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. Berto
