-must be a multiple of the alignment. We assume that 8192 is going to be
-suitably aligned. */
-
-#define STORE_BLOCK_SIZE (8192 - ALIGNED_SIZEOF_STOREBLOCK)
+must be a multiple of the alignment. We assume that 4096 is going to be
+suitably aligned. Double the size per-pool for every malloc, to mitigate
+certain denial-of-service attacks. Don't bother to decrease on block frees.
+We waste average half the current alloc size per pool. This could be several
+hundred kB now, vs. 4kB with a constant-size block size. But the search time
+for is_tainted(), linear in the number of blocks for the pool, is O(n log n)
+rather than O(n^2).
+A test of 2000 RCPTs and just accept ACL had 370kB in 21 blocks before,
+504kB in 6 blocks now, for the untainted-main (largest) pool.
+Builds for restricted-memory system can disable the expansion by
+defining RESTRICTED_MEMORY */
+/*XXX should we allow any for malloc's own overhead? But how much? */
+
+/* #define RESTRICTED_MEMORY */
+#define STORE_BLOCK_SIZE(order) ((1U << (order)) - ALIGNED_SIZEOF_STOREBLOCK)