view tests/test-sparse-revlog.t @ 44386:8f7c6656ac79

rust-nodemap: pure Rust example

To run, use `cargo run --release --example nodemap`

This demonstrates that simple scenarios entirely written
in Rust can content themselves with `NodeTree<T>`.

The example mmaps both the nodemap file and the changelog index.
We had of course to include an implementation of `RevlogIndex`
directly, which isn't much at this stage. It felt a bit
prematurate to include it in the lib.

Here are some first performance measurements, obtained with
this example, on a clone of mozilla-central with 440000
changesets:

  (create) Nodemap constructed in RAM in 153.638305ms
  (query CAE63161B68962) found in 22.362us: Ok(Some(269489))
  (bench) Did 3 queries in 36.418µs (mean 12.139µs)
  (bench) Did 50 queries in 184.318µs (mean 3.686µs)
  (bench) Did 100000 queries in 31.053461ms (mean 310ns)

To be fair, even between bench runs, results tend to depend whether
the file is still in kernel caches, and it's not so easy to
get back to a real cold start. The worst we've seen was in the
50us ballpark.

In any busy server setting, the pages would always be in RAM.

We hope it's good enough not to be significantly slower on any
concrete Mercurial operation than the C nodetree when fully in RAM,
and of course this implementation has the serious headstart advantage
of persistence.

Differential Revision: https://phab.mercurial-scm.org/D7797

====================================
Test delta choice with sparse revlog
====================================

Sparse-revlog usually shows the most gain on Manifest. However, it is simpler
to general an appropriate file, so we test with a single file instead. The
goal is to observe intermediate snapshot being created.

We need a large enough file. Part of the content needs to be replaced
repeatedly while some of it changes rarely.

  $ bundlepath="$TESTDIR/artifacts/cache/big-file-churn.hg"

  $ expectedhash=`cat "$bundlepath".md5`

#if slow

  $ if [ ! -f "$bundlepath" ]; then
  >     "$TESTDIR"/artifacts/scripts/generate-churning-bundle.py > /dev/null
  > fi

#else

  $ if [ ! -f "$bundlepath" ]; then
  >     echo 'skipped: missing artifact, run "'"$TESTDIR"'/artifacts/scripts/generate-churning-bundle.py"'
  >     exit 80
  > fi

#endif

  $ currenthash=`f -M "$bundlepath" | cut -d = -f 2`
  $ if [ "$currenthash" != "$expectedhash" ]; then
  >     echo 'skipped: outdated artifact, md5 "'"$currenthash"'" expected "'"$expectedhash"'" run "'"$TESTDIR"'/artifacts/scripts/generate-churning-bundle.py"'
  >     exit 80
  > fi

  $ cat >> $HGRCPATH << EOF
  > [format]
  > sparse-revlog = yes
  > maxchainlen = 15
  > [storage]
  > revlog.optimize-delta-parent-choice = yes
  > revlog.reuse-external-delta = no
  > EOF
  $ hg init sparse-repo
  $ cd sparse-repo
  $ hg unbundle $bundlepath
  adding changesets
  adding manifests
  adding file changes
  added 5001 changesets with 5001 changes to 1 files (+89 heads)
  new changesets 9706f5af64f4:d9032adc8114 (5001 drafts)
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg up
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  updated to "d9032adc8114: commit #5000"
  89 other heads for branch "default"

  $ hg log --stat -r 0:3
  changeset:   0:9706f5af64f4
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     initial commit
  
   SPARSE-REVLOG-TEST-FILE |  10500 ++++++++++++++++++++++++++++++++++++++++++++++
   1 files changed, 10500 insertions(+), 0 deletions(-)
  
  changeset:   1:724907deaa5e
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     commit #1
  
   SPARSE-REVLOG-TEST-FILE |  1068 +++++++++++++++++++++++-----------------------
   1 files changed, 534 insertions(+), 534 deletions(-)
  
  changeset:   2:62c41bce3e5d
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     commit #2
  
   SPARSE-REVLOG-TEST-FILE |  1068 +++++++++++++++++++++++-----------------------
   1 files changed, 534 insertions(+), 534 deletions(-)
  
  changeset:   3:348a9cbd6959
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     commit #3
  
   SPARSE-REVLOG-TEST-FILE |  1068 +++++++++++++++++++++++-----------------------
   1 files changed, 534 insertions(+), 534 deletions(-)
  

  $ f -s .hg/store/data/*.d
  .hg/store/data/_s_p_a_r_s_e-_r_e_v_l_o_g-_t_e_s_t-_f_i_l_e.d: size=63327412
  $ hg debugrevlog *
  format : 1
  flags  : generaldelta
  
  revisions     :     5001
      merges    :      625 (12.50%)
      normal    :     4376 (87.50%)
  revisions     :     5001
      empty     :        0 ( 0.00%)
                     text  :        0 (100.00%)
                     delta :        0 (100.00%)
      snapshot  :      383 ( 7.66%)
        lvl-0   :              3 ( 0.06%)
        lvl-1   :             20 ( 0.40%)
        lvl-2   :             68 ( 1.36%)
        lvl-3   :            112 ( 2.24%)
        lvl-4   :            180 ( 3.60%)
      deltas    :     4618 (92.34%)
  revision size : 63327412
      snapshot  :  9886710 (15.61%)
        lvl-0   :         603104 ( 0.95%)
        lvl-1   :        1559991 ( 2.46%)
        lvl-2   :        2295592 ( 3.62%)
        lvl-3   :        2531199 ( 4.00%)
        lvl-4   :        2896824 ( 4.57%)
      deltas    : 53440702 (84.39%)
  
  chunks        :     5001
      0x78 (x)  :     5001 (100.00%)
  chunks size   : 63327412
      0x78 (x)  : 63327412 (100.00%)
  
  avg chain length  :        9
  max chain length  :       15
  max chain reach   : 28248745
  compression ratio :       27
  
  uncompressed data size (min/max/avg) : 346468 / 346472 / 346471
  full revision size (min/max/avg)     : 201008 / 201050 / 201034
  inter-snapshot size (min/max/avg)    : 11596 / 168150 / 24430
      level-1   (min/max/avg)          : 16653 / 168150 / 77999
      level-2   (min/max/avg)          : 12951 / 85595 / 33758
      level-3   (min/max/avg)          : 11608 / 43029 / 22599
      level-4   (min/max/avg)          : 11596 / 21632 / 16093
  delta size (min/max/avg)             : 10649 / 107163 / 11572
  
  deltas against prev  : 3910 (84.67%)
      where prev = p1  : 3910     (100.00%)
      where prev = p2  :    0     ( 0.00%)
      other            :    0     ( 0.00%)
  deltas against p1    :  648 (14.03%)
  deltas against p2    :   60 ( 1.30%)
  deltas against other :    0 ( 0.00%)