Ganesh Sittampalam <[email protected]> writes: >> Actually, the compatible change that removes the common prefix of zeroes >> could already help with the problem. > > That's a good point actually, is removing the prefix really backwards > compatible? Old darcs binaries won't be able to read the unprefixed files, > will > they? Actually, they will -- pre-2.0 darcs used to write those, even. The prefixes were added quite late in the 2.0 development to aid diffing performance (the mtime optimisation issue). I think darcs only cares that the hash has one of the lengths it knows, sha1, sha256 or sha256+size prefix. I definitely can read prefix-less repositories with old darcs just fine.
Unfortunately, we have found out yesterday that this doesn't help at all. It seems that lookup performance is rather sensitive to lookup order, but with random access, these two give roughly the same performance. For directory order, the prefixed variation is faster by around factor of 2, but I cannot reproduce the ordering easily for a non-prefixed list. Anyway, there's something fishy about the implementation of ext3/vfs lookups in Linux... (You'd expect that evenly distributed directory list would perform no worse -- or actually better -- than a very poorly distributed one -- even git makes that assumption in its format.) Yours, Petr. _______________________________________________ darcs-users mailing list [email protected] http://lists.osuosl.org/mailman/listinfo/darcs-users
