view tests/test-treediscovery.t @ 29830:92ac2baaea86

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.

#require killdaemons

Tests discovery against servers without getbundle support:

  $ CAP="getbundle bundle2"
  $ . "$TESTDIR/notcapable"
  $ cat >> $HGRCPATH <<EOF
  > [ui]
  > logtemplate="{rev} {node|short}: {desc} {branches}\n"
  > EOF

Setup HTTP server control:

  $ remote=http://localhost:$HGPORT/
  $ export remote
  $ tstart() {
  >   echo '[web]' > $1/.hg/hgrc
  >   echo 'push_ssl = false' >> $1/.hg/hgrc
  >   echo 'allow_push = *' >> $1/.hg/hgrc
  >   hg serve -R $1 -p $HGPORT -d --pid-file=hg.pid -A access.log -E errors.log
  >   cat hg.pid >> $DAEMON_PIDS
  > }
  $ tstop() {
  >   killdaemons.py
  >   [ "$1" ] && cut -d' ' -f6- access.log && cat errors.log
  >   rm access.log errors.log
  > }

Both are empty:

  $ hg init empty1
  $ hg init empty2
  $ tstart empty2
  $ hg incoming -R empty1 $remote
  comparing with http://localhost:$HGPORT/
  no changes found
  [1]
  $ hg outgoing -R empty1 $remote
  comparing with http://localhost:$HGPORT/
  no changes found
  [1]
  $ hg pull -R empty1 $remote
  pulling from http://localhost:$HGPORT/
  no changes found
  $ hg push -R empty1 $remote
  pushing to http://localhost:$HGPORT/
  no changes found
  [1]
  $ tstop

Base repo:

  $ hg init main
  $ cd main
  $ hg debugbuilddag -mo '+2:tbase @name1 +3:thead1 <tbase @name2 +4:thead2 @both /thead1 +2:tmaintip'
  $ hg log -G
  o  11 a19bfa7e7328: r11 both
  |
  o  10 8b6bad1512e1: r10 both
  |
  o    9 025829e08038: r9 both
  |\
  | o  8 d8f638ac69e9: r8 name2
  | |
  | o  7 b6b4d315a2ac: r7 name2
  | |
  | o  6 6c6f5d5f3c11: r6 name2
  | |
  | o  5 70314b29987d: r5 name2
  | |
  o |  4 e71dbbc70e03: r4 name1
  | |
  o |  3 2c8d5d5ec612: r3 name1
  | |
  o |  2 a7892891da29: r2 name1
  |/
  o  1 0019a3b924fd: r1
  |
  o  0 d57206cc072a: r0
  
  $ cd ..
  $ tstart main

Full clone:

  $ hg clone main full
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd full
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ hg outgoing $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ hg pull $remote
  pulling from http://localhost:$HGPORT/
  searching for changes
  no changes found
  $ hg push $remote
  pushing to http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ cd ..

Local is empty:

  $ cd empty1
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  0 d57206cc072a: r0 
  1 0019a3b924fd: r1 
  2 a7892891da29: r2 name1
  3 2c8d5d5ec612: r3 name1
  4 e71dbbc70e03: r4 name1
  5 70314b29987d: r5 name2
  6 6c6f5d5f3c11: r6 name2
  7 b6b4d315a2ac: r7 name2
  8 d8f638ac69e9: r8 name2
  9 025829e08038: r9 both
  10 8b6bad1512e1: r10 both
  11 a19bfa7e7328: r11 both
  $ hg outgoing $remote
  comparing with http://localhost:$HGPORT/
  no changes found
  [1]
  $ hg push $remote
  pushing to http://localhost:$HGPORT/
  no changes found
  [1]
  $ hg pull $remote
  pulling from http://localhost:$HGPORT/
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 12 changesets with 24 changes to 2 files
  (run 'hg update' to get a working copy)
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ cd ..

Local is subset:

  $ hg clone main subset --rev name2 ; cd subset
  adding changesets
  adding manifests
  adding file changes
  added 6 changesets with 12 changes to 2 files
  updating to branch name2
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  6 a7892891da29: r2 name1
  7 2c8d5d5ec612: r3 name1
  8 e71dbbc70e03: r4 name1
  9 025829e08038: r9 both
  10 8b6bad1512e1: r10 both
  11 a19bfa7e7328: r11 both
  $ hg outgoing $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ hg push $remote
  pushing to http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ hg pull $remote
  pulling from http://localhost:$HGPORT/
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 6 changesets with 12 changes to 2 files
  (run 'hg update' to get a working copy)
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ cd ..
  $ tstop

Remote is empty:

  $ tstart empty2
  $ cd main
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ hg outgoing $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  0 d57206cc072a: r0 
  1 0019a3b924fd: r1 
  2 a7892891da29: r2 name1
  3 2c8d5d5ec612: r3 name1
  4 e71dbbc70e03: r4 name1
  5 70314b29987d: r5 name2
  6 6c6f5d5f3c11: r6 name2
  7 b6b4d315a2ac: r7 name2
  8 d8f638ac69e9: r8 name2
  9 025829e08038: r9 both
  10 8b6bad1512e1: r10 both
  11 a19bfa7e7328: r11 both
  $ hg pull $remote
  pulling from http://localhost:$HGPORT/
  searching for changes
  no changes found
  $ hg push $remote
  pushing to http://localhost:$HGPORT/
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 12 changesets with 24 changes to 2 files
  $ hg outgoing $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ cd ..
  $ tstop

Local is superset:

  $ hg clone main subset2 --rev name2
  adding changesets
  adding manifests
  adding file changes
  added 6 changesets with 12 changes to 2 files
  updating to branch name2
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ tstart subset2
  $ cd main
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ hg outgoing $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  2 a7892891da29: r2 name1
  3 2c8d5d5ec612: r3 name1
  4 e71dbbc70e03: r4 name1
  9 025829e08038: r9 both
  10 8b6bad1512e1: r10 both
  11 a19bfa7e7328: r11 both
  $ hg pull $remote
  pulling from http://localhost:$HGPORT/
  searching for changes
  no changes found
  $ hg push $remote
  pushing to http://localhost:$HGPORT/
  searching for changes
  abort: push creates new remote branches: both, name1!
  (use 'hg push --new-branch' to create new remote branches)
  [255]
  $ hg push $remote --new-branch
  pushing to http://localhost:$HGPORT/
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 6 changesets with 12 changes to 2 files
  $ hg outgoing $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ cd ..
  $ tstop

Partial pull:

  $ tstart main
  $ hg clone $remote partial --rev name2
  adding changesets
  adding manifests
  adding file changes
  added 6 changesets with 12 changes to 2 files
  updating to branch name2
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd partial
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  6 a7892891da29: r2 name1
  7 2c8d5d5ec612: r3 name1
  8 e71dbbc70e03: r4 name1
  9 025829e08038: r9 both
  10 8b6bad1512e1: r10 both
  11 a19bfa7e7328: r11 both
  $ hg incoming $remote --rev name1
  comparing with http://localhost:$HGPORT/
  searching for changes
  6 a7892891da29: r2 name1
  7 2c8d5d5ec612: r3 name1
  8 e71dbbc70e03: r4 name1
  $ hg pull $remote --rev name1
  pulling from http://localhost:$HGPORT/
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 6 changes to 2 files (+1 heads)
  (run 'hg heads' to see heads)
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  9 025829e08038: r9 both
  10 8b6bad1512e1: r10 both
  11 a19bfa7e7328: r11 both
  $ cd ..
  $ tstop

Both have new stuff in new named branches:

  $ hg clone main repo1a --rev name1 -q
  $ hg clone repo1a repo1b -q
  $ hg clone main repo2a --rev name2 -q
  $ hg clone repo2a repo2b -q
  $ tstart repo1a

  $ cd repo2a
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  6 a7892891da29: r2 name1
  7 2c8d5d5ec612: r3 name1
  8 e71dbbc70e03: r4 name1
  $ hg outgoing $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  2 70314b29987d: r5 name2
  3 6c6f5d5f3c11: r6 name2
  4 b6b4d315a2ac: r7 name2
  5 d8f638ac69e9: r8 name2
  $ hg push $remote --new-branch
  pushing to http://localhost:$HGPORT/
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 4 changesets with 8 changes to 2 files (+1 heads)
  $ hg pull $remote
  pulling from http://localhost:$HGPORT/
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 6 changes to 2 files (+1 heads)
  (run 'hg heads' to see heads)
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ hg outgoing $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ cd ..
  $ tstop

  $ tstart repo1b
  $ cd repo2b
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  6 a7892891da29: r2 name1
  7 2c8d5d5ec612: r3 name1
  8 e71dbbc70e03: r4 name1
  $ hg outgoing $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  2 70314b29987d: r5 name2
  3 6c6f5d5f3c11: r6 name2
  4 b6b4d315a2ac: r7 name2
  5 d8f638ac69e9: r8 name2
  $ hg pull $remote
  pulling from http://localhost:$HGPORT/
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 6 changes to 2 files (+1 heads)
  (run 'hg heads' to see heads)
  $ hg push $remote --new-branch
  pushing to http://localhost:$HGPORT/
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 4 changesets with 8 changes to 2 files (+1 heads)
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ hg outgoing $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ cd ..
  $ tstop

Both have new stuff in existing named branches:

  $ rm -r repo1a repo1b repo2a repo2b
  $ hg clone main repo1a --rev 3 --rev 8 -q
  $ hg clone repo1a repo1b -q
  $ hg clone main repo2a --rev 4 --rev 7 -q
  $ hg clone repo2a repo2b -q
  $ tstart repo1a

  $ cd repo2a
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  8 d8f638ac69e9: r8 name2
  $ hg outgoing $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  4 e71dbbc70e03: r4 name1
  $ hg push $remote --new-branch
  pushing to http://localhost:$HGPORT/
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 1 changesets with 2 changes to 2 files
  $ hg pull $remote
  pulling from http://localhost:$HGPORT/
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 2 changes to 2 files
  (run 'hg update' to get a working copy)
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ hg outgoing $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ cd ..
  $ tstop

  $ tstart repo1b
  $ cd repo2b
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  8 d8f638ac69e9: r8 name2
  $ hg outgoing $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  4 e71dbbc70e03: r4 name1
  $ hg pull $remote
  pulling from http://localhost:$HGPORT/
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 2 changes to 2 files
  (run 'hg update' to get a working copy)
  $ hg push $remote --new-branch
  pushing to http://localhost:$HGPORT/
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 1 changesets with 2 changes to 2 files
  $ hg incoming $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ hg outgoing $remote
  comparing with http://localhost:$HGPORT/
  searching for changes
  no changes found
  [1]
  $ cd ..
  $ tstop show
  "GET /?cmd=capabilities HTTP/1.1" 200 -
  "GET /?cmd=heads HTTP/1.1" 200 -
  "GET /?cmd=branches HTTP/1.1" 200 - x-hgarg-1:nodes=d8f638ac69e9ae8dea4f09f11d696546a912d961
  "GET /?cmd=between HTTP/1.1" 200 - x-hgarg-1:pairs=d8f638ac69e9ae8dea4f09f11d696546a912d961-d57206cc072a18317c1e381fb60aa31bd3401785
  "GET /?cmd=changegroupsubset HTTP/1.1" 200 - x-hgarg-1:bases=d8f638ac69e9ae8dea4f09f11d696546a912d961&heads=d8f638ac69e9ae8dea4f09f11d696546a912d961
  "GET /?cmd=listkeys HTTP/1.1" 200 - x-hgarg-1:namespace=phases
  "GET /?cmd=capabilities HTTP/1.1" 200 -
  "GET /?cmd=heads HTTP/1.1" 200 -
  "GET /?cmd=branches HTTP/1.1" 200 - x-hgarg-1:nodes=d8f638ac69e9ae8dea4f09f11d696546a912d961
  "GET /?cmd=between HTTP/1.1" 200 - x-hgarg-1:pairs=d8f638ac69e9ae8dea4f09f11d696546a912d961-d57206cc072a18317c1e381fb60aa31bd3401785
  "GET /?cmd=capabilities HTTP/1.1" 200 -
  "GET /?cmd=listkeys HTTP/1.1" 200 - x-hgarg-1:namespace=bookmarks
  "GET /?cmd=heads HTTP/1.1" 200 -
  "GET /?cmd=branches HTTP/1.1" 200 - x-hgarg-1:nodes=d8f638ac69e9ae8dea4f09f11d696546a912d961
  "GET /?cmd=between HTTP/1.1" 200 - x-hgarg-1:pairs=d8f638ac69e9ae8dea4f09f11d696546a912d961-d57206cc072a18317c1e381fb60aa31bd3401785
  "GET /?cmd=changegroupsubset HTTP/1.1" 200 - x-hgarg-1:bases=d8f638ac69e9ae8dea4f09f11d696546a912d961&heads=d8f638ac69e9ae8dea4f09f11d696546a912d961
  "GET /?cmd=listkeys HTTP/1.1" 200 - x-hgarg-1:namespace=phases
  "GET /?cmd=capabilities HTTP/1.1" 200 -
  "GET /?cmd=heads HTTP/1.1" 200 -
  "GET /?cmd=listkeys HTTP/1.1" 200 - x-hgarg-1:namespace=phases
  "GET /?cmd=listkeys HTTP/1.1" 200 - x-hgarg-1:namespace=bookmarks
  "GET /?cmd=branchmap HTTP/1.1" 200 -
  "GET /?cmd=branchmap HTTP/1.1" 200 -
  "GET /?cmd=listkeys HTTP/1.1" 200 - x-hgarg-1:namespace=bookmarks
  "POST /?cmd=unbundle HTTP/1.1" 200 - x-hgarg-1:heads=686173686564+1827a5bb63e602382eb89dd58f2ac9f3b007ad91* (glob)
  "GET /?cmd=listkeys HTTP/1.1" 200 - x-hgarg-1:namespace=phases
  "GET /?cmd=capabilities HTTP/1.1" 200 -
  "GET /?cmd=heads HTTP/1.1" 200 -
  "GET /?cmd=capabilities HTTP/1.1" 200 -
  "GET /?cmd=heads HTTP/1.1" 200 -