On Tue, 15 Apr 2025 at 19:22, Andreas Dilger <adilger@xxxxxxxxx> wrote: > If the negative dentry count exceeds the actual entry count, it would > be more efficient to just cache all of the positive dentries and mark > the directory with a "full dentry list" flag that indicates all of the > names are already present in dcache and any miss is authoritative. > In essence that gives an "infinite" negative lookup cache instead of > explicitly storing all of the possible negative entries. This sounds nice in theory, but there are quite a number of things to sort out: - The "full dir read" needs to be done in the background to avoid large latencies, right? - Instantiate inodes during this, or have some dentry flag indicating that it's to be done later? - When does the whole directory get reclaimed? - What about revalidation in netfs? How often should a "full dir read" get triggered? I feel that it's just too complex. What's wrong with just trying to get rid of the bad effects of negative dentries, instead of getting rid of the dentries themselves ? Lack of memory pressure should mean that nobody else needs that memory, so it should make no difference if it's used up in negative dentries instead of being free memory. Maybe I'm missing something fundamental? Thanks, Miklos
