parsers: incrementally parse the revlog index in C...
parsers: incrementally parse the revlog index in C
We only parse entries in a revlog index file when they are actually
needed, and cache them when first requested.
This makes a huge difference to performance on large revlogs when
accessing the tip revision or performing a handful of numeric lookups
(very common cases). For instance, "hg --time tip --template {node}"
on a tree with 300,000 revs takes 0.15 before, 0.02 after.
Even for revlog-intensive operations (e.g. running "hg log" to
completion), the lazy approach is about 1% faster than the eager
parse_index2.