On 01 Nov 2006 16:05:41 +0600, Egor Pasko <[EMAIL PROTECTED]> wrote:
On the 0x214 day of Apache Harmony Mikhail Fursov wrote: > On 01 Nov 2006 15:56:28 +0600, Egor Pasko <[EMAIL PROTECTED]> wrote: > > > > agreed. not patching .. just reporting 'golden' VTable refs to GC, am > > I right? > > > Yes, and everytime we report it to GC and GC moves an object - it patches > the address we report. so, by saying "patching" you insist to put immediate operands into instructions? That's probably worth it, but it extends the JIT<->GC interface. How about making a simple operand (reg/mem) as the first step?
Egor, I thinks this is slightly more complicated problem. If vtable object is moved we must update all devirtualization points in every method compiled before. It can require an extension of JIT<->VM<->GC interface. Another solution I see is to collect info about all devirtualization points in JIT (code addrs) and report these addresses as enumeration roots. This is JIT-only solution, and disadvantage is a significant (~hot methods count) increase of number of objects reported. On the other hand I see no reasons to unpin vtables in the nearest future (Let's GC guru correct me). If you use special (freelist-type ?) allocator in GC the memory fragmentation when unloading pinned vtable objects could be low. -- Mikhail Fursov
