view tests/test-unamend.t @ 38732:be4984261611

merge: mark file gets as not thread safe (issue5933)

In default installs, this has the effect of disabling the thread-based
worker on Windows when manifesting files in the working directory. My
measurements have shown that with revlog-based repositories, Mercurial
spends a lot of CPU time in revlog code resolving file data. This ends
up incurring a lot of context switching across threads and slows down
`hg update` operations when going from an empty working directory to
the tip of the repo.

On mozilla-unified (246,351 files) on an i7-6700K (4+4 CPUs):

before: 487s wall
after:  360s wall (equivalent to worker.enabled=false)
cpus=2: 379s wall

Even with only 2 threads, the thread pool is still slower.

The introduction of the thread-based worker (02b36e860e0b) states that
it resulted in a "~50%" speedup for `hg sparse --enable-profile` and
`hg sparse --disable-profile`. This disagrees with my measurement
above. I theorize a few reasons for this:

1) Removal of files from the working directory is I/O - not CPU - bound
   and should benefit from a thread pool (unless I/O is insanely fast
   and the GIL release is near instantaneous). So tests like `hg sparse
   --enable-profile` may exercise deletion throughput and aren't good
   benchmarks for worker tasks that are CPU heavy.
2) The patch was authored by someone at Facebook. The results were
   likely measured against a repository using remotefilelog. And I
   believe that revision retrieval during working directory updates with
   remotefilelog will often use a remote store, thus being I/O and not
   CPU bound. This probably resulted in an overstated performance gain.

Since there appears to be a need to enable the thread-based worker with
some stores, I've made the flagging of file gets as thread safe
configurable. I've made it experimental because I don't want to formalize
a boolean flag for this option and because this attribute is best
captured against the store implementation. But we don't have a proper
store API for this yet. I'd rather cross this bridge later.

It is possible there are revlog-based repositories that do benefit from
a thread-based worker. I didn't do very comprehensive testing. If there
are, we may want to devise a more proper algorithm for whether to use
the thread-based worker, including possibly config options to limit the
number of threads to use. But until I see evidence that justifies
complexity, simplicity wins.

Differential Revision: https://phab.mercurial-scm.org/D3963

Test for command `hg unamend` which lives in uncommit extension
===============================================================

  $ cat >> $HGRCPATH << EOF
  > [alias]
  > glog = log -G -T '{rev}:{node|short}  {desc}'
  > [experimental]
  > evolution = createmarkers, allowunstable
  > [extensions]
  > rebase =
  > amend =
  > uncommit =
  > EOF

Repo Setup

  $ hg init repo
  $ cd repo
  $ for ch in a b c d e f g h; do touch $ch; echo "foo" >> $ch; hg ci -Aqm "Added "$ch; done

  $ hg glog
  @  7:ec2426147f0e  Added h
  |
  o  6:87d6d6676308  Added g
  |
  o  5:825660c69f0c  Added f
  |
  o  4:aa98ab95a928  Added e
  |
  o  3:62615734edd5  Added d
  |
  o  2:28ad74487de9  Added c
  |
  o  1:29becc82797a  Added b
  |
  o  0:18d04c59bb5d  Added a
  
Trying to unamend when there was no amend done

  $ hg unamend
  abort: changeset must have one predecessor, found 0 predecessors
  [255]

Unamend on clean wdir and tip

  $ echo "bar" >> h
  $ hg amend

  $ hg exp
  # HG changeset patch
  # User test
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID c9fa1a715c1b7661c0fafb362a9f30bd75878d7d
  # Parent  87d6d66763085b629e6d7ed56778c79827273022
  Added h
  
  diff -r 87d6d6676308 -r c9fa1a715c1b h
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/h	Thu Jan 01 00:00:00 1970 +0000
  @@ -0,0 +1,2 @@
  +foo
  +bar

  $ hg glog --hidden
  @  8:c9fa1a715c1b  Added h
  |
  | x  7:ec2426147f0e  Added h
  |/
  o  6:87d6d6676308  Added g
  |
  o  5:825660c69f0c  Added f
  |
  o  4:aa98ab95a928  Added e
  |
  o  3:62615734edd5  Added d
  |
  o  2:28ad74487de9  Added c
  |
  o  1:29becc82797a  Added b
  |
  o  0:18d04c59bb5d  Added a
  
  $ hg unamend
  $ hg glog --hidden
  @  9:46d02d47eec6  Added h
  |
  | x  8:c9fa1a715c1b  Added h
  |/
  | x  7:ec2426147f0e  Added h
  |/
  o  6:87d6d6676308  Added g
  |
  o  5:825660c69f0c  Added f
  |
  o  4:aa98ab95a928  Added e
  |
  o  3:62615734edd5  Added d
  |
  o  2:28ad74487de9  Added c
  |
  o  1:29becc82797a  Added b
  |
  o  0:18d04c59bb5d  Added a
  
  $ hg diff
  diff -r 46d02d47eec6 h
  --- a/h	Thu Jan 01 00:00:00 1970 +0000
  +++ b/h	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,2 @@
   foo
  +bar

  $ hg exp
  # HG changeset patch
  # User test
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID 46d02d47eec6ca096b8dcab3f8f5579c40c3dd9a
  # Parent  87d6d66763085b629e6d7ed56778c79827273022
  Added h
  
  diff -r 87d6d6676308 -r 46d02d47eec6 h
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/h	Thu Jan 01 00:00:00 1970 +0000
  @@ -0,0 +1,1 @@
  +foo

  $ hg status
  M h

  $ hg log -r . -T '{extras % "{extra}\n"}' --config alias.log=log
  branch=default
  unamend_source=c9fa1a715c1b7661c0fafb362a9f30bd75878d7d

Using unamend to undo an unamed (intentional)

  $ hg unamend
  $ hg exp
  # HG changeset patch
  # User test
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID 850ddfc1bc662997ec6094ada958f01f0cc8070a
  # Parent  87d6d66763085b629e6d7ed56778c79827273022
  Added h
  
  diff -r 87d6d6676308 -r 850ddfc1bc66 h
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/h	Thu Jan 01 00:00:00 1970 +0000
  @@ -0,0 +1,2 @@
  +foo
  +bar
  $ hg diff

Unamend on a dirty working directory

  $ echo "bar" >> a
  $ hg amend
  $ echo "foobar" >> a
  $ echo "bar" >> b
  $ hg status
  M a
  M b

  $ hg unamend

  $ hg status
  M a
  M b

  $ hg diff
  diff -r ec338db45d51 a
  --- a/a	Thu Jan 01 00:00:00 1970 +0000
  +++ b/a	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,3 @@
   foo
  +bar
  +foobar
  diff -r ec338db45d51 b
  --- a/b	Thu Jan 01 00:00:00 1970 +0000
  +++ b/b	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,2 @@
   foo
  +bar

Unamending an added file

  $ hg ci -m "Added things to a and b"
  $ echo foo > bar
  $ hg add bar
  $ hg amend

  $ hg unamend
  $ hg status
  A bar

  $ hg revert --all
  forgetting bar

Unamending a removed file

  $ hg remove a
  $ hg amend

  $ hg unamend
  $ hg status
  R a
  ? bar

  $ hg revert --all
  undeleting a

Unamending an added file with dirty wdir status

  $ hg add bar
  $ hg amend
  $ echo bar >> bar
  $ hg status
  M bar

  $ hg unamend
  $ hg status
  A bar
  $ hg diff
  diff -r 7f79409af972 bar
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/bar	Thu Jan 01 00:00:00 1970 +0000
  @@ -0,0 +1,2 @@
  +foo
  +bar

  $ hg revert --all
  forgetting bar

Unamending in middle of a stack

  $ hg glog
  @  19:7f79409af972  Added things to a and b
  |
  o  12:ec338db45d51  Added h
  |
  o  6:87d6d6676308  Added g
  |
  o  5:825660c69f0c  Added f
  |
  o  4:aa98ab95a928  Added e
  |
  o  3:62615734edd5  Added d
  |
  o  2:28ad74487de9  Added c
  |
  o  1:29becc82797a  Added b
  |
  o  0:18d04c59bb5d  Added a
  
  $ hg up 5
  2 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ echo bar >> f
  $ hg amend
  3 new orphan changesets
  $ hg rebase -s 6 -d . -q

  $ hg glog
  o  23:03ddd6fc5af1  Added things to a and b
  |
  o  22:3e7b64ee157b  Added h
  |
  o  21:49635b68477e  Added g
  |
  @  20:93f0e8ffab32  Added f
  |
  o  4:aa98ab95a928  Added e
  |
  o  3:62615734edd5  Added d
  |
  o  2:28ad74487de9  Added c
  |
  o  1:29becc82797a  Added b
  |
  o  0:18d04c59bb5d  Added a
  

  $ hg --config experimental.evolution=createmarkers unamend
  abort: cannot unamend changeset with children
  [255]

  $ hg unamend
  3 new orphan changesets

Trying to unamend a public changeset

  $ hg up -C 23
  5 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg phase -r . -p
  1 new phase-divergent changesets
  $ hg unamend
  abort: cannot unamend public changesets
  (see 'hg help phases' for details)
  [255]

Testing whether unamend retains copies or not

  $ hg status
  ? bar

  $ hg mv a foo

  $ hg ci -m "Moved a to foo"
  $ hg exp --git
  # HG changeset patch
  # User test
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID cfef290346fbee5126313d7e1aab51d877679b09
  # Parent  03ddd6fc5af19e028c44a2fd6d790dd22712f231
  Moved a to foo
  
  diff --git a/a b/foo
  rename from a
  rename to foo

  $ hg mv b foobar
  $ hg diff --git
  diff --git a/b b/foobar
  rename from b
  rename to foobar
  $ hg amend

  $ hg exp --git
  # HG changeset patch
  # User test
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID eca050985275bb271ce3092b54e56ea5c85d29a3
  # Parent  03ddd6fc5af19e028c44a2fd6d790dd22712f231
  Moved a to foo
  
  diff --git a/a b/foo
  rename from a
  rename to foo
  diff --git a/b b/foobar
  rename from b
  rename to foobar

  $ hg mv c wat
  $ hg unamend

Retained copies in new prdecessor commit

  $ hg exp --git
  # HG changeset patch
  # User test
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID 552e3af4f01f620f88ca27be1f898316235b736a
  # Parent  03ddd6fc5af19e028c44a2fd6d790dd22712f231
  Moved a to foo
  
  diff --git a/a b/foo
  rename from a
  rename to foo

Retained copies in working directoy

  $ hg diff --git
  diff --git a/b b/foobar
  rename from b
  rename to foobar
  diff --git a/c b/wat
  rename from c
  rename to wat