view tests/test-remotefilelog-clone-tree.t @ 42743:8c9a6adec67a

rust-discovery: using the children cache in add_missing

The DAG range computation often needs to get back to very old
revisions, and turns out to be disproportionately long, given
that the end goal is to remove the descendents of the given
missing revisons from the undecided set.

The fast iteration capabilities available in the Rust case make
it possible to avoid the DAG range entirely, at the cost of
precomputing the children cache, and to simply iterate on
children of the given missing revisions.

This is a case where staying on the same side of the interface
between the two languages has clear benefits.

On discoveries with initial undecided sets
small enough to bypass sampling entirely, the total cost of
computing the children cache and the subsequent iteration
becomes better than the Python + C counterpart, which relies on
reachableroots2.

For example, on a repo with more than one million revisions with
an initial undecided set of 11 elements, we get these figures:

Rust version with simple iteration
  addcommons: 57.287us
  first undecided computation: 184.278334ms
  first children cache computation: 131.056us
  addmissings iteration: 42.766us
  first addinfo total: 185.24 ms

Python + C version
  first addcommons: 0.29 ms
  addcommons 0.21 ms
  first undecided computation 191.35 ms
  addmissings 45.75 ms
  first addinfo total: 237.77 ms

On discoveries with large undecided sets, the initial price paid
makes the first addinfo slower than the Python + C version,
but that's more than compensated by the gain in sampling and
subsequent iterations.
Here's an extreme example with an undecided set of a million revisions:

Rust version:
  first undecided computation: 293.842629ms
  first children cache computation: 407.911297ms
  addmissings iteration: 34.312869ms
  first addinfo total: 776.02 ms
  taking initial sample
  query 2: sampling time: 1318.38 ms
  query 2; still undecided: 1005013, sample size is: 200
  addmissings: 143.062us

Python + C version:
  first undecided computation 298.13 ms
  addmissings 80.13 ms
  first addinfo total: 399.62 ms
  taking initial sample
  query 2: sampling time: 3957.23 ms
  query 2; still undecided: 1005013, sample size is: 200
  addmissings 52.88 ms

Differential Revision: https://phab.mercurial-scm.org/D6428

#require no-windows

  $ . "$TESTDIR/remotefilelog-library.sh"

  $ hg init master
  $ cd master
  $ echo treemanifest >> .hg/requires
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > server=True
  > EOF
# uppercase directory name to test encoding
  $ mkdir -p A/B
  $ echo x > A/B/x
  $ hg commit -qAm x

  $ cd ..

# shallow clone from full

  $ hgcloneshallow ssh://user@dummy/master shallow --noupdate
  streaming all changes
  4 files to transfer, 449 bytes of data
  transferred 449 bytes in * seconds (*/sec) (glob)
  searching for changes
  no changes found
  $ cd shallow
  $ cat .hg/requires
  dotencode
  exp-remotefilelog-repo-req-1
  fncache
  generaldelta
  revlogv1
  sparserevlog
  store
  treemanifest
  $ find .hg/store/meta | sort
  .hg/store/meta
  .hg/store/meta/_a
  .hg/store/meta/_a/00manifest.i
  .hg/store/meta/_a/_b
  .hg/store/meta/_a/_b/00manifest.i

  $ hg update
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)

  $ cat A/B/x
  x

  $ ls .hg/store/data
  $ echo foo > A/B/F
  $ hg add A/B/F
  $ hg ci -m 'local content'
  $ ls .hg/store/data
  ca31988f085bfb945cb8115b78fabdee40f741aa

  $ cd ..

# shallow clone from shallow

  $ hgcloneshallow ssh://user@dummy/shallow shallow2  --noupdate
  streaming all changes
  5 files to transfer, 1008 bytes of data
  transferred 1008 bytes in * seconds (*/sec) (glob)
  searching for changes
  no changes found
  $ cd shallow2
  $ cat .hg/requires
  dotencode
  exp-remotefilelog-repo-req-1
  fncache
  generaldelta
  revlogv1
  sparserevlog
  store
  treemanifest
  $ ls .hg/store/data
  ca31988f085bfb945cb8115b78fabdee40f741aa

  $ hg update
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cat A/B/x
  x

  $ cd ..

# full clone from shallow
# - send stderr to /dev/null because the order of stdout/err causes
#   flakiness here
  $ hg clone --noupdate ssh://user@dummy/shallow full 2>/dev/null
  streaming all changes
  remote: abort: Cannot clone from a shallow repo to a full repo.
  [255]

# getbundle full clone

  $ printf '[server]\npreferuncompressed=False\n' >> master/.hg/hgrc
  $ hgcloneshallow ssh://user@dummy/master shallow3
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files
  new changesets 18d955ee7ba0
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ ls shallow3/.hg/store/data
  $ cat shallow3/.hg/requires
  dotencode
  exp-remotefilelog-repo-req-1
  fncache
  generaldelta
  revlogv1
  sparserevlog
  store
  treemanifest