On 6/28/19 6:02 PM, Alberto Garcia wrote: > On Fri 28 Jun 2019 04:57:08 PM CEST, Kevin Wolf wrote: >> Am 28.06.2019 um 16:43 hat Alberto Garcia geschrieben: >>> On Thu 27 Jun 2019 06:05:55 PM CEST, Denis Lunev wrote: >>>> Please note, I am not talking now about your case with COW. Here the >>>> allocation is performed on the sub-cluster basis, i.e. the abscence of >>>> the sub-cluster in the image means hole on that offset. This is >>>> important difference. >>> I mentioned the possibility that if you have a case like 2MB / 64KB >>> and you write to an empty cluster then you could allocate the >>> necessary subclusters, and additionally fallocate() the space of the >>> whole cluster (2MB) in order to try to keep it contiguous. >>> >>> With this we would lose the space saving advantage of having >>> subclusters. But perhaps that would work for smaller cluster sizes >>> (it would mitigate the fragmentation problem). >> There seem to be use cases for both ways. So does this need to be an >> option? > Probably a runtime option, or a heuristic that decides what to do > depending on the cluster size. no, I think that this should be on-disk option as this affects allocation strategy.
Den
