DAOS-16818 common: Evict NE memory bucket when empty - MD_ON_SSD_p2

Inorder to ensure that gc happens in an incremental fashion, garbage
reclaim is triggerred not only when number of empty buckets is greater
than threshold but also when free space in general has increased by a
threshhold.

Signed-off-by: Sherin T George <[email protected]>

src/common/dav_v2/heap.c

@@ -2297,19 +2297,33 @@ heap_force_recycle(struct palloc_heap *heap)
 	struct bucket *defb;
 	struct mbrt   *mb;
 	uint32_t       zone_id;
-
-	if (heap->rt->empty_nemb_cnt < heap->rt->empty_nemb_gcth)
-		return 0;
+	uint32_t       max_reclaim = heap->rt->empty_nemb_gcth * 2;
 
 	mb   = heap_mbrt_get_mb(heap, 0);
+
+	if (heap->rt->empty_nemb_cnt < heap->rt->empty_nemb_gcth) {
+		if ((mb->space_usage > mb->prev_usage) ||
+		    ((mb->prev_usage - mb->space_usage) <
+		     (ZONE_MAX_SIZE * heap->rt->empty_nemb_gcth))) {
+			if (mb->space_usage > mb->prev_usage)
+				mb->prev_usage = mb->space_usage;
+			return 0;
+		}
+	}
+
+
 	defb = mbrt_bucket_acquire(mb, DEFAULT_ALLOC_CLASS_ID);
 	while (heap_reclaim_next_ne(heap, &zone_id) == 0) {
 		heap_reclaim_zone_garbage(heap, defb, zone_id);
 		heap_reclaim_setlast_ne(heap, zone_id);
+		if (--max_reclaim == 0)
+			break;
 	}
+
 	heap_reclaim_garbage(heap, defb);
 	mbrt_bucket_release(defb);
 	heap_populate_nemb_unused(heap);
+	mb->prev_usage = mb->space_usage;
 
 	if (heap->rt->empty_nemb_cnt >= heap->rt->empty_nemb_gcth)
 		D_ERROR("Force GC failed to free up enough nembs, cnt = %d",