view tests/test-pathconflicts-update.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

Path conflict checking is currently disabled by default because of issue5716.
Turn it on for this test.

  $ cat >> $HGRCPATH << EOF
  > [experimental]
  > merge.checkpathconflicts=True
  > EOF

  $ hg init repo
  $ cd repo
  $ echo base > base
  $ hg add base
  $ hg commit -m "base"
  $ hg bookmark -i base
  $ mkdir a
  $ echo 1 > a/b
  $ hg add a/b
  $ hg commit -m "file"
  $ hg bookmark -i file
  $ echo 2 > a/b
  $ hg commit -m "file2"
  $ hg bookmark -i file2
  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mkdir a
#if symlink
  $ ln -s c a/b
#else
  $ touch a/b
#endif
  $ hg add a/b
  $ hg commit -m "link"
  created new head
  $ hg bookmark -i link
  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mkdir -p a/b/c
  $ echo 2 > a/b/c/d
  $ hg add a/b/c/d
  $ hg commit -m "dir"
  created new head
  $ hg bookmark -i dir

Update - local file conflicts with remote directory:

  $ hg up -q 0
  $ mkdir a
  $ echo 9 > a/b
  $ hg up dir
  a/b: untracked file conflicts with directory
  abort: untracked files in working directory differ from files in requested revision
  [255]
  $ hg up dir --config merge.checkunknown=warn
  a/b: replacing untracked file
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (activating bookmark dir)
  $ cat a/b.orig
  9
  $ rm a/b.orig

Update - local symlink conflicts with remote directory:

  $ hg up -q 0
  $ mkdir a
#if symlink
  $ ln -s x a/b
#else
  $ touch a/b
#endif
  $ hg up dir
  a/b: untracked file conflicts with directory
  abort: untracked files in working directory differ from files in requested revision
  [255]
  $ hg up dir --config merge.checkunknown=warn
  a/b: replacing untracked file
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (activating bookmark dir)
#if symlink
  $ readlink.py a/b.orig
  a/b.orig -> x
#endif
  $ rm a/b.orig

Update - local directory conflicts with remote file

  $ hg up -q 0
  $ mkdir -p a/b/c
  $ echo 9 > a/b/c/d
  $ hg up file
  a/b: untracked directory conflicts with file
  abort: untracked files in working directory differ from files in requested revision
  [255]
  $ hg up file --config merge.checkunknown=warn
  a/b: replacing untracked files in directory
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (activating bookmark file)
  $ cat a/b
  1
  $ test -d a/b.orig
  $ rm -rf a/b.orig

Update - local directory conflicts with remote symlink

  $ hg up -q 0
  $ mkdir -p a/b/c
  $ echo 9 > a/b/c/d
  $ hg up link
  a/b: untracked directory conflicts with file
  abort: untracked files in working directory differ from files in requested revision
  [255]
  $ hg up link --config merge.checkunknown=warn
  a/b: replacing untracked files in directory
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (activating bookmark link)
#if symlink
  $ readlink.py a/b
  a/b -> c
#endif
  $ test -d a/b.orig
  $ rm -rf a/b.orig

Update - local renamed file conflicts with remote directory

  $ hg up -q 0
  $ hg mv base a
  $ hg status -C
  A a
    base
  R base
  $ hg up --check dir
  abort: uncommitted changes
  [255]
  $ hg up dir
  a: path conflict - a file or link has the same name as a directory
  the local file has been renamed to a~d20a80d4def3
  resolve manually then use 'hg resolve --mark a'
  1 files updated, 0 files merged, 0 files removed, 1 files unresolved
  use 'hg resolve' to retry unresolved file merges
  (activating bookmark dir)
  [1]
  $ hg status -C
  A a~d20a80d4def3
    base
  R base
  $ hg resolve --list
  P a
  $ hg up --clean -q 0

Update clean - local directory conflicts with changed remote file

  $ hg up -q file
  $ rm a/b
  $ mkdir a/b
  $ echo 9 > a/b/c
  $ hg up file2 --check --config merge.checkunknown=warn
  abort: uncommitted changes
  [255]
  $ hg up file2 --clean
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (activating bookmark file2)