EXT4 Getting Faster Case-Insensitive Performance

The Linux 5.2 kernel brings optional per-directory case-insensitive filenames/folders while with the Linux 5.3 kernel that new EXT4 feature will see better performance.

The EXT4 case-insensitive support relies upon Unicode case handling and preserves the actual case of the directory/files on-disk. It's the look-up process for checking for case-insensitive matches that is being made faster in the latest EXT4 code ahead of Linux 5.3.

Gabriel Krisman Bertazi of Collabora who worked on this original EXT4 case-insensitive feature has provided this new optimization. The optimization is a temporary cache to handle the case-folded version of the file-names under lookup. By eliminating the repetitive case-folding, Gabriel saw around a 30% speed-up on large directories. But the amount of files in the directory and length of file-name can also change for the impact of this optimization currently queued in the EXT4 dev branch ahead of Linux 5.3.

For those that missed it, Wine-Staging 4.10 added EXT4 case-insensitive support as an optional feature alternative to Wine's old file case handling functionality.