view tests/test-bundle-type.t @ 34824:e2ad93bcc084

revlog: introduce an experimental flag to slice chunks reads when too sparse

Delta chains can become quite sparse if there is a lot of unrelated data between
relevant pieces. Right now, revlog always reads all the necessary data for the
delta chain in one single read. This can lead to a lot of unrelated data to be
read (see issue5482 for more details).
One can use the `experimental.maxdeltachainspan` option with a large value
(or -1) to easily produce a very sparse delta chain.

This change introduces the ability to slice the chunks retrieval into  multiple
reads, skipping large sections of unrelated data. Preliminary testing shows
interesting results. For example the peak memory consumption to read a manifest
on a large repository is reduced from 600MB to 250MB (200MB without
maxdeltachainspan). However, the slicing itself and the multiple reads can have
an negative impact on performance. This is why the new feature is hidden behind
an experimental flag.

Future changesets will add various parameters to control the slicing heuristics.
We hope to experiment a wide variety of repositories during 4.4 and hopefully
turn the feature on by default in 4.5.
As a first try, the algorithm itself is prone to deep changes. However, we wish
to define APIs and have a baseline to work on.

  $ cat << EOF >> $HGRCPATH
  > [format]
  > usegeneraldelta=yes
  > EOF

bundle w/o type option

  $ hg init t1
  $ hg init t2
  $ cd t1
  $ echo blablablablabla > file.txt
  $ hg ci -Ama
  adding file.txt
  $ hg log | grep summary
  summary:     a
  $ hg bundle ../b1 ../t2
  searching for changes
  1 changesets found

  $ cd ../t2
  $ hg pull ../b1
  pulling from ../b1
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets c35a0f9217e6
  (run 'hg update' to get a working copy)
  $ hg up
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg log | grep summary
  summary:     a
  $ cd ..

Unknown compression type is rejected

  $ hg init t3
  $ cd t3
  $ hg -q pull ../b1
  $ hg bundle -a -t unknown out.hg
  abort: unknown is not a recognized bundle specification
  (see 'hg help bundlespec' for supported values for --type)
  [255]

  $ hg bundle -a -t unknown-v2 out.hg
  abort: unknown compression is not supported
  (see 'hg help bundlespec' for supported values for --type)
  [255]

  $ cd ..

test bundle types

  $ testbundle() {
  >   echo % test bundle type $1
  >   hg init t$1
  >   cd t1
  >   hg bundle -t $1 ../b$1 ../t$1
  >   f -q -B6 -D ../b$1; echo
  >   cd ../t$1
  >   hg debugbundle ../b$1
  >   hg debugbundle --spec ../b$1
  >   echo
  >   cd ..
  > }

  $ for t in "None" "bzip2" "gzip" "none-v2" "v2" "v1" "gzip-v1"; do
  >   testbundle $t
  > done
  % test bundle type None
  searching for changes
  1 changesets found
  HG20\x00\x00 (esc)
  Stream params: {}
  changegroup -- {nbchanges: 1, version: 02}
      c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
  none-v2
  
  % test bundle type bzip2
  searching for changes
  1 changesets found
  HG20\x00\x00 (esc)
  Stream params: {Compression: BZ}
  changegroup -- {nbchanges: 1, version: 02}
      c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
  bzip2-v2
  
  % test bundle type gzip
  searching for changes
  1 changesets found
  HG20\x00\x00 (esc)
  Stream params: {Compression: GZ}
  changegroup -- {nbchanges: 1, version: 02}
      c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
  gzip-v2
  
  % test bundle type none-v2
  searching for changes
  1 changesets found
  HG20\x00\x00 (esc)
  Stream params: {}
  changegroup -- {nbchanges: 1, version: 02}
      c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
  none-v2
  
  % test bundle type v2
  searching for changes
  1 changesets found
  HG20\x00\x00 (esc)
  Stream params: {Compression: BZ}
  changegroup -- {nbchanges: 1, version: 02}
      c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
  bzip2-v2
  
  % test bundle type v1
  searching for changes
  1 changesets found
  HG10BZ
  c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
  bzip2-v1
  
  % test bundle type gzip-v1
  searching for changes
  1 changesets found
  HG10GZ
  c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
  gzip-v1
  

Compression level can be adjusted for bundle2 bundles

  $ hg init test-complevel
  $ cd test-complevel

  $ cat > file0 << EOF
  > this is a file
  > with some text
  > and some more text
  > and other content
  > EOF
  $ cat > file1 << EOF
  > this is another file
  > with some other content
  > and repeated, repeated, repeated, repeated content
  > EOF
  $ hg -q commit -A -m initial

  $ hg bundle -a -t gzip-v2 gzip-v2.hg
  1 changesets found
  $ f --size gzip-v2.hg
  gzip-v2.hg: size=427

  $ hg --config experimental.bundlecomplevel=1 bundle -a -t gzip-v2 gzip-v2-level1.hg
  1 changesets found
  $ f --size gzip-v2-level1.hg
  gzip-v2-level1.hg: size=435

  $ cd ..

#if zstd

  $ for t in "zstd" "zstd-v2"; do
  >   testbundle $t
  > done
  % test bundle type zstd
  searching for changes
  1 changesets found
  HG20\x00\x00 (esc)
  Stream params: {Compression: ZS}
  changegroup -- {nbchanges: 1, version: 02}
      c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
  zstd-v2
  
  % test bundle type zstd-v2
  searching for changes
  1 changesets found
  HG20\x00\x00 (esc)
  Stream params: {Compression: ZS}
  changegroup -- {nbchanges: 1, version: 02}
      c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
  zstd-v2
  

Explicit request for zstd on non-generaldelta repos

  $ hg --config format.usegeneraldelta=false init nogd
  $ hg -q -R nogd pull t1
  $ hg -R nogd bundle -a -t zstd nogd-zstd
  1 changesets found

zstd-v1 always fails

  $ hg -R tzstd bundle -a -t zstd-v1 zstd-v1
  abort: compression engine zstd is not supported on v1 bundles
  (see 'hg help bundlespec' for supported values for --type)
  [255]

#else

zstd is a valid engine but isn't available

  $ hg -R t1 bundle -a -t zstd irrelevant.hg
  abort: compression engine zstd could not be loaded
  [255]

#endif

test garbage file

  $ echo garbage > bgarbage
  $ hg init tgarbage
  $ cd tgarbage
  $ hg pull ../bgarbage
  pulling from ../bgarbage
  abort: ../bgarbage: not a Mercurial bundle
  [255]
  $ cd ..

test invalid bundle type

  $ cd t1
  $ hg bundle -a -t garbage ../bgarbage
  abort: garbage is not a recognized bundle specification
  (see 'hg help bundlespec' for supported values for --type)
  [255]
  $ cd ..