cardTableExtension.cpp revision 113
/*
* Copyright 2001-2006 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*
*/
# include "incls/_precompiled.incl"
# include "incls/_cardTableExtension.cpp.incl"
// Checks an individual oop for missing precise marks. Mark
// may be either dirty or newgen.
class CheckForUnmarkedOops : public OopClosure {
private:
protected:
template <class T> void do_oop_work(T* p) {
!_card_table->addr_is_marked_imprecise(p)) {
// Don't overwrite the first missing card mark
if (_unmarked_addr == NULL) {
_unmarked_addr = (HeapWord*)p;
}
}
}
public:
bool has_unmarked_oop() {
return _unmarked_addr != NULL;
}
};
// Checks all objects for the existance of some type of mark,
// precise or imprecise, dirty or newgen.
class CheckForUnmarkedObjects : public ObjectClosure {
private:
public:
// No point in asserting barrier set type here. Need to make CardTableExtension
// a unique barrier set type.
}
// Card marks are not precise. The current system can leave us with
// a mismash of precise marks and begining of object marks. This means
// we test for missing precise marks first. If any are found, we don't
// fail unless the object head is also unmarked.
if (object_check.has_unmarked_oop()) {
}
}
};
// Checks for precise marking of oops as newgen.
class CheckForPreciseMarks : public OopClosure {
private:
protected:
template <class T> void do_oop_work(T* p) {
}
}
public:
};
// We get passed the space_top value to prevent us from traversing into
// the old_gen promotion labs, which cannot be safely parsed.
{
"ObjectStartArray does not cover space");
// scan card marking array
while (current_card <= end_card) {
// skip clean cards
if (card_is_clean(value)) {
current_card++;
} else {
// we found a non-clean card
// find object starting on card
// bottom_obj = (oop*)start_array->object_start((HeapWord*)bottom);
// make sure we don't scan oops we already looked at
// figure out when to stop scanning
bool restart_scanning;
do {
restart_scanning = false;
// find a clean card
while (current_card <= end_card) {
value = *current_card;
if (card_is_clean(value)) break;
current_card++;
}
// check if we reached the end, if so we are done
if (current_card >= end_card) {
current_card++;
} else {
// we have a clean card, find object starting on that card
// top_obj = (oop*)start_array->object_start((HeapWord*)top);
// an arrayOop is starting on the clean card - since we do exact store
// checks for objArrays we are done
} else {
// otherwise, it is possible that the object starting on the clean card
// spans the entire card, and that the store happened on a later card.
// figure out where the object ends
if (top_card > first_clean_card) {
// object ends a different card
if (card_is_clean(*top_card)) {
// the ending card is clean, we are done
} else {
// the ending card is not clean, continue scanning at start of do-while
restart_scanning = true;
}
} else {
// object ends on the clean card, we are done.
}
}
}
} while (restart_scanning);
// we know which cards to scan, now clear them
while (first_nonclean_card < first_clean_card) {
}
// scan oops in objects
// hoisted the if (depth_first) check out of the loop
if (depth_first){
do {
} while (bottom_obj < top);
} else {
do {
} while (bottom_obj < top);
}
// remember top oop* scanned
}
}
}
}
int dirty_card_count = 0;
if (worker_start_card >= end_card)
return; // We're done.
if (worker_end_card > end_card)
// We do not want to scan objects more than once. In order to accomplish
// this, we assert that any object with an object head inside our 'slice'
// belongs to us. We may need to extend the range of scanned cards if the
// last object continues into the next 'slice'.
//
// Note! ending cards are exclusive!
// If there are not objects starting within the chunk, skip it.
continue;
}
// Update our begining addr
if (first_object < slice_start) {
}
// Update the ending addr
// The subtraction is important! An object may start precisely at slice_end.
// worker_end_card is exclusive, so bump it one past the end of last_object's
// covered span.
if (worker_end_card > end_card)
}
// Note that worker_start_card >= worker_end_card is legal, and happens when
// an object spans an entire slice.
while (current_card < worker_end_card) {
// Find an unclean card.
current_card++;
}
// Find the end of a run of contiguous unclean cards
current_card++;
}
if (current_card < worker_end_card) {
// Some objects may be large enough to span several cards. If such
// an object has more than one dirty card, separated by a clean card,
// we will attempt to scan it twice. The test against "last_scanned"
// prevents the redundant object scan, but it does not prevent newly
// marked cards from being cleaned.
assert(ending_card_of_last_object <= worker_end_card, "ending_card_of_last_object is greater than worker_end_card");
if (ending_card_of_last_object > current_card) {
// This means the object spans the next complete card.
// We need to bump the current_card to ending_card_of_last_object
}
}
}
if (first_unclean_card < worker_end_card) {
// "p" should always be >= "last_scanned" because newly GC dirtied
// cards are no longer scanned again (see comment at end
// of loop on the increment of "current_card"). Test that
// hypothesis before removing this code.
// If this code is removed, deal with the first time through
// the loop when the last_scanned is the object starting in
// the previous slice.
assert((p >= last_scanned) ||
"Should no longer be possible");
if (p < last_scanned) {
// Avoid scanning more than once; this can happen because
// newgen cards set by GC may a different set than the
// originally dirty set
p = last_scanned;
}
// Test slice_end first!
}
// we know which cards to scan, now clear them
while (first_unclean_card < following_clean_card) {
*first_unclean_card++ = clean_card;
}
const int interval = PrefetchScanIntervalInBytes;
// scan all objects in the range
if (interval != 0) {
// hoisted the if (depth_first) check out of the loop
if (depth_first) {
while (p < to) {
m->push_contents(pm);
p += m->size();
}
} else {
while (p < to) {
m->copy_contents(pm);
p += m->size();
}
}
} else {
// hoisted the if (depth_first) check out of the loop
if (depth_first) {
while (p < to) {
m->push_contents(pm);
p += m->size();
}
} else {
while (p < to) {
m->copy_contents(pm);
p += m->size();
}
}
}
last_scanned = p;
}
// "current_card" is still the "following_clean_card" or
// the current_card is >= the worker_end_card so the
// loop will not execute again.
(current_card >= worker_end_card),
"current_card should only be incremented if it still equals "
"following_clean_card");
// Increment current_card so that it is not processed again.
// It may now be dirty because a old-to-young pointer was
// found on it an updated. If it is now dirty, it cannot be
// be safely cleaned in the next iteration.
current_card++;
}
}
}
// This should be called before a scavenge.
}
// This should be called immediately after a scavenge, before mutators resume.
}
// FIX ME ASSERT HERE
if (*bot == verify_card)
*bot = youngergen_card;
bot++;
}
}
if (card_is_dirty(val))
return true;
if (card_is_newgen(val))
return true;
if (card_is_clean(val))
return false;
assert(false, "Found unhandled card mark type");
return false;
}
// Also includes verify_card
if (card_is_newgen(val))
return true;
if (card_is_verify(val))
return true;
if (card_is_clean(val))
return false;
if (card_is_dirty(val))
return false;
assert(false, "Found unhandled card mark type");
return false;
}
// Assumes that only the base or the end changes. This allows indentification
// of the region that is being resized. The
// CardTableModRefBS::resize_covered_region() is used for the normal case
// where the covered regions are growing or shrinking at the high end.
// The method resize_covered_region_by_end() is analogous to
// CardTableModRefBS::resize_covered_region() but
// for regions that grow or shrink at the low end.
for (int i = 0; i < _cur_covered_regions; i++) {
// Found a covered region with the same start as the
// new region. The region is growing or shrinking
// from the start of the region.
return;
}
break;
}
}
int changed_region = -1;
for (int j = 0; j < _cur_covered_regions; j++) {
changed_region = j;
// This is a case where the covered region is growing or shrinking
// at the start of the region.
"The sizes should be different here");
return;
}
}
// This should only be a new covered region (where no existing
// covered region matches at the start or the end).
"An existing region should have been found");
}
}
"Only expect an expansion at the low end at a GC");
#ifdef ASSERT
for (int k = 0; k < _cur_covered_regions; k++) {
break;
}
}
#endif
// Commit new or uncommit old pages, if necessary.
// Update card table entries
// Set the new start of the committed region
// Update the covered region
if (TraceCardTableModRefBS) {
int ind = changed_region;
" _covered[%d].start(): " INTPTR_FORMAT
" _covered[%d].last(): " INTPTR_FORMAT,
" _committed[%d].start(): " INTPTR_FORMAT
" _committed[%d].last(): " INTPTR_FORMAT,
" byte_for(start): " INTPTR_FORMAT
" byte_for(last): " INTPTR_FORMAT,
" addr_for(start): " INTPTR_FORMAT
" addr_for(last): " INTPTR_FORMAT,
}
}
// Commit new or uncommit old pages, if necessary.
"The ends of the regions are expected to match");
// Extend the start of this _committed region to
// to cover the start of any previous _committed region.
// This forms overlapping regions, but never interior regions.
// Only really need to set start of "cur_committed" to
// the new start (min_prev_start) but assertion checking code
// below use cur_committed.end() so make it correct.
}
#ifdef ASSERT
os::vm_page_size()),
"Starts should have proper alignment");
#endif
// Round down because this is for the start address
// The guard page is always committed and should not be committed over.
// This method is used in cases where the generation is growing toward
// lower addresses but the guard region is still at the end of the
// card table. That still makes sense when looking for writes
// off the end of the card table.
// Expand the committed region
//
// Case A
// |+ guard +|
// |+ cur committed +++++++++|
// |+ new committed +++++++++++++++++|
//
// Case B
// |+ guard +|
// |+ cur committed +|
// |+ new committed +++++++|
//
// These are not expected because the calculation of the
// cur committed region and the new committed region
// share the same end for the covered region.
// Case C
// |+ guard +|
// |+ cur committed +|
// |+ new committed +++++++++++++++++|
// Case D
// |+ guard +|
// |+ cur committed +++++++++++|
// |+ new committed +++++++|
if(!new_committed.is_empty()) {
new_committed.byte_size())) {
"card table expansion");
}
}
// Shrink the committed region
if (!uncommit_region.is_empty()) {
uncommit_region.byte_size())) {
"card table contraction");
}
}
}
"end should not change");
}
// Set the new start of the committed region
os::vm_page_size());
}
// Initialize the card entries. Only consider the
// region covered by the card table (_whole_heap)
} else {
}
// If _whole_heap starts at the original covered regions start,
// this loop will not execute.
}
// Update the covered region
// reorder regions. There should only be at most 1 out
// of order.
for (int i = _cur_covered_regions-1 ; i > 0; i--) {
_covered[i] = covered_mr;
_committed[i] = committed_mr;
break;
}
}
#ifdef ASSERT
for (int m = 0; m < _cur_covered_regions-1; m++) {
"Covered regions out of order");
"Committed regions out of order");
}
#endif
}
// Returns the start of any committed region that is lower than
// the target committed region (index ind) and that intersects the
// target region. If none, return start of target region.
//
// -------------
// | |
// -------------
// ------------
// | target |
// ------------
// -------------
// | |
// -------------
// ^ returns this
//
// -------------
// | |
// -------------
// ------------
// | target |
// ------------
// -------------
// | |
// -------------
// ^ returns this
for (int j = 0; j < ind; j++) {
if ((this_start < min_start) &&
}
}
return min_start;
}