"The main issue from the post is quite simple: if you allocate a lot of small objects, D runtime will place them inside chunks (called pools) of fixed size (like 4 MB) that it requested from the OS. Each time a pool is filled up it will do a GC cycle and only if there's still no room for new object it will allocate a new pool. That means number of GC cycles in this situation is proportional to number of objects you allocate, while each GC cycle time is proportional to the managed heap size. It leads to quadratic complexity and awful slowness. If runtime allocated pools not of fixed size but adapted their size to the allocation rate, this scenario could be significantly faster."
"The main issue from the post is quite simple: if you allocate a lot of small objects, D runtime will place them inside chunks (called pools) of fixed size (like 4 MB) that it requested from the OS. Each time a pool is filled up it will do a GC cycle and only if there's still no room for new object it will allocate a new pool. That means number of GC cycles in this situation is proportional to number of objects you allocate, while each GC cycle time is proportional to the managed heap size. It leads to quadratic complexity and awful slowness. If runtime allocated pools not of fixed size but adapted their size to the allocation rate, this scenario could be significantly faster."