On 9/23/05, Robin Garner <[EMAIL PROTECTED]> wrote: > Weldon Washburn wrote: > > > Everyone, > > I just posted the basics of the GC/VM interface to > > http://wiki.apache.org/harmony/HarmonyArchitecture. The VM calls into > > the GC using gc_interface.txt. The GC calls into the VM using > > vm_gc_interface.txt. > > Weldon > > > > > Thanks Weldon, it makes very interesting reading. I've posted a > description of MMTk's VM interface on my web page, > http://cs.anu.edu.au/people/Robin.Garner/, for comparison. This is the > GC -> VM interface.
Great! Its good you are documenting MMTk interface. I will take a look at it soon. Please think of the interfaces that I posted as a starting point. Also, don't feel shy about ripping apart the interfaces I have posted. The whole point is to quickly evolve Harmony into something more sophisticated than the existing JVMs. > > As described in my thesis (although if you want to read it, remember it > is now nearly 2 years out of date, and MMTk has moved on - link is also > on my ANU web page), we follow a "wedge" model of the interface, rather > than specifying a simple flat API. So while JikesRVM (and Rotor and > JNode) have a definite API that they code to, there is a package that > translates this to fit the services MMTk offers. And that's a large > set, not yet documented (beyond source and javadoc in any case). > > I'm going to look more closely at the interface you've posted, and will > probably have more questions in a short while, but my first > impressions/questions are: > - The interface seems tightly coupled to ORP and Sapphire. Sapphire has been backed out of the source base. As far as I know, the GC interface I posted has not been used any place but ORP and its follow-ons. > For example, > since there aren't any API calls to do it, I presume the GC knows how > the object header is laid out ? And knows about something called a > vtable ? True and true. > - It's not explicitly specified in the API, but I assume gc_alloc_fast > is inlined (or is a macro) ? gc_alloc_fast is intended to be inlined. > - Doesn't supporting gc_pin_object restrict the GC implementation > significantly ? This might have been one of the APIs left over from when we extended ORP to run ECMA CLI (.net). I might have forgotten to remove it. > - I was under the impression ORP doesn't yet support weak references or > finalizers. Stay tuned for more info. > There appears to be support for the GC to tell the VM about > reference types, but not the other way round. Is this right ? Or is > this the gc_add_weak_root_set_entry call ? > - How does the VM enumerate the thread stacks ? Is this the > gc_add_root_set_entry call ? I will have to take a look and get back to you. > > Do you have any documentation specifying what else the GC talks to ? > I'm assuming that for its own synchronization, interfacing with the OS > (mmap etc) it talks directly with the OS, glibc etc. Yes. I have been waiting to see what response I get to what's already posted before posting more stuff. > > Cheers, > Robin > > -- Weldon Washburn Intel Managed Runtime Division
