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.
http://mercurial.selenic.com/bts/issue1306
Initialize remote repo with branches:
$ hg init remote
$ cd remote
$ echo a > a
$ hg ci -Ama
adding a
$ hg branch br
marked working directory as branch br
(branches are permanent and global, did you want a bookmark?)
$ hg ci -Amb
$ echo c > c
$ hg ci -Amc
adding c
$ hg log
changeset: 2:ae3d9c30ec50
branch: br
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: c
changeset: 1:3f7f930ca414
branch: br
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: b
changeset: 0:cb9a9f314b8b
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: a
$ cd ..
Try cloning -r branch:
$ hg clone -rbr remote local1
adding changesets
adding manifests
adding file changes
added 3 changesets with 2 changes to 2 files
updating to branch br
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg -R local1 parents
changeset: 2:ae3d9c30ec50
branch: br
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: c
Try cloning -rother clone#branch:
$ hg clone -r0 remote#br local2
adding changesets
adding manifests
adding file changes
added 3 changesets with 2 changes to 2 files
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg -R local2 parents
changeset: 0:cb9a9f314b8b
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: a
Try cloning -r1 clone#branch:
$ hg clone -r1 remote#br local3
adding changesets
adding manifests
adding file changes
added 3 changesets with 2 changes to 2 files
updating to branch br
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg -R local3 parents
changeset: 1:3f7f930ca414
branch: br
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: b