largefiles: optimize update speed by only updating changed largefiles
Historically, during 'hg update', every largefile in the working copy was
hashed (which is a very expensive operation on big files) and any
largefiles that did not have a hash that matched their standin were
updated.
This patch optimizes 'hg update' by keeping track of what standins have
changed between the old and new revisions, and only updating the largefiles
that have changed. This saves a lot of time by avoiding the unecessary
calculation of a list of sha1 hashes for big files.
With this patch, the time 'hg update' takes to complete is a function of
how many largefiles need to be updated and what their size is.
Performance tests on a repository with about 80 largefiles ranging from
a few MB to about 97 MB are shown below. The tests show how long it takes
to run 'hg update' with no changes actually being updated.
Mercurial 2.1 release:
$ time hg update
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
getting changed largefiles
0 largefiles updated, 0 removed
real 0m10.045s
user 0m9.367s
sys 0m0.674s
With this patch:
$ time hg update
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
real 0m0.965s
user 0m0.845s
sys 0m0.115s
The same repsoitory, without the largefiles extension enabled:
$ time hg update
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
real 0m0.799s
user 0m0.684s
sys 0m0.111s
So before the patch, 'hg update' with no changes was approximately 9.25s
slower with largefiles enabled. With this patch, it is approximately 0.165s
slower.
$ "$TESTDIR/hghave" tla symlink || exit 80
$ tla my-id "mercurial <mercurial@selenic.com>"
$ echo "[extensions]" >> $HGRCPATH
$ echo "convert=" >> $HGRCPATH
$ echo 'graphlog =' >> $HGRCPATH
create tla archive
$ tla make-archive tla@mercurial--convert `pwd`/hg-test-convert-tla
initialize tla repo
$ mkdir tla-repo
$ cd tla-repo/
$ tla init-tree tla@mercurial--convert/tla--test--0
$ tla import
* creating version tla@mercurial--convert/tla--test--0
* imported tla@mercurial--convert/tla--test--0
create initial files
$ echo 'this is a file' > a
$ tla add a
$ mkdir src
$ tla add src
$ cd src
$ dd count=1 if=/dev/zero of=b > /dev/null 2> /dev/null
$ tla add b
$ tla commit -s "added a file, src and src/b (binary)"
A/ .arch-ids
A/ src
A/ src/.arch-ids
A .arch-ids/a.id
A a
A src/.arch-ids/=id
A src/.arch-ids/b.id
A src/b
* update pristine tree (tla@mercurial--convert/tla--test--0--base-0 => tla--test--0--patch-1)
* committed tla@mercurial--convert/tla--test--0--patch-1
create link file and modify a
$ ln -s ../a a-link
$ tla add a-link
$ echo 'this a modification to a' >> ../a
$ tla commit -s "added link to a and modify a"
A src/.arch-ids/a-link.id
A src/a-link
M a
* update pristine tree (tla@mercurial--convert/tla--test--0--patch-1 => tla--test--0--patch-2)
* committed tla@mercurial--convert/tla--test--0--patch-2
create second link and modify b
$ ln -s ../a a-link-2
$ tla add a-link-2
$ dd count=1 seek=1 if=/dev/zero of=b > /dev/null 2> /dev/null
$ tla commit -s "added second link and modify b"
A src/.arch-ids/a-link-2.id
A src/a-link-2
Mb src/b
* update pristine tree (tla@mercurial--convert/tla--test--0--patch-2 => tla--test--0--patch-3)
* committed tla@mercurial--convert/tla--test--0--patch-3
b file to link and a-link-2 to regular file
$ rm -f a-link-2
$ echo 'this is now a regular file' > a-link-2
$ ln -sf ../a b
$ tla commit -s "file to link and link to file test"
fl src/b
lf src/a-link-2
* update pristine tree (tla@mercurial--convert/tla--test--0--patch-3 => tla--test--0--patch-4)
* committed tla@mercurial--convert/tla--test--0--patch-4
move a-link-2 file and src directory
$ cd ..
$ tla mv src/a-link-2 c
$ tla mv src test
$ tla commit -s "move and rename a-link-2 file and src directory"
D/ src/.arch-ids
A/ test/.arch-ids
/> src test
=> src/.arch-ids/a-link-2.id .arch-ids/c.id
=> src/a-link-2 c
=> src/.arch-ids/=id test/.arch-ids/=id
=> src/.arch-ids/a-link.id test/.arch-ids/a-link.id
=> src/.arch-ids/b.id test/.arch-ids/b.id
* update pristine tree (tla@mercurial--convert/tla--test--0--patch-4 => tla--test--0--patch-5)
* committed tla@mercurial--convert/tla--test--0--patch-5
$ cd ..
converting tla repo to Mercurial
$ hg convert tla-repo tla-repo-hg
initializing destination tla-repo-hg repository
analyzing tree version tla@mercurial--convert/tla--test--0...
scanning source...
sorting...
converting...
5 initial import
4 added a file, src and src/b (binary)
3 added link to a and modify a
2 added second link and modify b
1 file to link and link to file test
0 move and rename a-link-2 file and src directory
$ tla register-archive -d tla@mercurial--convert
$ glog()
> {
> hg glog --template '{rev} "{desc|firstline}" files: {files}\n' "$@"
> }
show graph log
$ glog -R tla-repo-hg
o 5 "move and rename a-link-2 file and src directory" files: c src/a-link src/a-link-2 src/b test/a-link test/b
|
o 4 "file to link and link to file test" files: src/a-link-2 src/b
|
o 3 "added second link and modify b" files: src/a-link-2 src/b
|
o 2 "added link to a and modify a" files: a src/a-link
|
o 1 "added a file, src and src/b (binary)" files: a src/b
|
o 0 "initial import" files:
$ hg up -q -R tla-repo-hg
$ hg -R tla-repo-hg manifest --debug
c4072c4b72e1cabace081888efa148ee80ca3cbb 644 a
0201ac32a3a8e86e303dff60366382a54b48a72e 644 c
c0067ba5ff0b7c9a3eb17270839d04614c435623 644 @ test/a-link
375f4263d86feacdea7e3c27100abd1560f2a973 644 @ test/b