view tests/test-notify-changegroup.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)

  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > notify=
  > 
  > [hooks]
  > changegroup.notify = python:hgext.notify.hook
  > 
  > [notify]
  > sources = push
  > diffstat = False
  > maxsubject = 10
  > 
  > [usersubs]
  > foo@bar = *
  > 
  > [reposubs]
  > * = baz
  > EOF
  $ hg init a

clone

  $ hg --traceback clone a b
  updating to branch default
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo a > b/a

commit

  $ hg --traceback --cwd b commit -Ama
  adding a
  $ echo a >> b/a

commit

  $ hg --traceback --cwd b commit -Amb

push

  $ hg --traceback --cwd b push ../a 2>&1 |
  >     "$PYTHON" $TESTDIR/unwrap-message-id.py | \
  >     "$PYTHON" -c 'import sys,re; print(re.sub("\n\t", " ", sys.stdin.read()), end="")'
  pushing to ../a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 1 files
  MIME-Version: 1.0
  Content-Type: text/plain; charset="us-ascii"
  Content-Transfer-Encoding: 7bit
  Date: * (glob)
  Subject: * (glob)
  From: test
  X-Hg-Notification: changeset cb9a9f314b8b
  Message-Id: <*> (glob)
  To: baz, foo@bar
  
  changeset cb9a9f314b8b in $TESTTMP/a
  details: $TESTTMP/a?cmd=changeset;node=cb9a9f314b8b
  summary: a
  
  changeset ba677d0156c1 in $TESTTMP/a
  details: $TESTTMP/a?cmd=changeset;node=ba677d0156c1
  summary: b
  
  diffs (6 lines):
  
  diff -r 000000000000 -r ba677d0156c1 a
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/a	Thu Jan 01 00:00:00 1970 +0000
  @@ -0,0 +1,2 @@
  +a
  +a
  $ hg --cwd a rollback
  repository tip rolled back to revision -1 (undo push)

unbundle with unrelated source

  $ hg --cwd b bundle ../test.hg ../a
  searching for changes
  2 changesets found
  $ hg --cwd a unbundle ../test.hg
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 1 files
  new changesets cb9a9f314b8b:ba677d0156c1 (2 drafts)
  (run 'hg update' to get a working copy)
  $ hg --cwd a rollback
  repository tip rolled back to revision -1 (undo unbundle)

unbundle with correct source

  $ hg --config notify.sources=unbundle --cwd a unbundle ../test.hg 2>&1 |
  >     "$PYTHON" $TESTDIR/unwrap-message-id.py | \
  >     "$PYTHON" -c 'import sys,re; print(re.sub("\n\t", " ", sys.stdin.read()), end="")'
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 1 files
  new changesets cb9a9f314b8b:ba677d0156c1 (2 drafts)
  MIME-Version: 1.0
  Content-Type: text/plain; charset="us-ascii"
  Content-Transfer-Encoding: 7bit
  Date: * (glob)
  Subject: * (glob)
  From: test
  X-Hg-Notification: changeset cb9a9f314b8b
  Message-Id: <*> (glob)
  To: baz, foo@bar
  
  changeset cb9a9f314b8b in $TESTTMP/a
  details: $TESTTMP/a?cmd=changeset;node=cb9a9f314b8b
  summary: a
  
  changeset ba677d0156c1 in $TESTTMP/a
  details: $TESTTMP/a?cmd=changeset;node=ba677d0156c1
  summary: b
  
  diffs (6 lines):
  
  diff -r 000000000000 -r ba677d0156c1 a
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/a	Thu Jan 01 00:00:00 1970 +0000
  @@ -0,0 +1,2 @@
  +a
  +a
  (run 'hg update' to get a working copy)

Check that using the first committer as the author of a changeset works:
Check that the config option works.
Check that the first committer is indeed used for "From:".
Check that the merge user is NOT used for "From:"

Create new file

  $ echo a > b/b
  $ echo b >> b/b
  $ echo c >> b/b
  $ hg --traceback --cwd b commit -Amnewfile -u committer_1
  adding b

commit as one user

  $ echo x > b/b
  $ echo b >> b/b
  $ echo c >> b/b
  $ hg --traceback --cwd b commit -Amx -u committer_2

commit as other user, change file so we can do an (automatic) merge

  $ hg --cwd b up 2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo a > b/b
  $ echo b >> b/b
  $ echo y >> b/b
  $ hg --traceback --cwd b commit -Amy -u committer_3
  created new head

merge as a different user

  $ hg --cwd b merge --config notify.fromauthor=True
  merging b
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg --traceback --cwd b commit -Am "merged"

push

  $ hg --traceback --cwd b --config notify.fromauthor=True push ../a 2>&1 |
  >     "$PYTHON" $TESTDIR/unwrap-message-id.py | \
  >     "$PYTHON" -c 'import sys,re; print(re.sub("\n\t", " ", sys.stdin.read()), end="")'
  pushing to ../a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 4 changesets with 4 changes to 1 files
  MIME-Version: 1.0
  Content-Type: text/plain; charset="us-ascii"
  Content-Transfer-Encoding: 7bit
  Date: * (glob)
  Subject: * (glob)
  From: committer_1
  X-Hg-Notification: changeset 84e487dddc58
  Message-Id: <*> (glob)
  To: baz, foo@bar
  
  changeset 84e487dddc58 in $TESTTMP/a
  details: $TESTTMP/a?cmd=changeset;node=84e487dddc58
  summary: newfile
  
  changeset b29c7a2b6b0c in $TESTTMP/a
  details: $TESTTMP/a?cmd=changeset;node=b29c7a2b6b0c
  summary: x
  
  changeset 0957c7d64886 in $TESTTMP/a
  details: $TESTTMP/a?cmd=changeset;node=0957c7d64886
  summary: y
  
  changeset 485b4e6b0249 in $TESTTMP/a
  details: $TESTTMP/a?cmd=changeset;node=485b4e6b0249
  summary: merged
  
  diffs (7 lines):
  
  diff -r ba677d0156c1 -r 485b4e6b0249 b
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/b	Thu Jan 01 00:00:00 1970 +0000
  @@ -0,0 +1,3 @@
  +x
  +b
  +y
  $ hg --cwd a rollback
  repository tip rolled back to revision 1 (undo push)