view tests/test-sparse-clone.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

test sparse

  $ cat >> $HGRCPATH << EOF
  > [ui]
  > ssh = python "$RUNTESTDIR/dummyssh"
  > username = nobody <[e-mail]>
  > [extensions]
  > sparse=
  > purge=
  > strip=
  > rebase=
  > EOF

  $ hg init myrepo
  $ cd myrepo
  $ echo a > index.html
  $ echo x > data.py
  $ echo z > readme.txt
  $ cat > webpage.sparse <<EOF
  > [include]
  > *.html
  > EOF
  $ cat > backend.sparse <<EOF
  > [include]
  > *.py
  > EOF
  $ hg ci -Aqm 'initial'
  $ cd ..

Verify local clone with a sparse profile works

  $ hg clone --enable-profile webpage.sparse myrepo clone1
  updating to branch default
  warning: sparse profile 'webpage.sparse' not found in rev 000000000000 - ignoring it
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd clone1
  $ ls
  index.html
  $ cd ..

Verify local clone with include works

  $ hg clone --include *.sparse myrepo clone2
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd clone2
  $ ls
  backend.sparse
  webpage.sparse
  $ cd ..

Verify local clone with exclude works

  $ hg clone --exclude data.py myrepo clone3
  updating to branch default
  4 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd clone3
  $ ls
  backend.sparse
  index.html
  readme.txt
  webpage.sparse
  $ cd ..

Verify sparse clone profile over ssh works

  $ hg clone -q --enable-profile webpage.sparse ssh://user@dummy/myrepo clone4
  warning: sparse profile 'webpage.sparse' not found in rev 000000000000 - ignoring it
  $ cd clone4
  $ ls
  index.html
  $ cd ..