view tests/test-dirstate-race.t @ 16414:e8d37b78acfb

parsers: use base-16 trie for faster node->rev mapping

This greatly speeds up node->rev lookups, with results that are
often user-perceptible: for instance, "hg --time log" of the node
associated with rev 1000 on a linux-2.6 repo improves from 0.3
seconds to 0.03.  I have not found any instances of slowdowns.

The new perfnodelookup command in contrib/perf.py demonstrates the
speedup more dramatically, since it performs no I/O.  For a single
lookup, the new code is about 40x faster.

These changes also prepare the ground for the possibility of further
improving the performance of prefix-based node lookups.

  $ hg init
  $ echo a > a
  $ hg add a
  $ hg commit -m test

Do we ever miss a sub-second change?:

  $ for i in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20; do
  >     hg co -qC 0
  >     echo b > a
  >     hg st
  > done
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a