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
$ hg init
$ cat << EOF > a
> Small Mathematical Series.
> One
> Two
> Three
> Four
> Five
> Hop we are done.
> EOF
$ hg add a
$ hg commit -m ancestor
$ cat << EOF > a
> Small Mathematical Series.
> 1
> 2
> 3
> 4
> 5
> Hop we are done.
> EOF
$ hg commit -m branch1
$ hg co 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cat << EOF > a
> Small Mathematical Series.
> 1
> 2
> 3
> 6
> 8
> Hop we are done.
> EOF
$ hg commit -m branch2
created new head
$ hg merge 1
merging a
warning: conflicts while merging a! (edit, then use 'hg resolve --mark')
0 files updated, 0 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
[1]
$ hg id
618808747361+c0c68e4fe667+ tip
$ echo "[commands]" >> $HGRCPATH
$ echo "status.verbose=true" >> $HGRCPATH
$ hg status
M a
? a.orig
# The repository is in an unfinished *merge* state.
# Unresolved merge conflicts:
#
# a
#
# To mark files as resolved: hg resolve --mark FILE
# To continue: hg commit
# To abort: hg update --clean . (warning: this will discard uncommitted changes)
$ cat a
Small Mathematical Series.
1
2
3
<<<<<<< working copy: 618808747361 - test: branch2
6
8
=======
4
5
>>>>>>> merge rev: c0c68e4fe667 - test: branch1
Hop we are done.
$ hg status --config commands.status.verbose=0
M a
? a.orig
Verify custom conflict markers
$ hg up -q --clean .
$ cat <<EOF >> .hg/hgrc
> [ui]
> mergemarkertemplate = '{author} {rev}'
> EOF
$ hg merge 1
merging a
warning: conflicts while merging a! (edit, then use 'hg resolve --mark')
0 files updated, 0 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
[1]
$ cat a
Small Mathematical Series.
1
2
3
<<<<<<< working copy: test 2
6
8
=======
4
5
>>>>>>> merge rev: test 1
Hop we are done.
Verify line splitting of custom conflict marker which causes multiple lines
$ hg up -q --clean .
$ cat >> .hg/hgrc <<EOF
> [ui]
> mergemarkertemplate={author} {rev}\nfoo\nbar\nbaz
> EOF
$ hg -q merge 1
warning: conflicts while merging a! (edit, then use 'hg resolve --mark')
[1]
$ cat a
Small Mathematical Series.
1
2
3
<<<<<<< working copy: test 2
6
8
=======
4
5
>>>>>>> merge rev: test 1
Hop we are done.
Verify line trimming of custom conflict marker using multi-byte characters
$ hg up -q --clean .
$ $PYTHON <<EOF
> fp = open('logfile', 'w')
> fp.write('12345678901234567890123456789012345678901234567890' +
> '1234567890') # there are 5 more columns for 80 columns
>
> # 2 x 4 = 8 columns, but 3 x 4 = 12 bytes
> fp.write(u'\u3042\u3044\u3046\u3048'.encode('utf-8'))
>
> fp.close()
> EOF
$ hg add logfile
$ hg --encoding utf-8 commit --logfile logfile
$ cat >> .hg/hgrc <<EOF
> [ui]
> mergemarkertemplate={desc|firstline}
> EOF
$ hg -q --encoding utf-8 merge 1
warning: conflicts while merging a! (edit, then use 'hg resolve --mark')
[1]
$ cat a
Small Mathematical Series.
1
2
3
<<<<<<< working copy: 1234567890123456789012345678901234567890123456789012345...
6
8
=======
4
5
>>>>>>> merge rev: branch1
Hop we are done.
Verify basic conflict markers
$ hg up -q --clean 2
$ printf "\n[ui]\nmergemarkers=basic\n" >> .hg/hgrc
$ hg merge 1
merging a
warning: conflicts while merging a! (edit, then use 'hg resolve --mark')
0 files updated, 0 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
[1]
$ cat a
Small Mathematical Series.
1
2
3
<<<<<<< working copy
6
8
=======
4
5
>>>>>>> merge rev
Hop we are done.
internal:merge3
$ hg up -q --clean .
$ hg merge 1 --tool internal:merge3
merging a
warning: conflicts while merging a! (edit, then use 'hg resolve --mark')
0 files updated, 0 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
[1]
$ cat a
Small Mathematical Series.
<<<<<<< working copy
1
2
3
6
8
||||||| base
One
Two
Three
Four
Five
=======
1
2
3
4
5
>>>>>>> merge rev
Hop we are done.
Add some unconflicting changes on each head, to make sure we really
are merging, unlike :local and :other
$ hg up -C
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
updated to "e0693e20f496: 123456789012345678901234567890123456789012345678901234567890????"
1 other heads for branch "default"
$ printf "\n\nEnd of file\n" >> a
$ hg ci -m "Add some stuff at the end"
$ hg up -r 1
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ printf "Start of file\n\n\n" > tmp
$ cat a >> tmp
$ mv tmp a
$ hg ci -m "Add some stuff at the beginning"
Now test :merge-other and :merge-local
$ hg merge
merging a
warning: conflicts while merging a! (edit, then use 'hg resolve --mark')
1 files updated, 0 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
[1]
$ hg resolve --tool :merge-other a
merging a
(no more unresolved files)
$ cat a
Start of file
Small Mathematical Series.
1
2
3
6
8
Hop we are done.
End of file
$ hg up -C
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
updated to "18b51d585961: Add some stuff at the beginning"
1 other heads for branch "default"
$ hg merge --tool :merge-local
merging a
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat a
Start of file
Small Mathematical Series.
1
2
3
4
5
Hop we are done.
End of file