view tests/test-narrow-exchange.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

  $ . "$TESTDIR/narrow-library.sh"

create full repo

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

  $ mkdir inside
  $ echo 1 > inside/f
  $ mkdir inside2
  $ echo 1 > inside2/f
  $ mkdir outside
  $ echo 1 > outside/f
  $ hg ci -Aqm 'initial'

  $ echo 2 > inside/f
  $ hg ci -qm 'inside 2'

  $ echo 2 > inside2/f
  $ hg ci -qm 'inside2 2'

  $ echo 2 > outside/f
  $ hg ci -qm 'outside 2'

  $ cd ..

  $ hg clone --narrow ssh://user@dummy/master narrow --include inside
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 2 changes to 1 files
  new changesets *:* (glob)
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg clone --narrow ssh://user@dummy/master narrow2 --include inside --include inside2
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 4 changesets with 4 changes to 2 files
  new changesets *:* (glob)
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

Can push to wider repo if change does not affect paths in wider repo that are
not also in narrower repo

  $ cd narrow
  $ echo 3 > inside/f
  $ hg ci -m 'inside 3'
  $ hg push ssh://user@dummy/narrow2
  pushing to ssh://user@dummy/narrow2
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 1 changesets with 1 changes to 1 files

Can push to narrower repo if change affects only paths within remote's
narrow spec

  $ cd ../narrow2
  $ cat >> .hg/hgrc <<EOF
  > [narrow]
  > serveellipses=True
  > EOF
  $ hg co -r 'desc("inside 3")'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo 4 > inside/f
  $ hg ci -m 'inside 4'
  $ hg push ssh://user@dummy/narrow
  pushing to ssh://user@dummy/narrow
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 1 changesets with 1 changes to 1 files

Can push to narrow repo if change affects only paths outside remote's
narrow spec

  $ echo 3 > inside2/f
  $ hg ci -m 'inside2 3'
TODO: this should be successful
  $ hg push ssh://user@dummy/narrow
  pushing to ssh://user@dummy/narrow
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: transaction abort!
  remote: rollback completed
  remote: abort: data/inside2/f.i@4a1aa07735e6: unknown parent! (reporevlogstore !)
  remote: abort: data/inside2/f/index@4a1aa07735e6: no node! (reposimplestore !)
  abort: stream ended unexpectedly (got 0 bytes, expected 4)
  [255]

Can pull from wider repo if change affects only paths outside remote's
narrow spec
  $ echo 4 > inside2/f
  $ hg ci -m 'inside2 4'
  $ hg log -G -T '{rev} {node|short} {files}\n'
  @  7 d78a96df731d inside2/f
  |
  o  6 8c26f5218962 inside2/f
  |
  o  5 ba3480e2f9de inside/f
  |
  o  4 4e5edd526618 inside/f
  |
  o  3 81e7e07b7ab0 outside/f
  |
  o  2 f3993b8c0c2b inside2/f
  |
  o  1 8cd66ca966b4 inside/f
  |
  o  0 c8057d6f53ab inside/f inside2/f outside/f
  
  $ cd ../narrow
  $ hg log -G -T '{rev} {node|short} {files}\n'
  o  4 ba3480e2f9de inside/f
  |
  @  3 4e5edd526618 inside/f
  |
  o  2 81e7e07b7ab0 outside/f
  |
  o  1 8cd66ca966b4 inside/f
  |
  o  0 c8057d6f53ab inside/f inside2/f outside/f
  
  $ hg pull ssh://user@dummy/narrow2
  pulling from ssh://user@dummy/narrow2
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files
  new changesets d78a96df731d
  (run 'hg update' to get a working copy)

Check that the resulting history is valid in the full repo

  $ cd ../narrow2
  $ hg push ssh://user@dummy/master
  pushing to ssh://user@dummy/master
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 4 changesets with 4 changes to 2 files
  $ cd ../master
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  3 files, 8 changesets, 10 total revisions

Can not push to wider repo if change affects paths in wider repo that are
not also in narrower repo
  $ cd ../master
  $ hg co -r 'desc("inside2 4")'
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo 5 > inside2/f
  $ hg ci -m 'inside2 5'
  $ hg log -G -T '{rev} {node|short} {files}\n'
  @  8 5970befb64ba inside2/f
  |
  o  7 d78a96df731d inside2/f
  |
  o  6 8c26f5218962 inside2/f
  |
  o  5 ba3480e2f9de inside/f
  |
  o  4 4e5edd526618 inside/f
  |
  o  3 81e7e07b7ab0 outside/f
  |
  o  2 f3993b8c0c2b inside2/f
  |
  o  1 8cd66ca966b4 inside/f
  |
  o  0 c8057d6f53ab inside/f inside2/f outside/f
  
  $ cd ../narrow
  $ hg pull
  pulling from ssh://user@dummy/master
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files
  new changesets * (glob)
  (run 'hg update' to get a working copy)
TODO: this should tell the user that their narrow clone does not have the
necessary content to be able to push to the target
  $ hg push ssh://user@dummy/narrow2
  pushing to ssh://user@dummy/narrow2
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 1 changesets with 0 changes to 0 files