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.
$ cat >> $HGRCPATH <<EOF
> [extensions]
> rebase=
> mq=
>
> [mq]
> plain=true
>
> [alias]
> tglog = log -G --template "{rev}: '{desc}' tags: {tags}\n"
> EOF
$ hg init a
$ cd a
$ hg qinit -c
$ echo c1 > f
$ hg add f
$ hg ci -m C1
$ echo r1 > f
$ hg ci -m R1
$ hg up -q 0
$ hg qnew f.patch -d '1 0'
$ echo mq1 > f
$ hg qref -m P0
$ hg qnew f2.patch
$ echo mq2 > f
$ hg qref -m P1 -d '2 0'
$ hg tglog
@ 3: 'P1' tags: f2.patch qtip tip
|
o 2: 'P0' tags: f.patch qbase
|
| o 1: 'R1' tags:
|/
o 0: 'C1' tags: qparent
Rebase - try to rebase on an applied mq patch:
$ hg rebase -s 1 -d 3
abort: cannot rebase onto an applied mq patch
[255]
Rebase - same thing, but mq patch is default dest:
$ hg up -q 1
$ hg rebase
abort: cannot rebase onto an applied mq patch
[255]
$ hg up -q qtip
Rebase - generate a conflict:
$ hg rebase -s 2 -d 1
rebasing 2:3504f44bffc0 "P0" (f.patch qbase)
merging f
warning: conflicts during merge.
merging f incomplete! (edit conflicts, then use 'hg resolve --mark')
unresolved conflicts (see hg resolve, then hg rebase --continue)
[1]
Fix the 1st conflict:
$ echo mq1r1 > f
$ hg resolve -m f
(no more unresolved files)
$ hg rebase -c
rebasing 2:3504f44bffc0 "P0" (f.patch qbase)
rebasing 3:929394423cd3 "P1" (f2.patch qtip tip)
merging f
warning: conflicts during merge.
merging f incomplete! (edit conflicts, then use 'hg resolve --mark')
unresolved conflicts (see hg resolve, then hg rebase --continue)
[1]
Fix the 2nd conflict:
$ echo mq1r1mq2 > f
$ hg resolve -m f
(no more unresolved files)
$ hg rebase -c
already rebased 2:3504f44bffc0 "P0" (f.patch qbase) as ebe9914c0d1c
rebasing 3:929394423cd3 "P1" (f2.patch qtip)
saved backup bundle to $TESTTMP/a/.hg/strip-backup/3504f44bffc0-30595b40-backup.hg (glob)
$ hg tglog
@ 3: 'P1' tags: f2.patch qtip tip
|
o 2: 'P0' tags: f.patch qbase
|
o 1: 'R1' tags: qparent
|
o 0: 'C1' tags:
$ hg up -q qbase
$ cat f
mq1r1
$ cat .hg/patches/f.patch
# HG changeset patch
# User test
# Date 1 0
# Thu Jan 01 00:00:01 1970 +0000
# Node ID ebe9914c0d1c3f60096e952fa4dbb3d377dea3ab
# Parent bac9ed9960d8992bcad75864a879fa76cadaf1b0
P0
diff -r bac9ed9960d8 -r ebe9914c0d1c f
--- a/f Thu Jan 01 00:00:00 1970 +0000
+++ b/f Thu Jan 01 00:00:01 1970 +0000
@@ -1,1 +1,1 @@
-r1
+mq1r1
Update to qtip:
$ hg up -q qtip
$ cat f
mq1r1mq2
$ cat .hg/patches/f2.patch
# HG changeset patch
# User test
# Date 2 0
# Thu Jan 01 00:00:02 1970 +0000
# Node ID 462012cf340c97d44d62377c985a423f6bb82f07
# Parent ebe9914c0d1c3f60096e952fa4dbb3d377dea3ab
P1
diff -r ebe9914c0d1c -r 462012cf340c f
--- a/f Thu Jan 01 00:00:01 1970 +0000
+++ b/f Thu Jan 01 00:00:02 1970 +0000
@@ -1,1 +1,1 @@
-mq1r1
+mq1r1mq2
Adding one git-style patch and one normal:
$ hg qpop -a
popping f2.patch
popping f.patch
patch queue now empty
$ rm -fr .hg/patches
$ hg qinit -c
$ hg up -q 0
$ hg qnew --git f_git.patch -d '3 0'
$ echo mq1 > p
$ hg add p
$ hg qref --git -m 'P0 (git)'
$ hg qnew f.patch -d '4 0'
$ echo mq2 > p
$ hg qref -m P1
$ hg qci -m 'save patch state'
$ hg qseries -s
f_git.patch: P0 (git)
f.patch: P1
$ hg -R .hg/patches manifest
.hgignore
f.patch
f_git.patch
series
$ cat .hg/patches/f_git.patch
Date: 3 0
P0 (git)
diff --git a/p b/p
new file mode 100644
--- /dev/null
+++ b/p
@@ -0,0 +1,1 @@
+mq1
$ cat .hg/patches/f.patch
Date: 4 0
P1
diff -r ???????????? p (glob)
--- a/p ??? ??? ?? ??:??:?? ???? ????? (glob)
+++ b/p ??? ??? ?? ??:??:?? ???? ????? (glob)
@@ -1,1 +1,1 @@
-mq1
+mq2
Rebase the applied mq patches:
$ hg rebase -s 2 -d 1
rebasing 2:0c587ffcb480 "P0 (git)" (f_git.patch qbase)
rebasing 3:c7f18665e4bc "P1" (f.patch qtip tip)
saved backup bundle to $TESTTMP/a/.hg/strip-backup/0c587ffcb480-0ea5695f-backup.hg (glob)
$ hg qci -m 'save patch state'
$ hg qseries -s
f_git.patch: P0 (git)
f.patch: P1
$ hg -R .hg/patches manifest
.hgignore
f.patch
f_git.patch
series
$ cat .hg/patches/f_git.patch
# HG changeset patch
# User test
# Date 3 0
# Thu Jan 01 00:00:03 1970 +0000
# Node ID 12d9f6a3bbe560dee50c7c454d434add7fb8e837
# Parent bac9ed9960d8992bcad75864a879fa76cadaf1b0
P0 (git)
diff --git a/p b/p
new file mode 100644
--- /dev/null
+++ b/p
@@ -0,0 +1,1 @@
+mq1
$ cat .hg/patches/f.patch
# HG changeset patch
# User test
# Date 4 0
# Thu Jan 01 00:00:04 1970 +0000
# Node ID c77a2661c64c60d82f63c4f7aefd95b3a948a557
# Parent 12d9f6a3bbe560dee50c7c454d434add7fb8e837
P1
diff -r 12d9f6a3bbe5 -r c77a2661c64c p
--- a/p Thu Jan 01 00:00:03 1970 +0000
+++ b/p Thu Jan 01 00:00:04 1970 +0000
@@ -1,1 +1,1 @@
-mq1
+mq2
$ cd ..
Rebase with guards
$ hg init foo
$ cd foo
$ echo a > a
$ hg ci -Am a
adding a
Create mq repo with guarded patches foo and bar and empty patch:
$ hg qinit
$ echo guarded > guarded
$ hg add guarded
$ hg qnew guarded
$ hg qnew empty-important -m 'important commit message' -d '1 0'
$ echo bar > bar
$ hg add bar
$ hg qnew bar -d '2 0'
$ echo foo > foo
$ hg add foo
$ hg qnew foo
$ hg qpop -a
popping foo
popping bar
popping empty-important
popping guarded
patch queue now empty
$ hg qguard guarded +guarded
$ hg qguard bar +baz
$ hg qguard foo +baz
$ hg qselect baz
number of unguarded, unapplied patches has changed from 1 to 3
$ hg qpush bar
applying empty-important
patch empty-important is empty
applying bar
now at: bar
$ hg qguard -l
guarded: +guarded
empty-important: unguarded
bar: +baz
foo: +baz
$ hg tglog
@ 2: 'imported patch bar' tags: bar qtip tip
|
o 1: 'important commit message' tags: empty-important qbase
|
o 0: 'a' tags: qparent
Create new head to rebase bar onto:
$ hg up -C 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo b > b
$ hg add b
$ hg ci -m b
created new head
$ hg up -C 2
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo a >> a
$ hg qref
$ hg tglog
@ 3: '[mq]: bar' tags: bar qtip tip
|
| o 2: 'b' tags:
| |
o | 1: 'important commit message' tags: empty-important qbase
|/
o 0: 'a' tags: qparent
Rebase bar (make sure series order is preserved and empty-important also is
removed from the series):
$ hg qseries
guarded
empty-important
bar
foo
$ [ -f .hg/patches/empty-important ]
$ hg -q rebase -d 2
note: rebase of 1:0aaf4c3af7eb created no changes to commit
$ hg qseries
guarded
bar
foo
$ [ -f .hg/patches/empty-important ]
[1]
$ hg qguard -l
guarded: +guarded
bar: +baz
foo: +baz
$ hg tglog
@ 2: '[mq]: bar' tags: bar qbase qtip tip
|
o 1: 'b' tags: qparent
|
o 0: 'a' tags:
$ cd ..