view tests/test-narrow-trackedcmd.t @ 51681:522b4d729e89

mmap: populate the mapping by default

Without pre-population, accessing all data through a mmap can result in many
pagefault, reducing performance significantly. If the mmap is prepopulated, the
performance can no longer get slower than a full read.
(See benchmark number below)

In some cases were very few data is read, prepopulating can be overkill and
slower than populating on access (through page fault). So that behavior can be
controlled when the caller can pre-determine the best behavior.
(See benchmark number below)

In addition, testing with populating in a secondary thread yield great result
combining the best of each approach. This might be implemented in later
changesets.

In all cases, using mmap has a great effect on memory usage when many processes
run in parallel on the same machine.

### Benchmarks

# What did I run

A couple of month back I ran a large benchmark campaign to assess the impact of
various approach for using mmap with the revlog (and other files), it
highlighted a few benchmarks that capture the impact of the changes well. So to
validate this change I checked the following:

- log command displaying various revisions
  (read the changelog index)
- log command displaying the patch of listed revisions
  (read the changelog index, the manifest index and a few files indexes)
- unbundling a few revisions
  (read and write changelog, manifest and few files indexes, and walk the graph
  to update some cache)
- pushing a few revisions
  (read and write changelog, manifest and few files indexes, walk the graph to
  update some cache, performs various accesses locally and remotely during
  discovery)

Benchmarks were run using the default module policy (c+py) and the rust one. No
significant difference were found between the two implementation, so we will
present result using the default policy (unless otherwise specified).

I ran them on a few repositories :

- mercurial: a "public changeset only" copy of mercurial from 2018-08-01 using
  zstd compression and sparse-revlog

- pypy: a copy of pypy from 2018-08-01 using zstd compression and sparse-revlog

- netbeans: a copy of netbeans from 2018-08-01 using zstd compression and
  sparse-revlog

- mozilla-try: a copy of mozilla-try from 2019-02-18 using zstd compression and
  sparse-revlog

- mozilla-try persistent-nodemap: Same as the above but with a persistent
  nodemap. Used for the log --patch benchmark only

# Results

For the smaller repositories (mercurial, pypy), the impact of mmap is almost
imperceptible, other cost dominating the operation. The impact of prepopulating
is undiscernible in the benchmark we ran.

For larger repositories the benchmark support explanation given above:

On netbeans, the log can be about 1% faster without repopulation (for a
difference < 100ms) but unbundle becomes a bit slower, even when small.

### data-env-vars.name                             = netbeans-2018-08-01-zstd-sparse-revlog
  # benchmark.name                                 = hg.command.unbundle
  # benchmark.variants.issue6528                   = disabled
  # benchmark.variants.reuse-external-delta-parent = yes
  # benchmark.variants.revs                        = any-1-extra-rev
  # benchmark.variants.source                      = unbundle
  # benchmark.variants.verbosity                   = quiet
with-populate: 0.240157
no-populate:   0.265087  (+10.38%, +0.02)
  # benchmark.variants.revs                        = any-100-extra-rev
with-populate: 1.459518
no-populate:   1.481290   (+1.49%, +0.02)
 ## benchmark.name                                 = hg.command.push
  # benchmark.variants.explicit-rev                = none
  # benchmark.variants.issue6528                   = disabled
  # benchmark.variants.protocol                    = ssh
  # benchmark.variants.reuse-external-delta-parent = yes
  # benchmark.variants.revs                        = any-1-extra-rev
with-populate: 0.771919
no-populate:   0.792025   (+2.60%, +0.02)
  # benchmark.variants.revs                        = any-100-extra-rev
with-populate: 1.459518
no-populate:   1.481290   (+1.49%, +0.02)


For mozilla-try, the "slow down" from pre-populate for small `hg log` is more
visible, but still small in absolute time. (using rust value for the persistent
nodemap value to be relevant).

### data-env-vars.name            = mozilla-try-2019-02-18-ds2-pnm
  # benchmark.name                = hg.command.log
  # bin-env-vars.hg.flavor        = rust
  # benchmark.variants.patch      = yes
  # benchmark.variants.limit-rev  = 1
with-populate: 0.237813
no-populate:   0.229452   (-3.52%, -0.01)
  # benchmark.variants.limit-rev  = 10
  # benchmark.variants.patch      = yes
with-populate: 1.213578
no-populate:   1.205189
### data-env-vars.name            = mozilla-try-2019-02-18-zstd-sparse-revlog
  # benchmark.variants.limit-rev  = 1000
  # benchmark.variants.patch      = no
  # benchmark.variants.rev        = tip
with-populate: 0.198607
no-populate:   0.195038   (-1.80%, -0.00)

However pre-populating provide a significant boost on more complex operations
like unbundle or push:

### data-env-vars.name                             = mozilla-try-2019-02-18-zstd-sparse-revlog
  # benchmark.name                                 = hg.command.push
  # benchmark.variants.explicit-rev                = none
  # benchmark.variants.issue6528                   = disabled
  # benchmark.variants.protocol                    = ssh
  # benchmark.variants.reuse-external-delta-parent = yes
  # benchmark.variants.revs                        = any-1-extra-rev
with-populate: 4.798632
no-populate:   4.953295   (+3.22%, +0.15)
  # benchmark.variants.revs                        = any-100-extra-rev
with-populate: 4.903618
no-populate:   5.014963   (+2.27%, +0.11)
 ## benchmark.name                                 = hg.command.unbundle
  # benchmark.variants.revs                        = any-1-extra-rev
with-populate: 1.423411
no-populate:   1.585365  (+11.38%, +0.16)
  # benchmark.variants.revs                        = any-100-extra-rev
with-populate: 1.537909
no-populate:   1.688489   (+9.79%, +0.15)

#testcases flat tree
  $ . "$TESTDIR/narrow-library.sh"

#if tree
  $ cat << EOF >> $HGRCPATH
  > [experimental]
  > treemanifest = 1
  > EOF
#endif

  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [narrow]
  > serveellipses=True
  > EOF

  $ mkdir inside
  $ echo 'inside' > inside/f
  $ hg add inside/f
  $ hg commit -m 'add inside'

  $ mkdir widest
  $ echo 'widest' > widest/f
  $ hg add widest/f
  $ hg commit -m 'add widest'

  $ mkdir outside
  $ echo 'outside' > outside/f
  $ hg add outside/f
  $ hg commit -m 'add outside'

  $ cd ..

narrow clone the inside file

  $ hg clone --narrow ssh://user@dummy/master narrow --include inside
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 1 changes to 1 files
  new changesets *:* (glob)
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd narrow
  $ hg tracked
  I path:inside
  $ ls -A
  .hg
  inside
  $ cat inside/f
  inside
  $ cd ..

add more upstream files which we will include in a wider narrow spec

  $ cd master

  $ mkdir wider
  $ echo 'wider' > wider/f
  $ hg add wider/f
  $ echo 'widest v2' > widest/f
  $ hg commit -m 'add wider, update widest'

  $ echo 'widest v3' > widest/f
  $ hg commit -m 'update widest v3'

  $ echo 'inside v2' > inside/f
  $ hg commit -m 'update inside'

  $ mkdir outside2
  $ echo 'outside2' > outside2/f
  $ hg add outside2/f
  $ hg commit -m 'add outside2'

  $ echo 'widest v4' > widest/f
  $ hg commit -m 'update widest v4'

  $ hg log -T "{if(ellipsis, '...')}{rev}: {desc}\n"
  7: update widest v4
  6: add outside2
  5: update inside
  4: update widest v3
  3: add wider, update widest
  2: add outside
  1: add widest
  0: add inside

  $ cd ..

Testing the --import-rules flag of `hg tracked` command

  $ cd narrow
  $ hg tracked --import-rules
  hg tracked: option --import-rules requires argument
  hg tracked [OPTIONS]... [REMOTE]
  
  show or change the current narrowspec
  
  options ([+] can be repeated):
  
      --addinclude VALUE [+]       new paths to include
      --removeinclude VALUE [+]    old paths to no longer include
      --auto-remove-includes       automatically choose unused includes to
                                   remove
      --addexclude VALUE [+]       new paths to exclude
      --import-rules VALUE         import narrowspecs from a file
      --removeexclude VALUE [+]    old paths to no longer exclude
      --clear                      whether to replace the existing narrowspec
      --force-delete-local-changes forces deletion of local changes when
                                   narrowing
      --[no-]backup                back up local changes when narrowing
                                   (default: on)
      --update-working-copy        update working copy when the store has
                                   changed
   -e --ssh CMD                    specify ssh command to use
      --remotecmd CMD              specify hg command to run on the remote side
      --insecure                   do not verify server certificate (ignoring
                                   web.cacerts config)
  
  (use 'hg tracked -h' to show more help)
  [10]
  $ hg tracked --import-rules doesnotexist
  abort: cannot read narrowspecs from '$TESTTMP/narrow/doesnotexist': $ENOENT$
  [50]

  $ cat > specs <<EOF
  > %include foo
  > [include]
  > path:widest/
  > [exclude]
  > path:inside/
  > EOF

  $ hg tracked --import-rules specs
  abort: including other spec files using '%include' is not supported in narrowspec
  [10]

  $ cat > specs <<EOF
  > [include]
  > outisde
  > [exclude]
  > inside
  > EOF

  $ hg tracked --import-rules specs
  comparing with ssh://user@dummy/master
  searching for changes
  looking for local changes to affected paths
  deleting data/inside/f.i
  deleting meta/inside/00manifest.i (tree !)
  deleting unwanted files from working copy
  saved backup bundle to $TESTTMP/narrow/.hg/strip-backup/*-widen.hg (glob)
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 0 changes to 0 files
  $ hg tracked
  I path:outisde
  X path:inside

Testing the --import-rules flag with --addinclude and --addexclude

  $ cat > specs <<EOF
  > [include]
  > widest
  > EOF

  $ hg tracked --import-rules specs --addinclude 'wider/'
  comparing with ssh://user@dummy/master
  searching for changes
  saved backup bundle to $TESTTMP/narrow/.hg/strip-backup/*-widen.hg (glob)
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 1 changes to 1 files
  $ hg tracked
  I path:outisde
  I path:wider
  I path:widest
  X path:inside

  $ cat > specs <<EOF
  > [exclude]
  > outside2
  > EOF

  $ hg tracked --import-rules specs --addexclude 'widest'
  comparing with ssh://user@dummy/master
  searching for changes
  looking for local changes to affected paths
  deleting data/widest/f.i
  deleting meta/widest/00manifest.i (tree !)
  deleting unwanted files from working copy
  $ hg tracked
  I path:outisde
  I path:wider
  X path:inside
  X path:outside2
  X path:widest

  $ hg tracked --import-rules specs --clear
  abort: the --clear option is not yet supported
  [10]

Testing with passing a out of wdir file

  $ cat > ../nspecs <<EOF
  > [include]
  > widest
  > EOF

  $ hg tracked --import-rules ../nspecs
  comparing with ssh://user@dummy/master
  searching for changes
  saved backup bundle to $TESTTMP/narrow/.hg/strip-backup/*-widen.hg (glob)
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 0 changes to 0 files

  $ cd ..

Testing tracked command on a non-narrow repo

  $ hg init non-narrow
  $ cd non-narrow
  $ hg tracked --addinclude foobar
  abort: the tracked command is only supported on repositories cloned with --narrow
  [10]