view tests/test-mq-qclone-http.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

hide outer repo
  $ hg init

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "mq=" >> $HGRCPATH
  $ mkdir webdir
  $ cd webdir
  $ hg init a
  $ hg --cwd a qinit -c
  $ echo a > a/a
  $ hg --cwd a ci -A -m a
  adding a
  $ echo b > a/b
  $ hg --cwd a addremove
  adding b
  $ hg --cwd a qnew -f b.patch
  $ hg --cwd a qcommit -m b.patch
  $ hg --cwd a log --template "{desc}\n"
  [mq]: b.patch
  a
  $ hg --cwd a/.hg/patches log --template "{desc}\n"
  b.patch
  $ root=`pwd`
  $ cd ..

test with recursive collection

  $ cat > collections.conf <<EOF
  > [paths]
  > /=$root/**
  > EOF
  $ hg serve -p $HGPORT -d --pid-file=hg.pid --webdir-conf collections.conf \
  >     -A access-paths.log -E error-paths-1.log
  $ cat hg.pid >> $DAEMON_PIDS
  $ get-with-headers.py localhost:$HGPORT '?style=raw'
  200 Script output follows
  
  
  /a/
  /a/.hg/patches/
  
  $ hg qclone http://localhost:$HGPORT/a b
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 2 files
  new changesets cb9a9f314b8b:184916345baa
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 3 changes to 3 files
  new changesets 4052ceaa8c4e
  updating to branch default
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg --cwd b log --template "{desc}\n"
  a
  $ hg --cwd b qpush -a
  applying b.patch
  now at: b.patch
  $ hg --cwd b log --template "{desc}\n"
  imported patch b.patch
  a

test with normal collection

  $ cat > collections1.conf <<EOF
  > [paths]
  > /=$root/*
  > EOF
  $ hg serve -p $HGPORT1 -d --pid-file=hg.pid --webdir-conf collections1.conf \
  >     -A access-paths.log -E error-paths-1.log
  $ cat hg.pid >> $DAEMON_PIDS
  $ get-with-headers.py localhost:$HGPORT1 '?style=raw'
  200 Script output follows
  
  
  /a/
  /a/.hg/patches/
  
  $ hg qclone http://localhost:$HGPORT1/a c
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 2 files
  new changesets cb9a9f314b8b:184916345baa
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 3 changes to 3 files
  new changesets 4052ceaa8c4e
  updating to branch default
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg --cwd c log --template "{desc}\n"
  a
  $ hg --cwd c qpush -a
  applying b.patch
  now at: b.patch
  $ hg --cwd c log --template "{desc}\n"
  imported patch b.patch
  a

test with old-style collection

  $ cat > collections2.conf <<EOF
  > [collections]
  > $root=$root
  > EOF
  $ hg serve -p $HGPORT2 -d --pid-file=hg.pid --webdir-conf collections2.conf \
  >     -A access-paths.log -E error-paths-1.log
  $ cat hg.pid >> $DAEMON_PIDS
  $ get-with-headers.py localhost:$HGPORT2 '?style=raw'
  200 Script output follows
  
  
  /a/
  /a/.hg/patches/
  
  $ hg qclone http://localhost:$HGPORT2/a d
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 2 files
  new changesets cb9a9f314b8b:184916345baa
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 3 changes to 3 files
  new changesets 4052ceaa8c4e
  updating to branch default
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg --cwd d log --template "{desc}\n"
  a
  $ hg --cwd d qpush -a
  applying b.patch
  now at: b.patch
  $ hg --cwd d log --template "{desc}\n"
  imported patch b.patch
  a

test --mq works and uses correct repository config

  $ hg --cwd d outgoing --mq
  comparing with http://localhost:$HGPORT2/a/.hg/patches
  searching for changes
  no changes found
  [1]
  $ hg --cwd d log --mq --template '{rev} {desc|firstline}\n'
  0 b.patch

  $ killdaemons.py