view tests/test-rollback.t @ 30212:260af19891f2

changegroup: increase write buffer size to 128k

By default, Python defers to the operating system for choosing the
default buffer size on opened files. On my Linux machine, the default
is 4k, which is really small for 2016.

This patch bumps the write buffer size when writing
changegroups/bundles to 128k. This matches the 128k read buffer
we already use on revlogs.

It's worth noting that this only impacts when writing to an explicit
file (such as during `hg bundle`). Buffers when writing to bundle
files via the repo vfs or to a temporary file are not impacted.

When producing a none-v2 bundle file of the mozilla-unified repository,
this change caused the number of write() system calls to drop from
952,449 to 29,788. After this change, the most frequent system
calls are fstat(), read(), lseek(), and open(). There were
2,523,672 system calls after this patch (so a net decrease of
~950k is statistically significant).

This change shows no performance change on my system. But I have a
high-end system with a fast SSD. It is quite possible this change
will have a significant impact on network file systems, where
extra network round trips due to excessive I/O system calls could
introduce significant latency.

setup repo
  $ hg init t
  $ cd t
  $ echo a > a
  $ hg commit -Am'add a'
  adding a
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 1 changesets, 1 total revisions
  $ hg parents
  changeset:   0:1f0dee641bb7
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add a
  

rollback to null revision
  $ hg status
  $ hg rollback
  repository tip rolled back to revision -1 (undo commit)
  working directory now based on revision -1
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  0 files, 0 changesets, 0 total revisions
  $ hg parents
  $ hg status
  A a

Two changesets this time so we rollback to a real changeset
  $ hg commit -m'add a again'
  $ echo a >> a
  $ hg commit -m'modify a'

Test issue 902 (current branch is preserved)
  $ hg branch test
  marked working directory as branch test
  (branches are permanent and global, did you want a bookmark?)
  $ hg rollback
  repository tip rolled back to revision 0 (undo commit)
  working directory now based on revision 0
  $ hg branch
  default

Test issue 1635 (commit message saved)
  $ cat .hg/last-message.txt ; echo
  modify a

Test rollback of hg before issue 902 was fixed

  $ hg commit -m "test3"
  $ hg branch test
  marked working directory as branch test
  (branches are permanent and global, did you want a bookmark?)
  $ rm .hg/undo.branch
  $ hg rollback
  repository tip rolled back to revision 0 (undo commit)
  named branch could not be reset: current branch is still 'test'
  working directory now based on revision 0
  $ hg branch
  test

working dir unaffected by rollback: do not restore dirstate et. al.
  $ hg log --template '{rev}  {branch}  {desc|firstline}\n'
  0  default  add a again
  $ hg status
  M a
  $ hg bookmark foo
  $ hg commit -m'modify a again'
  $ echo b > b
  $ hg bookmark bar -r default #making bar active, before the transaction
  $ hg commit -Am'add b'
  adding b
  $ hg log --template '{rev}  {branch}  {desc|firstline}\n'
  2  test  add b
  1  test  modify a again
  0  default  add a again
  $ hg update bar
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (activating bookmark bar)
  $ cat .hg/undo.branch ; echo
  test
  $ hg rollback -f
  repository tip rolled back to revision 1 (undo commit)
  $ hg id -n
  0
  $ hg branch
  default
  $ cat .hg/bookmarks.current ; echo
  bar
  $ hg bookmark --delete foo bar

rollback by pretxncommit saves commit message (issue1635)

  $ echo a >> a
  $ hg --config hooks.pretxncommit=false commit -m"precious commit message"
  transaction abort!
  rollback completed
  abort: pretxncommit hook exited with status * (glob)
  [255]
  $ cat .hg/last-message.txt ; echo
  precious commit message

same thing, but run $EDITOR

  $ cat > editor.sh << '__EOF__'
  > echo "another precious commit message" > "$1"
  > __EOF__
  $ HGEDITOR="\"sh\" \"`pwd`/editor.sh\"" hg --config hooks.pretxncommit=false commit 2>&1
  note: commit message saved in .hg/last-message.txt
  transaction abort!
  rollback completed
  abort: pretxncommit hook exited with status * (glob)
  [255]
  $ cat .hg/last-message.txt
  another precious commit message

test rollback on served repository

#if serve
  $ hg commit -m "precious commit message"
  $ hg serve -p $HGPORT -d --pid-file=hg.pid -A access.log -E errors.log
  $ cat hg.pid >> $DAEMON_PIDS
  $ cd ..
  $ hg clone http://localhost:$HGPORT u
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 2 changes to 1 files (+1 heads)
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd u
  $ hg id default
  068774709090

now rollback and observe that 'hg serve' reloads the repository and
presents the correct tip changeset:

  $ hg -R ../t rollback
  repository tip rolled back to revision 1 (undo commit)
  working directory now based on revision 0
  $ hg id default
  791dd2169706
#endif

update to older changeset and then refuse rollback, because
that would lose data (issue2998)
  $ cd ../t
  $ hg -q update
  $ rm `hg status -un`
  $ template='{rev}:{node|short}  [{branch}]  {desc|firstline}\n'
  $ echo 'valuable new file' > b
  $ echo 'valuable modification' >> a
  $ hg commit -A -m'a valuable change'
  adding b
  $ hg update 0
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg rollback
  abort: rollback of last commit while not checked out may lose data
  (use -f to force)
  [255]
  $ hg tip -q
  2:4d9cd3795eea
  $ hg rollback -f
  repository tip rolled back to revision 1 (undo commit)
  $ hg status
  $ hg log --removed b   # yep, it's gone

same again, but emulate an old client that doesn't write undo.desc
  $ hg -q update
  $ echo 'valuable modification redux' >> a
  $ hg commit -m'a valuable change redux'
  $ rm .hg/undo.desc
  $ hg update 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg rollback
  rolling back unknown transaction
  $ cat a
  a

corrupt journal test
  $ echo "foo" > .hg/store/journal
  $ hg recover
  rolling back interrupted transaction
  couldn't read journal entry 'foo\n'!
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 2 changesets, 2 total revisions

rollback disabled by config
  $ cat >> $HGRCPATH <<EOF
  > [ui]
  > rollback = false
  > EOF
  $ echo narf >> pinky-sayings.txt
  $ hg add pinky-sayings.txt
  $ hg ci -m 'First one.'
  $ hg rollback
  abort: rollback is disabled because it is unsafe
  (see `hg help -v rollback` for information)
  [255]