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.
$ hg init
$ echo "[merge]" >> .hg/hgrc
$ echo "followcopies = 1" >> .hg/hgrc
$ echo foo > a
$ echo foo > a2
$ hg add a a2
$ hg ci -m "start"
$ hg mv a b
$ hg mv a2 b2
$ hg ci -m "rename"
$ hg co 0
2 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ echo blahblah > a
$ echo blahblah > a2
$ hg mv a2 c2
$ hg ci -m "modify"
created new head
$ hg merge -y --debug
searching for copies back to rev 1
unmatched files in local:
c2
unmatched files in other:
b
b2
all copies found (* = to merge, ! = divergent):
c2 -> a2 !
b -> a *
b2 -> a2 !
checking for directory renames
a2: divergent renames -> dr
resolving manifests
overwrite: False, partial: False
ancestor: af1939970a1c, local: 044f8520aeeb+, remote: 85c198ef2f6c
a: remote moved to b -> m
b2: remote created -> g
preserving a for resolve of b
removing a
updating: a 1/3 files (33.33%)
picked tool 'internal:merge' for b (binary False symlink False)
merging a and b to b
my b@044f8520aeeb+ other b@85c198ef2f6c ancestor a@af1939970a1c
premerge successful
updating: a2 2/3 files (66.67%)
note: possible conflict - a2 was renamed multiple times to:
c2
b2
updating: b2 3/3 files (100.00%)
getting b2
1 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg status -AC
M b
a
M b2
R a
C c2
$ cat b
blahblah
$ hg ci -m "merge"
$ hg debugindex b
rev offset length base linkrev nodeid p1 p2
0 0 67 0 1 57eacc201a7f 000000000000 000000000000
1 67 72 1 3 4727ba907962 000000000000 57eacc201a7f
$ hg debugrename b
b renamed from a:dd03b83622e78778b403775d0d074b9ac7387a66
This used to trigger a "divergent renames" warning, despite no renames
$ hg cp b b3
$ hg cp b b4
$ hg ci -A -m 'copy b twice'
$ hg up eb92d88a9712
0 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ hg up
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg rm b3 b4
$ hg ci -m 'clean up a bit of our mess'
We'd rather not warn on divergent renames done in the same changeset (issue2113)
$ hg cp b b3
$ hg mv b b4
$ hg ci -A -m 'divergent renames in same changeset'
$ hg up c761c6948de0
1 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ hg up
note: possible conflict - b was renamed multiple times to:
b3
b4
2 files updated, 0 files merged, 1 files removed, 0 files unresolved
Check for issue2642
$ hg init t
$ cd t
$ echo c0 > f1
$ hg ci -Aqm0
$ hg up null -q
$ echo c1 > f1 # backport
$ hg ci -Aqm1
$ hg mv f1 f2
$ hg ci -qm2
$ hg up 0 -q
$ hg merge 1 -q --tool internal:local
$ hg ci -qm3
$ hg merge 2
merging f1 and f2 to f2
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f2
c0
Check for issue2089
$ hg init repo2089
$ cd repo2089
$ echo c0 > f1
$ hg ci -Aqm0
$ hg up null -q
$ echo c1 > f1
$ hg ci -Aqm1
$ hg up 0 -q
$ hg merge 1 -q --tool internal:local
$ echo c2 > f1
$ hg ci -qm2
$ hg up 1 -q
$ hg mv f1 f2
$ hg ci -Aqm3
$ hg up 2 -q
$ hg merge 3
merging f1 and f2 to f2
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f2
c2