Eric Wong <e@xxxxxxxxx> writes: > With many alternates, the duplicate check in alt_odb_usable() > wastes many cycles doing repeated fspathcmp() on every existing > alternate. Use a khash to speed up lookups by odb->path. > > Since the kh_put_* API uses the supplied key without > duplicating it, we also take advantage of it to replace both > xstrdup() and strbuf_release() in link_alt_odb_entry() with > strbuf_detach() to avoid the allocation and copy. > > In a test repository with 50K alternates and each of those 50K > alternates having one alternate each (for a total of 100K total > alternates); this speeds up lookup of a non-existent blob from > over 16 minutes to roughly 2.7 seconds on my busy workstation. > > Note: all underlying git object directories were small and > unpacked with only loose objects and no packs. Having to load > packs increases times significantly. > > v3: Introduce and use fspatheq and fspathhash functions; > avoid unnecessary checks for allocation failures already > handled by our own *alloc wrappers. The last one does not belong to the commit log message, as "git log" readers do not care about and will not have access to v2 and earlier.
