or
> most
> >> anytime Monday (minus 3:00 to 5:00 CST)? I can sit down online with
> anyone
> >> and start diagraming some of this stuff and work a bit in team mode -
> >> identify document, and review. And then we can send out whatever
> documents
> >> we get done via the list serve, and continue to move on ot the next.
> Anyone
> >> up for it?
> >>
> >> As for what I have been working on is a bunch of class processing stuff,
> >> and memory structuring of components. I want to build an architecture
> that
> >> you could say is "fractal" - thus allowing for the same archtiecture
> whether
> >> a JIT is being ran on top of a JIT (pretty dang inefficient) or is
> actaul
> >> the JIT. To do this, everything needs to be turned into an interface,
> to
> >> allow for components to shift up and down. I have started looking into
> how
> >> to structure this namespace and working on a prototype base, but it is
> not
> >> compable yet (on my to do list for next week). But bottom line, this is
> >> still a long way off from where the AOT and SharpOS is now, so this is
> by
> >> now means a fully workable design that SharpOS can be converted too.
> Plus
> >> there are some differences in concepts too with the idea of runtime and
> OS
> >> that are going to have to be hashed out.
> >>
> >> So personally, we need to look at all of us "newbies' fully
> understanding
> >> what we have, and second we slowly turn this thing modular and make a
> list
> >> of all the modules and what their requirements are, so the code base can
> be
> >> evolved in small parts versus changing one thing causes a bunch of
> ripple
> >> effects throughout the code. My guess, a lot of this modularity already
> >> exists, but we just need to uncover dividing points. So back to Sunday
> and
> >> Monday for me. Anyone game? And thoughts on how we want to start
> breaking
> >> up this code base into smaller understandable pieces? Oh Zachary, I got
> >> both those books on Memory Management and Garbage Collection - need to
> >> finish them, but if you have concepts to reference, just let me know
> page
> >> numbers.
> >>
> >> Adam Stevenson
> >>
> >> Graduate Student
> >> Department of Biology
> >> Texas A&M University
> >> College Station, TX 77843, USA
> >>
> >> On Wed, Jul 16, 2008 at 10:03 AM, Zachary Gorden
> >> <[EMAIL PROTECTED]> wrote:
> >>
> >> Just a clarification, when I say memory manager, I mean from the page
> >> tables to the physical memory table to the allocations. It seems that
> >> people keep confusing what I am referring to whenever I say MM. This is
> >> mostly an informational thing to let people know what's going through my
> >> head and the fact that I'm not dead and still working/planning.
> >>
> >> The memory manager as it stands suffers from a somewhat awkward design
> >> that makes it difficult to correct certain items. Not exactly anyone's
> >> fault, as SharpOS needed a MM and that's what it got. The gist is,
> trying
> >> to fix the issues in here and/or optimizing it won't do much in the long
> >> term, which is one reason you guys haven't seen much activity from me.
> >>
> >> I've been mostly consulting a few ROS developers on how to bootstrap a
> >> page table based MM, the initial loading and stuff, so that's the
> >> explanation for the lack of code. For the time being, I've gotten most
> of
> >> the conceptual things explained and will be writing out some of my own
> code
> >> as well as examining just what kind of support for paging exists right
> now.
> >> And actually, in the process of trying to look at the current code,
> another
> >> thought occurred to me. Currently, the ADC is, to put it simply,
> horribly
> >> organized. It's basically all of the AD code in one spot, without any
> >> actual segmentation. That is definitely going to screw with us down the
> >> line, and it is likely to not be limited to the ADC.
> >>
> >> Because of the above reasons, I am most definitely going to need to
> create
> >> a branch (once I figure out how), as obviously doing surgery on trunk is
> >> going to result in incredible instabilities and breakages. But as far
> as
> >> the restructuring goes, I think a lot of us would benefit from such
> changes,
> >> including people already working with their own branches. I'd like to
> hear
> >> from other people on the restructuring idea, as I know I'm not the only
> one
> >> who noticed the issues.
> >>
> >>
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