view tests/test-mq-qfold.t @ 30442:41a8106789ca

util: implement zstd compression engine Now that zstd is vendored and being built (in some configurations), we can implement a compression engine for zstd! The zstd engine is a little different from existing engines. Because it may not always be present, we have to defer load the module in case importing it fails. We facilitate this via a cached property that holds a reference to the module or None. The "available" method is implemented to reflect reality. The zstd engine declares its ability to handle bundles using the "zstd" human name and the "ZS" internal name. The latter was chosen because internal names are 2 characters (by only convention I think) and "ZS" seems reasonable. The engine, like others, supports specifying the compression level. However, there are no consumers of this API that yet pass in that argument. I have plans to change that, so stay tuned. Since all we need to do to support bundle generation with a new compression engine is implement and register the compression engine, bundle generation with zstd "just works!" Tests demonstrating this have been added. How does performance of zstd for bundle generation compare? On the mozilla-unified repo, `hg bundle --all -t <engine>-v2` yields the following on my i7-6700K on Linux: engine CPU time bundle size vs orig size throughput none 97.0s 4,054,405,584 100.0% 41.8 MB/s bzip2 (l=9) 393.6s 975,343,098 24.0% 10.3 MB/s gzip (l=6) 184.0s 1,140,533,074 28.1% 22.0 MB/s zstd (l=1) 108.2s 1,119,434,718 27.6% 37.5 MB/s zstd (l=2) 111.3s 1,078,328,002 26.6% 36.4 MB/s zstd (l=3) 113.7s 1,011,823,727 25.0% 35.7 MB/s zstd (l=4) 116.0s 1,008,965,888 24.9% 35.0 MB/s zstd (l=5) 121.0s 977,203,148 24.1% 33.5 MB/s zstd (l=6) 131.7s 927,360,198 22.9% 30.8 MB/s zstd (l=7) 139.0s 912,808,505 22.5% 29.2 MB/s zstd (l=12) 198.1s 854,527,714 21.1% 20.5 MB/s zstd (l=18) 681.6s 789,750,690 19.5% 5.9 MB/s On compression, zstd for bundle generation delivers: * better compression than gzip with significantly less CPU utilization * better than bzip2 compression ratios while still being significantly faster than gzip * ability to aggressively tune compression level to achieve significantly smaller bundles That last point is important. With clone bundles, a server can pre-generate a bundle file, upload it to a static file server, and redirect clients to transparently download it during clone. The server could choose to produce a zstd bundle with the highest compression settings possible. This would take a very long time - a magnitude longer than a typical zstd bundle generation - but the result would be hundreds of megabytes smaller! For the clone volume we do at Mozilla, this could translate to petabytes of bandwidth savings per year and faster clones (due to smaller transfer size). I don't have detailed numbers to report on decompression. However, zstd decompression is fast: >1 GB/s output throughput on this machine, even through the Python bindings. And it can do that regardless of the compression level of the input. By the time you have enough data to worry about overhead of decompression, you have plenty of other things to worry about performance wise. zstd is wins all around. I can't wait to implement support for it on the wire protocol and in revlogs.
author Gregory Szorc <gregory.szorc@gmail.com>
date Fri, 11 Nov 2016 01:10:07 -0800
parents 3633403888ae
children c6d31e659a28
line wrap: on
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  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > mq =
  > [mq]
  > git = keep
  > [diff]
  > nodates = 1
  > EOF

init:

  $ hg init repo
  $ cd repo
  $ echo a > a
  $ hg ci -Am adda
  adding a
  $ echo a >> a
  $ hg qnew -f p1
  $ echo b >> a
  $ hg qnew -f p2
  $ echo c >> a
  $ hg qnew -f p3

Fold in the middle of the queue:
(this tests also that editor is not invoked if '--edit' is not
specified)

  $ hg qpop p1
  popping p3
  popping p2
  now at: p1

  $ hg qdiff
  diff -r 07f494440405 a
  --- a/a
  +++ b/a
  @@ -1,1 +1,2 @@
   a
  +a

  $ HGEDITOR=cat hg qfold p2
  $ grep git .hg/patches/p1 && echo 'git patch found!'
  [1]

  $ hg qser
  p1
  p3

  $ hg qdiff
  diff -r 07f494440405 a
  --- a/a
  +++ b/a
  @@ -1,1 +1,3 @@
   a
  +a
  +b

Fold with local changes:

  $ echo d >> a
  $ hg qfold p3
  abort: local changes found, qrefresh first
  [255]

  $ hg diff -c .
  diff -r 07f494440405 -r ???????????? a (glob)
  --- a/a
  +++ b/a
  @@ -1,1 +1,3 @@
   a
  +a
  +b

  $ hg revert -a --no-backup
  reverting a

Fold git patch into a regular patch, expect git patch:

  $ echo a >> a
  $ hg qnew -f regular
  $ hg cp a aa
  $ hg qnew --git -f git

  $ hg qpop
  popping git
  now at: regular

  $ hg qfold git

  $ cat .hg/patches/regular
  # HG changeset patch
  # Parent  ???????????????????????????????????????? (glob)
  
  diff --git a/a b/a
  --- a/a
  +++ b/a
  @@ -1,3 +1,4 @@
   a
   a
   b
  +a
  diff --git a/a b/aa
  copy from a
  copy to aa
  --- a/a
  +++ b/aa
  @@ -1,3 +1,4 @@
   a
   a
   b
  +a

  $ hg qpop
  popping regular
  now at: p1

  $ hg qdel regular

Fold regular patch into a git patch, expect git patch:

  $ hg cp a aa
  $ hg qnew --git -f git
  $ echo b >> aa
  $ hg qnew -f regular

  $ hg qpop
  popping regular
  now at: git

  $ hg qfold regular

  $ cat .hg/patches/git
  # HG changeset patch
  # Parent  ???????????????????????????????????????? (glob)
  
  diff --git a/a b/aa
  copy from a
  copy to aa
  --- a/a
  +++ b/aa
  @@ -1,3 +1,4 @@
   a
   a
   b
  +b

Test saving last-message.txt:

  $ hg qrefresh -m "original message"

  $ cat > $TESTTMP/commitfailure.py <<EOF
  > from mercurial import error
  > def reposetup(ui, repo):
  >     class commitfailure(repo.__class__):
  >         def commit(self, *args, **kwargs):
  >             raise error.Abort('emulating unexpected abort')
  >     repo.__class__ = commitfailure
  > EOF

  $ cat >> .hg/hgrc <<EOF
  > [extensions]
  > # this failure occurs before editor invocation
  > commitfailure = $TESTTMP/commitfailure.py
  > EOF

  $ cat > $TESTTMP/editor.sh << EOF
  > echo "==== before editing"
  > cat \$1
  > echo "===="
  > (echo; echo "test saving last-message.txt") >> \$1
  > EOF

  $ hg qapplied
  p1
  git
  $ hg tip --template "{files}\n"
  aa

(test that editor is not invoked before transaction starting,
and that combination of '--edit' and '--message' doesn't abort execution)

  $ rm -f .hg/last-message.txt
  $ HGEDITOR="sh $TESTTMP/editor.sh" hg qfold -e -m MESSAGE p3
  qrefresh interrupted while patch was popped! (revert --all, qpush to recover)
  abort: emulating unexpected abort
  [255]
  $ test -f .hg/last-message.txt
  [1]

(reset applied patches and directory status)

  $ cat >> .hg/hgrc <<EOF
  > [extensions]
  > # this failure occurs after editor invocation
  > commitfailure = !
  > EOF

  $ hg qapplied
  p1
  $ hg status -A aa
  ? aa
  $ rm aa
  $ hg status -m
  M a
  $ hg revert --no-backup -q a
  $ hg qpush -q git
  now at: git

(test that editor is invoked and commit message is saved into
"last-message.txt")

  $ cat >> .hg/hgrc <<EOF
  > [hooks]
  > # this failure occurs after editor invocation
  > pretxncommit.unexpectedabort = false
  > EOF

  $ rm -f .hg/last-message.txt
  $ HGEDITOR="sh $TESTTMP/editor.sh" hg qfold -e p3
  ==== before editing
  original message
  
  
  HG: Enter commit message.  Lines beginning with 'HG:' are removed.
  HG: Leave message empty to use default message.
  HG: --
  HG: user: test
  HG: branch 'default'
  HG: added aa
  HG: changed a
  ====
  note: commit message saved in .hg/last-message.txt
  transaction abort!
  rollback completed
  qrefresh interrupted while patch was popped! (revert --all, qpush to recover)
  abort: pretxncommit.unexpectedabort hook exited with status 1
  [255]
  $ cat .hg/last-message.txt
  original message
  
  
  
  test saving last-message.txt

(confirm whether files listed up in the commit message editing are correct)

  $ cat >> .hg/hgrc <<EOF
  > [hooks]
  > pretxncommit.unexpectedabort =
  > EOF
  $ hg status -u | while read f; do rm ${f}; done
  $ hg revert --no-backup -q --all
  $ hg qpush -q git
  now at: git
  $ hg qpush -q --move p3
  now at: p3

  $ hg status --rev "git^1" --rev . -arm
  M a
  A aa

  $ cd ..