bundle2: increase payload part chunk size to 32kb
Bundle2 payload parts are framed chunks. Esentially, we obtain
data in equal size chunks of size `preferedchunksize` and emit those
to a generator. That generator is fed into a compressor (which can
be the no-op compressor, which just re-emits the generator). And
the output from the compressor likely goes to a file descriptor
or socket.
What this means is that small chunk sizes create more Python objects
and Python function calls than larger chunk sizes. And as we know,
Python object and function call overhead in performance sensitive
code matters (at least with CPython).
This commit increases the bundle2 part payload chunk size from 4k
to 32k. Practically speaking, this means that the chunks we feed
into a compressor (implemented in C code) or feed directly into a
file handle or socket write() are larger. It's possible the chunks
might be larger than what the receiver can handle in one logical
operation. But at that point, we're in C code, which is much more
efficient at dealing with splitting up the chunk and making multiple
function calls than Python is.
A downside to larger chunks is that the receiver has to wait for that
much data to arrive (either raw or from a decompressor) before it
can process the chunk. But 32kb still feels like a small buffer to
have to wait for. And in many cases, the client will convert from
8 read(4096) to 1 read(32768). That's happening in Python land. So
we cut down on the number of Python objects and function calls,
making the client faster as well. I don't think there are any
significant concerns to increasing the payload chunk size to 32kb.
The impact of this change on performance significant. Using `curl`
to obtain a stream clone bundle2 payload from a server on localhost
serving the mozilla-unified repository:
before: 20.78 user; 7.71 system; 80.5 MB/s
after: 13.90 user; 3.51 system; 132 MB/s
legacy: 9.72 user; 8.16 system; 132 MB/s
bundle2 stream clone generation is still more resource intensive than
legacy stream clone (that's likely because of the use of a
util.chunkbuffer). But the throughput is the same. We might
be in territory we're this is effectively a benchmark of the
networking stack or Python's syscall throughput.
From the client perspective, `hg clone -U --stream`:
before: 33.50 user; 7.95 system; 53.3 MB/s
after: 22.82 user; 7.33 system; 72.7 MB/s
legacy: 29.96 user; 7.94 system; 58.0 MB/s
And for `hg clone --stream` with a working directory update of
~230k files:
after: 119.55 user; 26.47 system; 0:57.08 wall
legacy: 126.98 user; 26.94 system; 1:05.56 wall
So, it appears that bundle2's stream clone is now definitively faster
than legacy stream clone!
Differential Revision: https://phab.mercurial-scm.org/D1932
$ cat >> $HGRCPATH <<EOF
> [extensions]
> rebase=
>
> [phases]
> publish=False
>
> [alias]
> tglog = log -G --template "{rev}: {node|short} '{desc}' {branches}\n"
> EOF
$ hg init a
$ cd a
$ hg unbundle "$TESTDIR/bundles/rebase.hg"
adding changesets
adding manifests
adding file changes
added 8 changesets with 7 changes to 7 files (+2 heads)
new changesets cd010b8cd998:02de42196ebe
(run 'hg heads' to see heads, 'hg merge' to merge)
$ hg up tip
3 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo I > I
$ hg ci -AmI
adding I
$ hg tglog
@ 8: e7ec4e813ba6 'I'
|
o 7: 02de42196ebe 'H'
|
| o 6: eea13746799a 'G'
|/|
o | 5: 24b6387c8c8c 'F'
| |
| o 4: 9520eea781bc 'E'
|/
| o 3: 32af7686d403 'D'
| |
| o 2: 5fddd98957c8 'C'
| |
| o 1: 42ccdea3bb16 'B'
|/
o 0: cd010b8cd998 'A'
$ cd ..
Version with only two heads (to allow default destination to work)
$ hg clone -q -u . a a2heads -r 3 -r 8
These fail:
$ hg clone -q -u . a a0
$ cd a0
$ hg rebase -s 8 -d 7
nothing to rebase
[1]
$ hg rebase --continue --abort
abort: cannot use both abort and continue
[255]
$ hg rebase --continue --collapse
abort: cannot use collapse with continue or abort
[255]
$ hg rebase --continue --dest 4
abort: abort and continue do not allow specifying revisions
[255]
$ hg rebase --base 5 --source 4
abort: cannot specify both a source and a base
[255]
$ hg rebase --rev 5 --source 4
abort: cannot specify both a revision and a source
[255]
$ hg rebase --base 5 --rev 4
abort: cannot specify both a revision and a base
[255]
$ hg rebase --base 6
abort: branch 'default' has 3 heads - please rebase to an explicit rev
(run 'hg heads .' to see heads)
[255]
$ hg rebase --rev '1 & !1' --dest 8
empty "rev" revision set - nothing to rebase
[1]
$ hg rebase --source '1 & !1' --dest 8
empty "source" revision set - nothing to rebase
[1]
$ hg rebase --base '1 & !1' --dest 8
empty "base" revision set - can't compute rebase set
[1]
$ hg rebase --dest 8
nothing to rebase - working directory parent is also destination
[1]
$ hg rebase -b . --dest 8
nothing to rebase - e7ec4e813ba6 is both "base" and destination
[1]
$ hg up -q 7
$ hg rebase --dest 8 --traceback
nothing to rebase - working directory parent is already an ancestor of destination e7ec4e813ba6
[1]
$ hg rebase --dest 8 -b.
nothing to rebase - "base" 02de42196ebe is already an ancestor of destination e7ec4e813ba6
[1]
$ hg rebase --dest '1 & !1'
abort: empty revision set
[255]
These work:
Rebase with no arguments (from 3 onto 8):
$ cd ..
$ hg clone -q -u . a2heads a1
$ cd a1
$ hg up -q -C 3
$ hg rebase
rebasing 1:42ccdea3bb16 "B"
rebasing 2:5fddd98957c8 "C"
rebasing 3:32af7686d403 "D"
saved backup bundle to $TESTTMP/a1/.hg/strip-backup/42ccdea3bb16-3cb021d3-rebase.hg
$ hg tglog
@ 6: ed65089c18f8 'D'
|
o 5: 7621bf1a2f17 'C'
|
o 4: 9430a62369c6 'B'
|
o 3: e7ec4e813ba6 'I'
|
o 2: 02de42196ebe 'H'
|
o 1: 24b6387c8c8c 'F'
|
o 0: cd010b8cd998 'A'
Try to rollback after a rebase (fail):
$ hg rollback
no rollback information available
[1]
$ cd ..
Rebase with base == '.' => same as no arguments (from 3 onto 8):
$ hg clone -q -u 3 a2heads a2
$ cd a2
$ hg rebase --base .
rebasing 1:42ccdea3bb16 "B"
rebasing 2:5fddd98957c8 "C"
rebasing 3:32af7686d403 "D"
saved backup bundle to $TESTTMP/a2/.hg/strip-backup/42ccdea3bb16-3cb021d3-rebase.hg
$ hg tglog
@ 6: ed65089c18f8 'D'
|
o 5: 7621bf1a2f17 'C'
|
o 4: 9430a62369c6 'B'
|
o 3: e7ec4e813ba6 'I'
|
o 2: 02de42196ebe 'H'
|
o 1: 24b6387c8c8c 'F'
|
o 0: cd010b8cd998 'A'
$ cd ..
Rebase with dest == branch(.) => same as no arguments (from 3 onto 8):
$ hg clone -q -u 3 a a3
$ cd a3
$ hg rebase --dest 'branch(.)'
rebasing 1:42ccdea3bb16 "B"
rebasing 2:5fddd98957c8 "C"
rebasing 3:32af7686d403 "D"
saved backup bundle to $TESTTMP/a3/.hg/strip-backup/42ccdea3bb16-3cb021d3-rebase.hg
$ hg tglog
@ 8: ed65089c18f8 'D'
|
o 7: 7621bf1a2f17 'C'
|
o 6: 9430a62369c6 'B'
|
o 5: e7ec4e813ba6 'I'
|
o 4: 02de42196ebe 'H'
|
| o 3: eea13746799a 'G'
|/|
o | 2: 24b6387c8c8c 'F'
| |
| o 1: 9520eea781bc 'E'
|/
o 0: cd010b8cd998 'A'
$ cd ..
Specify only source (from 2 onto 8):
$ hg clone -q -u . a2heads a4
$ cd a4
$ hg rebase --source 'desc("C")'
rebasing 2:5fddd98957c8 "C"
rebasing 3:32af7686d403 "D"
saved backup bundle to $TESTTMP/a4/.hg/strip-backup/5fddd98957c8-f9244fa1-rebase.hg
$ hg tglog
o 6: 7726e9fd58f7 'D'
|
o 5: 72c8333623d0 'C'
|
@ 4: e7ec4e813ba6 'I'
|
o 3: 02de42196ebe 'H'
|
o 2: 24b6387c8c8c 'F'
|
| o 1: 42ccdea3bb16 'B'
|/
o 0: cd010b8cd998 'A'
$ cd ..
Specify only dest (from 3 onto 6):
$ hg clone -q -u 3 a a5
$ cd a5
$ hg rebase --dest 6
rebasing 1:42ccdea3bb16 "B"
rebasing 2:5fddd98957c8 "C"
rebasing 3:32af7686d403 "D"
saved backup bundle to $TESTTMP/a5/.hg/strip-backup/42ccdea3bb16-3cb021d3-rebase.hg
$ hg tglog
@ 8: 8eeb3c33ad33 'D'
|
o 7: 2327fea05063 'C'
|
o 6: e4e5be0395b2 'B'
|
| o 5: e7ec4e813ba6 'I'
| |
| o 4: 02de42196ebe 'H'
| |
o | 3: eea13746799a 'G'
|\|
| o 2: 24b6387c8c8c 'F'
| |
o | 1: 9520eea781bc 'E'
|/
o 0: cd010b8cd998 'A'
$ cd ..
Specify only base (from 1 onto 8):
$ hg clone -q -u . a2heads a6
$ cd a6
$ hg rebase --base 'desc("D")'
rebasing 1:42ccdea3bb16 "B"
rebasing 2:5fddd98957c8 "C"
rebasing 3:32af7686d403 "D"
saved backup bundle to $TESTTMP/a6/.hg/strip-backup/42ccdea3bb16-3cb021d3-rebase.hg
$ hg tglog
o 6: ed65089c18f8 'D'
|
o 5: 7621bf1a2f17 'C'
|
o 4: 9430a62369c6 'B'
|
@ 3: e7ec4e813ba6 'I'
|
o 2: 02de42196ebe 'H'
|
o 1: 24b6387c8c8c 'F'
|
o 0: cd010b8cd998 'A'
$ cd ..
Specify source and dest (from 2 onto 7):
$ hg clone -q -u . a a7
$ cd a7
$ hg rebase --source 2 --dest 7
rebasing 2:5fddd98957c8 "C"
rebasing 3:32af7686d403 "D"
saved backup bundle to $TESTTMP/a7/.hg/strip-backup/5fddd98957c8-f9244fa1-rebase.hg
$ hg tglog
o 8: 668acadedd30 'D'
|
o 7: 09eb682ba906 'C'
|
| @ 6: e7ec4e813ba6 'I'
|/
o 5: 02de42196ebe 'H'
|
| o 4: eea13746799a 'G'
|/|
o | 3: 24b6387c8c8c 'F'
| |
| o 2: 9520eea781bc 'E'
|/
| o 1: 42ccdea3bb16 'B'
|/
o 0: cd010b8cd998 'A'
$ cd ..
Specify base and dest (from 1 onto 7):
$ hg clone -q -u . a a8
$ cd a8
$ hg rebase --base 3 --dest 7
rebasing 1:42ccdea3bb16 "B"
rebasing 2:5fddd98957c8 "C"
rebasing 3:32af7686d403 "D"
saved backup bundle to $TESTTMP/a8/.hg/strip-backup/42ccdea3bb16-3cb021d3-rebase.hg
$ hg tglog
o 8: 287cc92ba5a4 'D'
|
o 7: 6824f610a250 'C'
|
o 6: 7c6027df6a99 'B'
|
| @ 5: e7ec4e813ba6 'I'
|/
o 4: 02de42196ebe 'H'
|
| o 3: eea13746799a 'G'
|/|
o | 2: 24b6387c8c8c 'F'
| |
| o 1: 9520eea781bc 'E'
|/
o 0: cd010b8cd998 'A'
$ cd ..
Specify only revs (from 2 onto 8)
$ hg clone -q -u . a2heads a9
$ cd a9
$ hg rebase --rev 'desc("C")::'
rebasing 2:5fddd98957c8 "C"
rebasing 3:32af7686d403 "D"
saved backup bundle to $TESTTMP/a9/.hg/strip-backup/5fddd98957c8-f9244fa1-rebase.hg
$ hg tglog
o 6: 7726e9fd58f7 'D'
|
o 5: 72c8333623d0 'C'
|
@ 4: e7ec4e813ba6 'I'
|
o 3: 02de42196ebe 'H'
|
o 2: 24b6387c8c8c 'F'
|
| o 1: 42ccdea3bb16 'B'
|/
o 0: cd010b8cd998 'A'
$ cd ..
Rebasing both a single revision and a merge in one command
$ hg clone -q -u . a aX
$ cd aX
$ hg rebase -r 3 -r 6 --dest 8
rebasing 3:32af7686d403 "D"
rebasing 6:eea13746799a "G"
saved backup bundle to $TESTTMP/aX/.hg/strip-backup/eea13746799a-ad273fd6-rebase.hg
$ cd ..
Test --tool parameter:
$ hg init b
$ cd b
$ echo c1 > c1
$ hg ci -Am c1
adding c1
$ echo c2 > c2
$ hg ci -Am c2
adding c2
$ hg up -q 0
$ echo c2b > c2
$ hg ci -Am c2b
adding c2
created new head
$ cd ..
$ hg clone -q -u . b b1
$ cd b1
$ hg rebase -s 2 -d 1 --tool internal:local
rebasing 2:e4e3f3546619 "c2b" (tip)
note: rebase of 2:e4e3f3546619 created no changes to commit
saved backup bundle to $TESTTMP/b1/.hg/strip-backup/e4e3f3546619-b0841178-rebase.hg
$ hg cat c2
c2
$ cd ..
$ hg clone -q -u . b b2
$ cd b2
$ hg rebase -s 2 -d 1 --tool internal:other
rebasing 2:e4e3f3546619 "c2b" (tip)
saved backup bundle to $TESTTMP/b2/.hg/strip-backup/e4e3f3546619-b0841178-rebase.hg
$ hg cat c2
c2b
$ cd ..
$ hg clone -q -u . b b3
$ cd b3
$ hg rebase -s 2 -d 1 --tool internal:fail
rebasing 2:e4e3f3546619 "c2b" (tip)
unresolved conflicts (see hg resolve, then hg rebase --continue)
[1]
$ hg summary
parent: 1:56daeba07f4b
c2
parent: 2:e4e3f3546619 tip
c2b
branch: default
commit: 1 modified, 1 unresolved (merge)
update: (current)
phases: 3 draft
rebase: 0 rebased, 1 remaining (rebase --continue)
$ hg resolve -l
U c2
$ hg resolve -m c2
(no more unresolved files)
continue: hg rebase --continue
$ hg graft --continue
abort: no graft in progress
(continue: hg rebase --continue)
[255]
$ hg rebase -c --tool internal:fail
rebasing 2:e4e3f3546619 "c2b" (tip)
note: rebase of 2:e4e3f3546619 created no changes to commit
saved backup bundle to $TESTTMP/b3/.hg/strip-backup/e4e3f3546619-b0841178-rebase.hg
$ hg rebase -i
abort: interactive history editing is supported by the 'histedit' extension (see "hg --config extensions.histedit= help -e histedit")
[255]
$ hg rebase --interactive
abort: interactive history editing is supported by the 'histedit' extension (see "hg --config extensions.histedit= help -e histedit")
[255]
$ cd ..
No common ancestor
$ hg init separaterepo
$ cd separaterepo
$ touch a
$ hg commit -Aqm a
$ hg up -q null
$ touch b
$ hg commit -Aqm b
$ hg rebase -d 0
nothing to rebase from d7486e00c6f1 to 3903775176ed
[1]
$ cd ..