tests/test-init.t

revlog: use an LRU cache for delta chain bases

Profiling using statprof revealed a hotspot during changegroup
application calculating delta chain bases on generaldelta repos.
Essentially, revlog._addrevision() was performing a lot of redundant
work tracing the delta chain as part of determining when the chain
distance was acceptable. This was most pronounced when adding
revisions to manifests, which can have delta chains thousands of
revisions long.

There was a delta chain base cache on revlogs before, but it only
captured a single revision. This was acceptable before generaldelta,
when _addrevision would build deltas from the previous revision and
thus we'd pretty much guarantee a cache hit when resolving the delta
chain base on a subsequent _addrevision call. However, it isn't
suitable for generaldelta because parent revisions aren't necessarily
the last processed revision.

This patch converts the delta chain base cache to an LRU dict cache.
The cache can hold multiple entries, so generaldelta repos have a
higher chance of getting a cache hit.

The impact of this change when processing changegroup additions is
significant. On a generaldelta conversion of the "mozilla-unified"
repo (which contains heads of the main Firefox repositories in
chronological order - this means there are lots of transitions between
heads in revlog order), this change has the following impact when
performing an `hg unbundle` of an uncompressed bundle of the repo:

before: 5:42 CPU time
after:  4:34 CPU time

Most of this time is saved when applying the changelog and manifest
revlogs:

before: 2:30 CPU time
after:  1:17 CPU time

That nearly a 50% reduction in CPU time applying changesets and
manifests!

Applying a gzipped bundle of the same repo (effectively simulating a
`hg clone` over HTTP) showed a similar speedup:

before: 5:53 CPU time
after:  4:46 CPU time

Wall time improvements were basically the same as CPU time.

I didn't measure explicitly, but it feels like most of the time
is saved when processing manifests. This makes sense, as large
manifests tend to have very long delta chains and thus benefit the
most from this cache.

So, this change effectively makes changegroup application (which is
used by `hg unbundle`, `hg clone`, `hg pull`, `hg unshelve`, and
various other commands) significantly faster when delta chains are
long (which can happen on repos with large numbers of files and thus
large manifests).

In theory, this change can result in more memory utilization. However,
we're caching a dict of ints. At most we have 200 ints + Python object
overhead per revlog. And, the cache is really only populated when
performing read-heavy operations, such as adding changegroups or
scanning an individual revlog. For memory bloat to be an issue, we'd
need to scan/read several revisions from several revlogs all while
having active references to several revlogs. I don't think there are
many operations that do this, so I don't think memory bloat from the
cache will be an issue.

This test tries to exercise the ssh functionality with a dummy script

(enable general delta early)

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

  $ checknewrepo()
  > {
  >    name=$1
  >    if [ -d "$name"/.hg/store ]; then
  >    echo store created
  >    fi
  >    if [ -f "$name"/.hg/00changelog.i ]; then
  >    echo 00changelog.i created
  >    fi
  >    cat "$name"/.hg/requires
  > }

creating 'local'

  $ hg init local
  $ checknewrepo local
  store created
  00changelog.i created
  dotencode
  fncache
  generaldelta
  revlogv1
  store
  $ echo this > local/foo
  $ hg ci --cwd local -A -m "init"
  adding foo

test custom revlog chunk cache sizes

  $ hg --config format.chunkcachesize=0 log -R local -pv
  abort: revlog chunk cache size 0 is not greater than 0!
  [255]
  $ hg --config format.chunkcachesize=1023 log -R local -pv
  abort: revlog chunk cache size 1023 is not a power of 2!
  [255]
  $ hg --config format.chunkcachesize=1024 log -R local -pv
  changeset:   0:08b9e9f63b32
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  files:       foo
  description:
  init
  
  
  diff -r 000000000000 -r 08b9e9f63b32 foo
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/foo	Thu Jan 01 00:00:00 1970 +0000
  @@ -0,0 +1,1 @@
  +this
  

creating repo with format.usestore=false

  $ hg --config format.usestore=false init old
  $ checknewrepo old
  generaldelta
  revlogv1

creating repo with format.usefncache=false

  $ hg --config format.usefncache=false init old2
  $ checknewrepo old2
  store created
  00changelog.i created
  generaldelta
  revlogv1
  store

creating repo with format.dotencode=false

  $ hg --config format.dotencode=false init old3
  $ checknewrepo old3
  store created
  00changelog.i created
  fncache
  generaldelta
  revlogv1
  store

creating repo with format.dotencode=false

  $ hg --config format.generaldelta=false --config format.usegeneraldelta=false init old4
  $ checknewrepo old4
  store created
  00changelog.i created
  dotencode
  fncache
  revlogv1
  store

test failure

  $ hg init local
  abort: repository local already exists!
  [255]

init+push to remote2

  $ hg init -e "python \"$TESTDIR/dummyssh\"" ssh://user@dummy/remote2
  $ hg incoming -R remote2 local
  comparing with local
  changeset:   0:08b9e9f63b32
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     init
  

  $ hg push -R local -e "python \"$TESTDIR/dummyssh\"" ssh://user@dummy/remote2
  pushing to ssh://user@dummy/remote2
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 1 changesets with 1 changes to 1 files

clone to remote1

  $ hg clone -e "python \"$TESTDIR/dummyssh\"" local ssh://user@dummy/remote1
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 1 changesets with 1 changes to 1 files

The largefiles extension doesn't crash
  $ hg clone -e "python \"$TESTDIR/dummyssh\"" local ssh://user@dummy/remotelf --config extensions.largefiles=
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 1 changesets with 1 changes to 1 files

init to existing repo

  $ hg init -e "python \"$TESTDIR/dummyssh\"" ssh://user@dummy/remote1
  abort: repository remote1 already exists!
  abort: could not create remote repo!
  [255]

clone to existing repo

  $ hg clone -e "python \"$TESTDIR/dummyssh\"" local ssh://user@dummy/remote1
  abort: repository remote1 already exists!
  abort: could not create remote repo!
  [255]

output of dummyssh

  $ cat dummylog
  Got arguments 1:user@dummy 2:hg init remote2
  Got arguments 1:user@dummy 2:hg -R remote2 serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote2 serve --stdio
  Got arguments 1:user@dummy 2:hg init remote1
  Got arguments 1:user@dummy 2:hg -R remote1 serve --stdio
  Got arguments 1:user@dummy 2:hg init remotelf
  Got arguments 1:user@dummy 2:hg -R remotelf serve --stdio
  Got arguments 1:user@dummy 2:hg init remote1
  Got arguments 1:user@dummy 2:hg init remote1

comparing repositories

  $ hg tip -q -R local
  0:08b9e9f63b32
  $ hg tip -q -R remote1
  0:08b9e9f63b32
  $ hg tip -q -R remote2
  0:08b9e9f63b32

check names for repositories (clashes with URL schemes, special chars)

  $ for i in bundle file hg http https old-http ssh static-http "with space"; do
  >   printf "hg init \"$i\"... "
  >   hg init "$i"
  >   test -d "$i" -a -d "$i/.hg" && echo "ok" || echo "failed"
  > done
  hg init "bundle"... ok
  hg init "file"... ok
  hg init "hg"... ok
  hg init "http"... ok
  hg init "https"... ok
  hg init "old-http"... ok
  hg init "ssh"... ok
  hg init "static-http"... ok
  hg init "with space"... ok
#if eol-in-paths
/* " " is not a valid name for a directory on Windows */
  $ hg init " "
  $ test -d " "
  $ test -d " /.hg"
#endif

creating 'local/sub/repo'

  $ hg init local/sub/repo
  $ checknewrepo local/sub/repo
  store created
  00changelog.i created
  dotencode
  fncache
  generaldelta
  revlogv1
  store

prepare test of init of url configured from paths

  $ echo '[paths]' >> $HGRCPATH
  $ echo "somewhere = `pwd`/url from paths" >> $HGRCPATH
  $ echo "elsewhere = `pwd`/another paths url" >> $HGRCPATH

init should (for consistency with clone) expand the url

  $ hg init somewhere
  $ checknewrepo "url from paths"
  store created
  00changelog.i created
  dotencode
  fncache
  generaldelta
  revlogv1
  store

verify that clone also expand urls

  $ hg clone somewhere elsewhere
  updating to branch default
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ checknewrepo "another paths url"
  store created
  00changelog.i created
  dotencode
  fncache
  generaldelta
  revlogv1
  store

clone bookmarks

  $ hg -R local bookmark test
  $ hg -R local bookmarks
   * test                      0:08b9e9f63b32
  $ hg clone -e "python \"$TESTDIR/dummyssh\"" local ssh://user@dummy/remote-bookmarks
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 1 changesets with 1 changes to 1 files
  exporting bookmark test
  $ hg -R remote-bookmarks bookmarks
     test                      0:08b9e9f63b32