tests/test-mq-qimport.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.

#require killdaemons

  $ cat > writelines.py <<EOF
  > import sys
  > path = sys.argv[1]
  > args = sys.argv[2:]
  > assert (len(args) % 2) == 0
  > 
  > f = file(path, 'wb')
  > for i in xrange(len(args)/2):
  >    count, s = args[2*i:2*i+2]
  >    count = int(count)
  >    s = s.decode('string_escape')
  >    f.write(s*count)
  > f.close()
  > 
  > EOF
  > cat <<EOF >> $HGRCPATH
  > [extensions]
  > mq =
  > [diff]
  > git = 1
  > EOF
  $ hg init repo
  $ cd repo

qimport without file or revision

  $ hg qimport
  abort: no files or revisions specified
  [255]

qimport non-existing-file

  $ hg qimport non-existing-file
  abort: unable to read file non-existing-file
  [255]

qimport null revision

  $ hg qimport -r null
  abort: revision -1 is not mutable
  (see "hg help phases" for details)
  [255]
  $ hg qseries

import email

  $ hg qimport --push -n email - <<EOF
  > From: Username in email <[e-mail]>
  > Subject: [PATCH] Message in email
  > Date: Fri, 02 Jan 1970 00:00:00 +0000
  > 
  > Text before patch.
  > 
  > # HG changeset patch
  > # User Username in patch <[e-mail]>
  > # Date 0 0
  > # Node ID 1a706973a7d84cb549823634a821d9bdf21c6220
  > # Parent  0000000000000000000000000000000000000000
  > First line of commit message.
  > 
  > More text in commit message.
  > --- confuse the diff detection
  > 
  > diff --git a/x b/x
  > new file mode 100644
  > --- /dev/null
  > +++ b/x
  > @@ -0,0 +1,1 @@
  > +new file
  > Text after patch.
  > 
  > EOF
  adding email to series file
  applying email
  now at: email

hg tip -v

  $ hg tip -v
  changeset:   0:1a706973a7d8
  tag:         email
  tag:         qbase
  tag:         qtip
  tag:         tip
  user:        Username in patch <[e-mail]>
  date:        Thu Jan 01 00:00:00 1970 +0000
  files:       x
  description:
  First line of commit message.
  
  More text in commit message.
  
  
  $ hg qpop
  popping email
  patch queue now empty
  $ hg qdelete email

import URL

  $ echo foo >> foo
  $ hg add foo
  $ hg diff > url.diff
  $ hg revert --no-backup foo
  $ rm foo

Under unix: file:///foobar/blah
Under windows: file:///c:/foobar/blah

  $ patchurl=`pwd | tr '\\\\' /`/url.diff
  $ expr "$patchurl" : "\/" > /dev/null || patchurl="/$patchurl"
  $ hg qimport file://"$patchurl"
  adding url.diff to series file
  $ rm url.diff
  $ hg qun
  url.diff

import patch that already exists

  $ echo foo2 >> foo
  $ hg add foo
  $ hg diff > ../url.diff
  $ hg revert --no-backup foo
  $ rm foo
  $ hg qimport ../url.diff
  abort: patch "url.diff" already exists
  [255]
  $ hg qpush
  applying url.diff
  now at: url.diff
  $ cat foo
  foo
  $ hg qpop
  popping url.diff
  patch queue now empty

qimport -f

  $ hg qimport -f ../url.diff
  adding url.diff to series file
  $ hg qpush
  applying url.diff
  now at: url.diff
  $ cat foo
  foo2
  $ hg qpop
  popping url.diff
  patch queue now empty

build diff with CRLF

  $ python ../writelines.py b 5 'a\n' 5 'a\r\n'
  $ hg ci -Am addb
  adding b
  $ python ../writelines.py b 2 'a\n' 10 'b\n' 2 'a\r\n'
  $ hg diff > b.diff
  $ hg up -C
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

qimport CRLF diff

  $ hg qimport b.diff
  adding b.diff to series file
  $ hg qpush
  applying b.diff
  now at: b.diff

try to import --push

  $ cat > appendfoo.diff <<EOF
  > append foo
  > 
  > diff -r 07f494440405 -r 261500830e46 baz
  > --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  > +++ b/baz	Thu Jan 01 00:00:00 1970 +0000
  > @@ -0,0 +1,1 @@
  > +foo
  > EOF

  $ cat > appendbar.diff <<EOF
  > append bar
  > 
  > diff -r 07f494440405 -r 261500830e46 baz
  > --- a/baz	Thu Jan 01 00:00:00 1970 +0000
  > +++ b/baz	Thu Jan 01 00:00:00 1970 +0000
  > @@ -1,1 +1,2 @@
  >  foo
  > +bar
  > EOF

  $ hg qimport --push appendfoo.diff appendbar.diff
  adding appendfoo.diff to series file
  adding appendbar.diff to series file
  applying appendfoo.diff
  applying appendbar.diff
  now at: appendbar.diff
  $ hg qfin -a
  patch b.diff finalized without changeset message
  $ touch .hg/patches/2.diff
  $ hg qimport -r 'p1(.)::'
  abort: patch "2.diff" already exists
  [255]
  $ hg qapplied
  3.diff
  $ hg qfin -a
  $ rm .hg/patches/2.diff
  $ hg qimport -r 'p1(.)::' -P
  $ hg qpop -a
  popping 3.diff
  popping 2.diff
  patch queue now empty
  $ hg qdel 3.diff
  $ hg qdel -k 2.diff

qimport -e

  $ hg qimport -e 2.diff
  adding 2.diff to series file
  $ hg qdel -k 2.diff

qimport -e --name newname oldexisitingpatch

  $ hg qimport -e --name this-name-is-better 2.diff
  renaming 2.diff to this-name-is-better
  adding this-name-is-better to series file
  $ hg qser
  this-name-is-better
  url.diff

qimport -e --name without --force

  $ cp .hg/patches/this-name-is-better .hg/patches/3.diff
  $ hg qimport -e --name this-name-is-better 3.diff
  abort: patch "this-name-is-better" already exists
  [255]
  $ hg qser
  this-name-is-better
  url.diff

qimport -e --name with --force

  $ hg qimport --force -e --name this-name-is-better 3.diff
  renaming 3.diff to this-name-is-better
  adding this-name-is-better to series file
  $ hg qser
  this-name-is-better
  url.diff

qimport with bad name, should abort before reading file

  $ hg qimport non-existent-file --name .hg
  abort: patch name cannot begin with ".hg"
  [255]

qimport http:// patch with leading slashes in url

set up hgweb

  $ cd ..
  $ hg init served
  $ cd served
  $ echo a > a
  $ hg ci -Am patch
  adding a
  $ hg serve -p $HGPORT -d --pid-file=hg.pid -A access.log -E errors.log
  $ cat hg.pid >> $DAEMON_PIDS

  $ cd ../repo
  $ hg qimport http://localhost:$HGPORT/raw-rev/0///
  adding 0 to series file

check qimport phase:

  $ hg -q qpush
  now at: 0
  $ hg phase qparent
  1: draft
  $ hg qimport -r qparent
  $ hg phase qbase
  1: draft
  $ hg qfinish qbase
  $ echo '[mq]' >> $HGRCPATH
  $ echo 'secret=true' >> $HGRCPATH
  $ hg qimport -r qparent
  $ hg phase qbase
  1: secret

  $ cd ..

  $ killdaemons.py