Am 28.06.2019 um 17:02 hat Alberto Garcia geschrieben: > 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.
How would the heuristic decide whether the user wants to save disk space or whether they consider avoiding fragmentation (i.e. performance) more important? Kevin
