view tests/test-issue1802.t @ 30289:1f92056c4066

revlog: optimize _chunkraw when startrev==endrev

In many cases, _chunkraw() is called with startrev==endrev. When
this is true, we can avoid an extra index lookup and some other
minor operations.

On the mozilla-unified repo, `hg perfrevlogchunks -c` says this
has the following impact:

! read w/ reused fd
! wall 0.371846 comb 0.370000 user 0.350000 sys 0.020000 (best of 27)
! wall 0.337930 comb 0.330000 user 0.300000 sys 0.030000 (best of 30)

! read batch w/ reused fd
! wall 0.014952 comb 0.020000 user 0.000000 sys 0.020000 (best of 197)
! wall 0.014866 comb 0.010000 user 0.000000 sys 0.010000 (best of 196)

So, we've gone from ~25x slower than batch to ~22.5x slower.

At this point, there's probably not much else we can do except
implement an optimized function in the index itself, including in C.

#require execbit

Create extension that can disable exec checks:

  $ cat > noexec.py <<EOF
  > from mercurial import extensions, util
  > def setflags(orig, f, l, x):
  >     pass
  > def checkexec(orig, path):
  >     return False
  > def extsetup(ui):
  >     extensions.wrapfunction(util, 'setflags', setflags)
  >     extensions.wrapfunction(util, 'checkexec', checkexec)
  > EOF

  $ hg init unix-repo
  $ cd unix-repo
  $ touch a
  $ hg add a
  $ hg commit -m 'unix: add a'
  $ hg clone . ../win-repo
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ chmod +x a
  $ hg commit -m 'unix: chmod a'
  $ hg manifest -v
  755 * a

  $ cd ../win-repo

  $ touch b
  $ hg add b
  $ hg commit -m 'win: add b'

  $ hg manifest -v
  644   a
  644   b

  $ hg pull
  pulling from $TESTTMP/unix-repo
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files (+1 heads)
  (run 'hg heads' to see heads, 'hg merge' to merge)

  $ hg manifest -v -r tip
  755 * a

Simulate a Windows merge:

  $ hg --config extensions.n=$TESTTMP/noexec.py merge --debug
    searching for copies back to rev 1
    unmatched files in local:
     b
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: a03b0deabf2b, local: d6fa54f68ae1+, remote: 2d8bcf2dda39
   a: update permissions -> e
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

Simulate a Windows commit:

  $ hg --config extensions.n=$TESTTMP/noexec.py commit -m 'win: merge'

  $ hg manifest -v
  755 * a
  644   b

  $ cd ..