parsers: when available, use a presized dictionary for the file foldmap On a repo with over 300,000 files, this speeds up perffilefoldmap: before: wall 0.178421 comb 0.180000 user 0.160000 sys 0.020000 (best of 55) after: wall 0.164462 comb 0.160000 user 0.140000 sys 0.020000 (best of 59)