+ int mark; // mark (not copy)? (old gen only)
+ int compact; // compact (not sweep)? (old gen only)
+
+ bdescr * old_blocks; // bdescr of first from-space block
+ unsigned int n_old_blocks; // number of blocks in from-space
+ unsigned int live_estimate; // for sweeping: estimate of live data
+
+ bdescr * todos; // blocks waiting to be scavenged
+ bdescr * todos_last;
+ unsigned int n_todos; // count of above
+
+ bdescr * part_blocks; // partially-full scanned blocks
+ unsigned int n_part_blocks; // count of above
+