view tests/test-hgk.t @ 34880:9e18ab7f7240

sparse-read: move from a recursive-based approach to a heap-based one

The previous recursive approach was trying to optimise each read slice to have
a good density. It had the tendency to over-optimize smaller slices while
leaving larger hole in others.

The new approach focuses on improving the combined density of all the reads,
instead of the individual slices. It slices at the largest gaps first, as they
reduce the total amount of read data the most efficiently.

Another benefit of this approach is that we iterate over the delta chain only
once, reducing the overhead of slicing long delta chains.

On the repository we use for tests, the new approach shows similar or faster
performance than the current default linear full read.

The repository contains about 450,000 revisions with many concurrent
topological branches. Tests have been run on two versions of the repository:
one built with the current delta constraint, and the other with an unlimited
delta span (using 'experimental.maxdeltachainspan=0')

Below are timings for building 1% of all the revision in the manifest log using
'hg perfrevlogrevisions -m'. Times are given in seconds. They include the new
couple of follow-up changeset in this series.

delta-span  standard    unlimited
linear-read     922s         632s
sparse-read     814s         566s

Minimal hgk check

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "hgk=" >> $HGRCPATH
  $ hg init repo
  $ cd repo
  $ echo a > a
  $ hg ci -Am adda
  adding a
  $ hg debug-cat-file commit 0
  tree a0c8bcbbb45c
  parent 000000000000
  author test 0 0
  revision 0
  branch default
  phase draft
  
  adda
  $ echo b > b
  $ hg ci -Am addb
  adding b
  $ hg log -T '{node}\n'
  102a90ea7b4a3361e4082ed620918c261189a36a
  07f4944404050f47db2e5c5071e0e84e7a27bba9

  $ hg debug-diff-tree 07f494440405 102a90ea7b4a
  :000000 100664 000000000000 1e88685f5dde N	b	b
  $ hg debug-diff-tree 07f494440405 102a90ea7b4a --patch
  diff --git a/b b/b
  new file mode 100644
  --- /dev/null
  +++ b/b
  @@ -0,0 +1,1 @@
  +b

Ensure that diff-tree output isn't affected by diffopts
  $ hg --config diff.noprefix=True debug-diff-tree 07f494440405 102a90ea7b4a
  :000000 100664 000000000000 1e88685f5dde N	b	b
  $ hg --config diff.noprefix=True debug-diff-tree --patch 07f494440405 102a90ea7b4a
  diff --git a/b b/b
  new file mode 100644
  --- /dev/null
  +++ b/b
  @@ -0,0 +1,1 @@
  +b

  $ cd ..