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7039089: G1: changeset for 7037276 broke heap verification, and related cleanups

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In G1 heap verification, we no longer scan perm to G1-collected heap refs as part of process_strong_roots() but rather in a separate explicit oop iteration over the perm gen. This preserves the original perm card-marks. Added a new assertion in younger_refs_iterate() to catch a simple subcase where the user may have forgotten a prior save_marks() call, as happened in the case of G1's attempt to iterate perm to G1 refs when verifying the heap before exit. The assert was deliberately weakened for ParNew+CMS and will be fixed for that combination in a future CR. Also made some (non-G1) cleanups related to code and comments obsoleted by the migration of Symbols to the native heap.

Reviewed-by: iveresov, jmasa, tonyp
This commit is contained in:
Y. Srinivas Ramakrishna 2011-04-26 21:17:24 -07:00
parent e3121a5a43
commit d86311b13c
8 changed files with 69 additions and 28 deletions
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29
hotspot/src/share/vm/memory/cardTableRS.cpp
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@ -250,7 +250,34 @@ void CardTableRS::younger_refs_in_space_iterate(Space* sp,
cl->gen_boundary());
ClearNoncleanCardWrapper clear_cl(dcto_cl, this);
_ct_bs->non_clean_card_iterate_possibly_parallel(sp, sp->used_region_at_save_marks(),
const MemRegion urasm = sp->used_region_at_save_marks();
#ifdef ASSERT
// Convert the assertion check to a warning if we are running
// CMS+ParNew until related bug is fixed.
MemRegion ur = sp->used_region();
assert(ur.contains(urasm) || (UseConcMarkSweepGC && UseParNewGC),
err_msg("Did you forget to call save_marks()? "
"[" PTR_FORMAT ", " PTR_FORMAT ") is not contained in "
"[" PTR_FORMAT ", " PTR_FORMAT ")",
urasm.start(), urasm.end(), ur.start(), ur.end()));
// In the case of CMS+ParNew, issue a warning
if (!ur.contains(urasm)) {
assert(UseConcMarkSweepGC && UseParNewGC, "Tautology: see assert above");
warning("CMS+ParNew: Did you forget to call save_marks()? "
"[" PTR_FORMAT ", " PTR_FORMAT ") is not contained in "
"[" PTR_FORMAT ", " PTR_FORMAT ")",
urasm.start(), urasm.end(), ur.start(), ur.end());
MemRegion ur2 = sp->used_region();
MemRegion urasm2 = sp->used_region_at_save_marks();
if (!ur.equals(ur2)) {
warning("CMS+ParNew: Flickering used_region()!!");
}
if (!urasm.equals(urasm2)) {
warning("CMS+ParNew: Flickering used_region_at_save_marks()!!");
}
}
#endif
_ct_bs->non_clean_card_iterate_possibly_parallel(sp, urasm,
dcto_cl, &clear_cl);
}