> Then you get very quickly alternating sequences of "L2 depends on > refcount update" (for allocation) and "refcount update depends on L2 > update" (for freeing), which means that Qcow2Cache starts flushing all > the time without accumulating many requests. These are cases that would > benefit as well from the atomicity of journal transactions.
True, Deduplication can hit this case on delete if I remember correctly and it slow down everything. Best regards Benoît