Commit 3aa9b35f authored by Ömer Sinan Ağacan's avatar Ömer Sinan Ağacan Committed by Marge Bot

Zero any slop after compaction in compacting GC

In copying GC, with the relevant debug flags enabled, we release the old
blocks after a GC, and the block allocator zeroes the space before
releasing a block. This effectively zeros the old heap.

In compacting GC we reuse the blocks and previously we didn't zero the
unused space in a compacting generation after compaction. With this
patch we zero the slop between the free pointer and the end of the block
when we're done with compaction and when switching to a new block
(because the current block doesn't have enough space for the next object
we're shifting).
parent c61b9b02
Pipeline #16595 passed with stages
in 364 minutes
......@@ -829,18 +829,27 @@ update_bkwd_compact( generation *gen )
for (; bd != NULL; bd = bd->link) {
P_ p = bd->start;
while (p < bd->free ) {
while (p < bd->free) {
while ( p < bd->free && !is_marked(p,bd) ) {
while (p < bd->free && !is_marked(p,bd)) {
if (p >= bd->free) {
if (is_marked(p+1,bd)) {
// don't forget to update the free ptr in the block desc.
// Don't forget to update the free ptr in the block desc
free_bd->free = free;
// Zero the remaining bytes of this block before moving on to
// the next block
IF_DEBUG(zero_on_gc, {
memset(free_bd->free, 0xaa,
BLOCK_SIZE - ((W_)(free_bd->free - free_bd->start) * sizeof(W_)));
free_bd = free_bd->link;
free = free_bd->start;
......@@ -867,13 +876,21 @@ update_bkwd_compact( generation *gen )
// free the remaining blocks and count what's left.
// Free the remaining blocks and count what's left.
free_bd->free = free;
if (free_bd->link != NULL) {
free_bd->link = NULL;
// Zero the free bits of the last used block.
IF_DEBUG(zero_on_gc, {
W_ block_size_bytes = free_bd->blocks * BLOCK_SIZE;
W_ block_in_use_bytes = (free_bd->free - free_bd->start) * sizeof(W_);
W_ block_free_bytes = block_size_bytes - block_in_use_bytes;
memset(free_bd->free, 0xaa, block_free_bytes);
return free_blocks;
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