changegroup: compute seen files as changesets are added (
issue4750)
Before this patch, addchangegroup() would walk the changelog and compute
the set of seen files between applying changesets and applying
manifests. When cloning large repositories such as mozilla-central,
this consumed a non-trivial amount of time. On my MBP, this walk takes
~10s. On a dainty EC2 instance, this was measured to take ~125s! On the
latter machine, this delay was enough for the Mercurial server to
disconnect the client, thinking it had timed out, thus causing a clone
to abort.
This patch enables the changelog to compute the set of changed files as
new revisions are added. By doing so, we:
* avoid a potentially heavy computation between changelog and manifest
processing by spreading the computation across all changelog additions
* avoid extra reads from the changelog by operating on the data as it is
added
The downside of this is that the add revision callback does result in
extra I/O. Before, we would perform a flush (and subsequent read to
construct the full revision) when new delta chains were created. For
changelogs, this is typically every 2-4 revisions. Using the callback
guarantees there will be a flush after every added revision *and* an
open + read of the changelog to obtain the full revision in order to
read the added files. So, this increases the frequency of these
operations by the average chain length. In the future, the revlog
should be smart enough to know how to read revisions that haven't been
flushed yet, thus eliminating this extra I/O.
On my MBP, the total CPU times for an `hg unbundle` with a local
mozilla-central gzip bundle containing 251,934 changesets and 211,065
files did not have a statistically significant change with this patch,
holding steady around 360s. So, the increased revlog flushing did not
have an effect.
With this patch, there is no longer a visible pause between applying
changeset and manifest data. Before, it sure felt like Mercurial was
lethargic making this transition. Now, the transition is nearly
instantaneous, giving the impression that Mercurial is faster. Of course,
eliminating this pause means that the potential for network disconnect due
to channel inactivity during the changelog walk is eliminated as well.
And that is the impetus behind this change.
$ echo "[extensions]" >> $HGRCPATH
$ echo "largefiles =" >> $HGRCPATH
Create the repository outside $HOME since largefiles write to
$HOME/.cache/largefiles.
$ hg init test
$ cd test
$ echo "root" > root
$ hg add root
$ hg commit -m "Root commit" --config extensions.largefiles=!
Ensure that .hg/largefiles isn't created before largefiles are added
#if unix-permissions
$ chmod 555 .hg
#endif
$ hg status
#if unix-permissions
$ chmod 755 .hg
#endif
$ test -f .hg/largefiles
[1]
$ echo "large" > foo
$ hg add --large foo
$ hg commit -m "Add foo as a largefile"
$ hg update -r 0
getting changed largefiles
0 largefiles updated, 1 removed
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo "normal" > foo
$ hg add foo
$ hg commit -m "Add foo as normal file"
created new head
Normal file in the working copy, keeping the normal version:
$ echo "n" | hg merge --config ui.interactive=Yes
remote turned local normal file foo into a largefile
use (l)argefile or keep (n)ormal file? n
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg status
$ cat foo
normal
Normal file in the working copy, keeping the largefile version:
$ hg update -q -C
$ echo "l" | hg merge --config ui.interactive=Yes
remote turned local normal file foo into a largefile
use (l)argefile or keep (n)ormal file? l
getting changed largefiles
1 largefiles updated, 0 removed
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg status
M foo
$ hg diff --nodates
diff -r fa129ab6b5a7 .hglf/foo
--- /dev/null
+++ b/.hglf/foo
@@ -0,0 +1,1 @@
+7f7097b041ccf68cc5561e9600da4655d21c6d18
diff -r fa129ab6b5a7 foo
--- a/foo
+++ /dev/null
@@ -1,1 +0,0 @@
-normal
$ cat foo
large
Largefile in the working copy, keeping the normal version:
$ hg update -q -C -r 1
$ echo "n" | hg merge --config ui.interactive=Yes
remote turned local largefile foo into a normal file
keep (l)argefile or use (n)ormal file? n
getting changed largefiles
0 largefiles updated, 0 removed
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg status
M foo
$ hg diff --nodates
diff -r ff521236428a .hglf/foo
--- a/.hglf/foo
+++ /dev/null
@@ -1,1 +0,0 @@
-7f7097b041ccf68cc5561e9600da4655d21c6d18
diff -r ff521236428a foo
--- /dev/null
+++ b/foo
@@ -0,0 +1,1 @@
+normal
$ cat foo
normal
Largefile in the working copy, keeping the largefile version:
$ hg update -q -C -r 1
$ echo "l" | hg merge --config ui.interactive=Yes
remote turned local largefile foo into a normal file
keep (l)argefile or use (n)ormal file? l
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg status
$ cat foo
large
Whatever ... commit something so we can invoke merge when updating
$ hg commit -m '3: Merge'
Updating from largefile to normal - no reason to prompt
$ hg up -r 2
getting changed largefiles
0 largefiles updated, 0 removed
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ cat foo
normal
(the update above used to leave the working dir in a very weird state - clean it
$ hg up -qr null
$ hg up -qr 2
)
Updating from normal to largefile - no reason to prompt
$ hg up -r 3
getting changed largefiles
1 largefiles updated, 0 removed
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ cat foo
large
$ cd ..
Systematic testing of merges involving largefiles:
Ancestor: normal Parent: normal-id Parent: large result: large
Ancestor: normal Parent: normal2 Parent: large result: ?
Ancestor: large Parent: large-id Parent: normal result: normal
Ancestor: large Parent: large2 Parent: normal result: ?
All cases should try merging both ways.
Prepare test repo:
$ hg init merges
$ cd merges
prepare cases with "normal" ancestor:
$ hg up -qr null
$ echo normal > f
$ hg ci -Aqm "normal-ancestor"
$ hg tag -l "normal-ancestor"
$ touch f2
$ hg ci -Aqm "normal-id"
$ hg tag -l "normal-id"
$ echo normal2 > f
$ hg ci -m "normal2"
$ hg tag -l "normal2"
$ echo normal > f
$ hg ci -Aqm "normal-same"
$ hg tag -l "normal-same"
$ hg up -qr "normal-ancestor"
$ hg rm f
$ echo large > f
$ hg add --large f
$ hg ci -qm "large"
$ hg tag -l "large"
prepare cases with "large" ancestor:
$ hg up -qr null
$ echo large > f
$ hg add --large f
$ hg ci -qm "large-ancestor"
$ hg tag -l "large-ancestor"
$ touch f2
$ hg ci -Aqm "large-id"
$ hg tag -l "large-id"
$ echo large2 > f
$ hg ci -m "large2"
$ hg tag -l "large2"
$ echo large > f
$ hg ci -Aqm "large-same"
$ hg tag -l "large-same"
$ hg up -qr "large-ancestor"
$ hg rm f
$ echo normal > f
$ hg ci -qAm "normal"
$ hg tag -l "normal"
$ hg log -GT '{tags}'
@ normal tip
|
| o large-same
| |
| o large2
| |
| o large-id
|/
o large-ancestor
o large
|
| o normal-same
| |
| o normal2
| |
| o normal-id
|/
o normal-ancestor
Ancestor: normal Parent: normal-id Parent: large result: large
$ hg up -Cqr normal-id
$ hg merge -r large
getting changed largefiles
1 largefiles updated, 0 removed
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f
large
swap
$ hg up -Cqr large
$ hg merge -r normal-id
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f
large
Ancestor: normal Parent: normal-same Parent: large result: large
$ hg up -Cqr normal-same
$ hg merge -r large
getting changed largefiles
1 largefiles updated, 0 removed
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f
large
swap
$ hg up -Cqr large
$ hg merge -r normal-same
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f
large
Ancestor: normal Parent: normal2 Parent: large result: ?
(annoying extra prompt ... but it do not do any serious harm)
$ hg up -Cqr normal2
$ hg merge -r large
remote turned local normal file f into a largefile
use (l)argefile or keep (n)ormal file? l
getting changed largefiles
1 largefiles updated, 0 removed
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f
large
$ hg up -Cqr normal2
$ echo n | hg merge -r large --config ui.interactive=Yes
remote turned local normal file f into a largefile
use (l)argefile or keep (n)ormal file? n
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f
normal2
swap
$ hg up -Cqr large
$ hg merge -r normal2
remote turned local largefile f into a normal file
keep (l)argefile or use (n)ormal file? l
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f
large
$ hg up -Cqr large
$ echo n | hg merge -r normal2 --config ui.interactive=Yes
remote turned local largefile f into a normal file
keep (l)argefile or use (n)ormal file? n
getting changed largefiles
0 largefiles updated, 0 removed
2 files updated, 0 files merged, 1 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f
normal2
Ancestor: large Parent: large-id Parent: normal result: normal
$ hg up -Cqr large-id
$ hg merge -r normal
getting changed largefiles
0 largefiles updated, 0 removed
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f
normal
swap
$ hg up -Cqr normal
$ hg merge -r large-id
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f
normal
Ancestor: large Parent: large-same Parent: normal result: normal
$ hg up -Cqr large-same
$ hg merge -r normal
getting changed largefiles
0 largefiles updated, 0 removed
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f
normal
swap
$ hg up -Cqr normal
$ hg merge -r large-same
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f
normal
Ancestor: large Parent: large2 Parent: normal result: ?
(annoying extra prompt ... but it do not do any serious harm)
$ hg up -Cqr large2
$ hg merge -r normal
remote turned local largefile f into a normal file
keep (l)argefile or use (n)ormal file? l
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f
large2
$ hg up -Cqr large2
$ echo n | hg merge -r normal --config ui.interactive=Yes
remote turned local largefile f into a normal file
keep (l)argefile or use (n)ormal file? n
getting changed largefiles
0 largefiles updated, 0 removed
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f
normal
swap
$ hg up -Cqr normal
$ hg merge -r large2
remote turned local normal file f into a largefile
use (l)argefile or keep (n)ormal file? l
getting changed largefiles
1 largefiles updated, 0 removed
2 files updated, 0 files merged, 1 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f
large2
$ hg up -Cqr normal
$ echo n | hg merge -r large2 --config ui.interactive=Yes
remote turned local normal file f into a largefile
use (l)argefile or keep (n)ormal file? n
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat f
normal
$ cd ..