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From "Xiao-Feng Li (JIRA)" <j...@apache.org>
Subject [jira] Assigned: (HARMONY-4282) [drlvm][gc] obj_info agreement between VM and GC
Date Tue, 26 Jun 2007 08:05:26 GMT

     [ https://issues.apache.org/jira/browse/HARMONY-4282?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Xiao-Feng Li reassigned HARMONY-4282:

    Assignee: Xiao-Feng Li

> [drlvm][gc] obj_info agreement between VM and GC
> ------------------------------------------------
>                 Key: HARMONY-4282
>                 URL: https://issues.apache.org/jira/browse/HARMONY-4282
>             Project: Harmony
>          Issue Type: Wish
>          Components: DRLVM
>         Environment: All
>            Reporter: Li-Gang Wang
>            Assignee: Xiao-Feng Li
> The original assumption on obj_info is new object has no obj_info. But I think this is
not convenient or necessarily correct to utilize obj_info sufficiently.
> For example, in order to know an object is a small (<= small_threshold) or large (>large_threshold)
object, checking a bit in obj_info is more time-saving than searching its size through function
vm_object_size. This needs the according bit in obj_info to be set while allocating. But under
the original assumption, VM will reset obj_info after allocation sometimes, so that this bit
will be misleading. The following is the code resetting obj_info:
> jobject object_clone(JNIEnv *jenv, jobject jobj)
> {
>     ......
>   result = (ManagedObject*)vm_new_vector_using_vtable_and_thread_pointer(length, vt->clss->get_allocation_handle(),
vm_get_gc_thread_local());    // call gc_alloc
>     ......
>     memcpy(result, h->object, size);   // copy the old object
>     result->set_obj_info(0);                  // obj_info is reset here
>     ......
> }
> I suggest that we'd better modify the original assumption so that VM and GC could manipulate
bits in obj_info they are in charge of without interfering each other.

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