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.
# Here we create a simple DAG which has just enough of the required
# topology to test all the bisection status labels:
#
# 13--14
# /
# 0--1--2--3---------9--10--11--12
# \ /
# 4--5--6--7--8
$ hg init
$ echo '0' >a
$ hg add a
$ hg ci -u test -d '0 0' -m '0'
$ echo '1' >a
$ hg ci -u test -d '1 0' -m '1'
branch 2-3
$ echo '2' >b
$ hg add b
$ hg ci -u test -d '2 0' -m '2'
$ echo '3' >b
$ hg ci -u test -d '3 0' -m '3'
branch 4-8
$ hg up -r 1
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo '4' >c
$ hg add c
$ hg ci -u test -d '4 0' -m '4'
created new head
$ echo '5' >c
$ hg ci -u test -d '5 0' -m '5'
$ echo '6' >c
$ hg ci -u test -d '6 0' -m '6'
$ echo '7' >c
$ hg ci -u test -d '7 0' -m '7'
$ echo '8' >c
$ hg ci -u test -d '8 0' -m '8'
merge
$ hg merge -r 3
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -u test -d '9 0' -m '9=8+3'
$ echo '10' >a
$ hg ci -u test -d '10 0' -m '10'
$ echo '11' >a
$ hg ci -u test -d '11 0' -m '11'
$ echo '12' >a
$ hg ci -u test -d '12 0' -m '12'
unrelated branch
$ hg up -r 3
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo '13' >d
$ hg add d
$ hg ci -u test -d '13 0' -m '13'
created new head
$ echo '14' >d
$ hg ci -u test -d '14 0' -m '14'
mark changesets
$ hg bisect --reset
$ hg bisect --good 4
$ hg bisect --good 6
$ hg bisect --bad 12
Testing changeset 9:2197c557e14c (6 changesets remaining, ~2 tests)
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg bisect --bad 10
Testing changeset 8:e74a86251f58 (4 changesets remaining, ~2 tests)
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg bisect --skip 7
Testing changeset 8:e74a86251f58 (4 changesets remaining, ~2 tests)
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
test template
$ hg log --template '{rev}:{node|short} {bisect}\n'
14:cbf2f3105bbf
13:e07efca37c43
12:98c6b56349c0 bad
11:03f491376e63 bad (implicit)
10:c012b15e2409 bad
9:2197c557e14c untested
8:e74a86251f58 untested
7:a5f87041c899 skipped
6:7d997bedcd8d good
5:2dd1875f1028 good (implicit)
4:2a1daef14cd4 good
3:8417d459b90c ignored
2:e1355ee1f23e ignored
1:ce7c85e06a9f good (implicit)
0:b4e73ffab476 good (implicit)
$ hg log --template '{bisect|shortbisect} {rev}:{node|short}\n'
14:cbf2f3105bbf
13:e07efca37c43
B 12:98c6b56349c0
B 11:03f491376e63
B 10:c012b15e2409
U 9:2197c557e14c
U 8:e74a86251f58
S 7:a5f87041c899
G 6:7d997bedcd8d
G 5:2dd1875f1028
G 4:2a1daef14cd4
I 3:8417d459b90c
I 2:e1355ee1f23e
G 1:ce7c85e06a9f
G 0:b4e73ffab476
test style
$ hg log --style bisect
changeset: 14:cbf2f3105bbf
bisect:
tag: tip
user: test
date: Thu Jan 01 00:00:14 1970 +0000
summary: 14
changeset: 13:e07efca37c43
bisect:
parent: 3:8417d459b90c
user: test
date: Thu Jan 01 00:00:13 1970 +0000
summary: 13
changeset: 12:98c6b56349c0
bisect: bad
user: test
date: Thu Jan 01 00:00:12 1970 +0000
summary: 12
changeset: 11:03f491376e63
bisect: bad (implicit)
user: test
date: Thu Jan 01 00:00:11 1970 +0000
summary: 11
changeset: 10:c012b15e2409
bisect: bad
user: test
date: Thu Jan 01 00:00:10 1970 +0000
summary: 10
changeset: 9:2197c557e14c
bisect: untested
parent: 8:e74a86251f58
parent: 3:8417d459b90c
user: test
date: Thu Jan 01 00:00:09 1970 +0000
summary: 9=8+3
changeset: 8:e74a86251f58
bisect: untested
user: test
date: Thu Jan 01 00:00:08 1970 +0000
summary: 8
changeset: 7:a5f87041c899
bisect: skipped
user: test
date: Thu Jan 01 00:00:07 1970 +0000
summary: 7
changeset: 6:7d997bedcd8d
bisect: good
user: test
date: Thu Jan 01 00:00:06 1970 +0000
summary: 6
changeset: 5:2dd1875f1028
bisect: good (implicit)
user: test
date: Thu Jan 01 00:00:05 1970 +0000
summary: 5
changeset: 4:2a1daef14cd4
bisect: good
parent: 1:ce7c85e06a9f
user: test
date: Thu Jan 01 00:00:04 1970 +0000
summary: 4
changeset: 3:8417d459b90c
bisect: ignored
user: test
date: Thu Jan 01 00:00:03 1970 +0000
summary: 3
changeset: 2:e1355ee1f23e
bisect: ignored
user: test
date: Thu Jan 01 00:00:02 1970 +0000
summary: 2
changeset: 1:ce7c85e06a9f
bisect: good (implicit)
user: test
date: Thu Jan 01 00:00:01 1970 +0000
summary: 1
changeset: 0:b4e73ffab476
bisect: good (implicit)
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 0
$ hg log --quiet --style bisect
14:cbf2f3105bbf
13:e07efca37c43
B 12:98c6b56349c0
B 11:03f491376e63
B 10:c012b15e2409
U 9:2197c557e14c
U 8:e74a86251f58
S 7:a5f87041c899
G 6:7d997bedcd8d
G 5:2dd1875f1028
G 4:2a1daef14cd4
I 3:8417d459b90c
I 2:e1355ee1f23e
G 1:ce7c85e06a9f
G 0:b4e73ffab476
$ hg --config extensions.color= --color=debug log --quiet --style bisect
[log.bisect| ] 14:cbf2f3105bbf
[log.bisect| ] 13:e07efca37c43
[log.bisect bisect.bad|B] 12:98c6b56349c0
[log.bisect bisect.bad|B] 11:03f491376e63
[log.bisect bisect.bad|B] 10:c012b15e2409
[log.bisect bisect.untested|U] 9:2197c557e14c
[log.bisect bisect.untested|U] 8:e74a86251f58
[log.bisect bisect.skipped|S] 7:a5f87041c899
[log.bisect bisect.good|G] 6:7d997bedcd8d
[log.bisect bisect.good|G] 5:2dd1875f1028
[log.bisect bisect.good|G] 4:2a1daef14cd4
[log.bisect bisect.ignored|I] 3:8417d459b90c
[log.bisect bisect.ignored|I] 2:e1355ee1f23e
[log.bisect bisect.good|G] 1:ce7c85e06a9f
[log.bisect bisect.good|G] 0:b4e73ffab476