tests/test-remove.t

revlog: don't flush data file after every added revision

The current behavior of revlogs is to flush the data file when writing
data to it. Tracing system calls revealed that changegroup processing
incurred numerous write(2) calls for values much smaller than the
default buffer size (Python defaults to 4096, but it can be adjusted
based on detected block size at run time by CPython).

The reason we flush revlogs is so readers have all data available.
For example, the current code in revlog.py will re-open the revlog
file (instead of seeking an existing file handle) to read the text
of a revision. This happens when starting a new delta chain when
adding several revisions from changegroups, for example. Yes, this
is likely sub-optimal (we should probably be sharing file descriptors
between readers and writers to avoid the flushing and associated
overhead of re-opening files).

While flushing revlogs is necessary, it appears all callers are
diligent about flushing files before a read is performed (see
buildtext() in _addrevision()), making the flush in
_writeentry() redundant and unncessary. So, we remove it. In practice,
this means we incur a write(2) a) when the buffer is full (typically
4096 bytes) b) when a new delta chain is created rather than after
every added revision. This applies to every revlog, but by volume
it mostly impacts filelogs.

Removing the redundant flush from _writeentry() significantly
reduces the number of write(2) calls during changegroup processing on
my Linux machine. When applying a changegroup of the hg repo based on
my local repo, the total number of write(2) calls during application
of the mercurial/localrepo.py revlogs dropped from 1,320 to 217 with
this patch applied. Total I/O related system calls dropped from 1,577
to 474.

When unbundling a mozilla-central gzipped bundle (264,403 changesets
with 1,492,215 changes to 222,507 files), total write(2) calls
dropped from 1,252,881 to 827,106 and total system calls dropped from
3,601,259 to 3,178,636 - a reduction of 425,775!

While the system call reduction is significant, it appears
to have no impact on wall time on my Linux and Windows machines. Still,
fewer syscalls is fewer syscalls. Surely this can't hurt. If nothing
else, it makes examining remaining system call usage simpler and opens
the door to experimenting with the performance impact of different
buffer sizes.

  $ remove() {
  >     hg rm $@
  >     echo "exit code: $?"
  >     hg st
  >     # do not use ls -R, which recurses in .hg subdirs on Mac OS X 10.5
  >     find . -name .hg -prune -o -type f -print | sort
  >     hg up -C
  > }

  $ hg init a
  $ cd a
  $ echo a > foo

file not managed

  $ remove foo
  not removing foo: file is untracked
  exit code: 1
  ? foo
  ./foo
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg add foo
  $ hg commit -m1

the table cases
00 state added, options none

  $ echo b > bar
  $ hg add bar
  $ remove bar
  not removing bar: file has been marked for add (use forget to undo)
  exit code: 1
  A bar
  ./bar
  ./foo
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved

01 state clean, options none

  $ remove foo
  exit code: 0
  R foo
  ? bar
  ./bar
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

02 state modified, options none

  $ echo b >> foo
  $ remove foo
  not removing foo: file is modified (use -f to force removal)
  exit code: 1
  M foo
  ? bar
  ./bar
  ./foo
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

03 state missing, options none

  $ rm foo
  $ remove foo
  exit code: 0
  R foo
  ? bar
  ./bar
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

10 state added, options -f

  $ echo b > bar
  $ hg add bar
  $ remove -f bar
  exit code: 0
  ? bar
  ./bar
  ./foo
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm bar

11 state clean, options -f

  $ remove -f foo
  exit code: 0
  R foo
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

12 state modified, options -f

  $ echo b >> foo
  $ remove -f foo
  exit code: 0
  R foo
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

13 state missing, options -f

  $ rm foo
  $ remove -f foo
  exit code: 0
  R foo
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

20 state added, options -A

  $ echo b > bar
  $ hg add bar
  $ remove -A bar
  not removing bar: file still exists
  exit code: 1
  A bar
  ./bar
  ./foo
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved

21 state clean, options -A

  $ remove -A foo
  not removing foo: file still exists
  exit code: 1
  ? bar
  ./bar
  ./foo
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved

22 state modified, options -A

  $ echo b >> foo
  $ remove -A foo
  not removing foo: file still exists
  exit code: 1
  M foo
  ? bar
  ./bar
  ./foo
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

23 state missing, options -A

  $ rm foo
  $ remove -A foo
  exit code: 0
  R foo
  ? bar
  ./bar
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

30 state added, options -Af

  $ echo b > bar
  $ hg add bar
  $ remove -Af bar
  exit code: 0
  ? bar
  ./bar
  ./foo
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ rm bar

31 state clean, options -Af

  $ remove -Af foo
  exit code: 0
  R foo
  ./foo
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

32 state modified, options -Af

  $ echo b >> foo
  $ remove -Af foo
  exit code: 0
  R foo
  ./foo
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

33 state missing, options -Af

  $ rm foo
  $ remove -Af foo
  exit code: 0
  R foo
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

test some directory stuff

  $ mkdir test
  $ echo a > test/foo
  $ echo b > test/bar
  $ hg ci -Am2
  adding test/bar
  adding test/foo

dir, options none

  $ rm test/bar
  $ remove test
  removing test/bar (glob)
  removing test/foo (glob)
  exit code: 0
  R test/bar
  R test/foo
  ./foo
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

dir, options -f

  $ rm test/bar
  $ remove -f test
  removing test/bar (glob)
  removing test/foo (glob)
  exit code: 0
  R test/bar
  R test/foo
  ./foo
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

dir, options -A

  $ rm test/bar
  $ remove -A test
  not removing test/foo: file still exists (glob)
  removing test/bar (glob)
  exit code: 1
  R test/bar
  ./foo
  ./test/foo
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

dir, options -Af

  $ rm test/bar
  $ remove -Af test
  removing test/bar (glob)
  removing test/foo (glob)
  exit code: 0
  R test/bar
  R test/foo
  ./foo
  ./test/foo
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

test remove dropping empty trees (issue1861)

  $ mkdir -p issue1861/b/c
  $ echo x > issue1861/x
  $ echo y > issue1861/b/c/y
  $ hg ci -Am add
  adding issue1861/b/c/y
  adding issue1861/x
  $ hg rm issue1861/b
  removing issue1861/b/c/y (glob)
  $ hg ci -m remove
  $ ls issue1861
  x

test that commit does not crash if the user removes a newly added file

  $ touch f1
  $ hg add f1
  $ rm f1
  $ hg ci -A -mx
  removing f1
  nothing changed
  [1]

handling of untracked directories and missing files

  $ mkdir d1
  $ echo a > d1/a
  $ hg rm --after d1
  not removing d1: no tracked files
  [1]
  $ hg add d1/a
  $ rm d1/a
  $ hg rm --after d1
  removing d1/a (glob)
#if windows
  $ hg rm --after nosuch
  nosuch: * (glob)
  [1]
#else
  $ hg rm --after nosuch
  nosuch: No such file or directory
  [1]
#endif