2011/9/14 Kevin Wolf <kw...@redhat.com>: ... > >>>>> But let's measure the effects first, I suspect that for cluster >>>>> allocation it doesn't help much because every REF- comes with a REF+. >>>>> >>>> >>>> That's 50% of effort if REF- clusters are far from REF+ :) >>> >>> I would expect that the next REF+ allocates exactly the REF- cluster. >>> But you still have a point, we save the write on REF- and combine it >>> with the REF+ write. >>> >> >> This is still a TODO for REF+ patch. > > Actually, I was talking about the qcow2_cache_entry_mark_dirty_wb() case > without any other change. You get it automatically then. >
No, I forgot I already thought about this. REF- cluster get not reused on normal operation, but reach 0 only during snapshot delete. This cause if it reach 0 it means that it was 1 but if it was 1 copied flag would be 1 and so there is no reason to decrement counter (reductio ab asburdum). Frediano
