tests/test-bundle-type.t
| author |
Gregory Szorc <gregory.szorc@gmail.com> |
|
Fri, 11 Nov 2016 01:10:07 -0800 |
| changeset 30442 |
41a8106789ca |
| parent 29971 |
e65d33182fd4
|
| child 30758 |
76104a4899ad |
| permissions |
-rw-r--r-- |
util: implement zstd compression engine
Now that zstd is vendored and being built (in some configurations), we
can implement a compression engine for zstd!
The zstd engine is a little different from existing engines. Because
it may not always be present, we have to defer load the module in case
importing it fails. We facilitate this via a cached property that holds
a reference to the module or None. The "available" method is
implemented to reflect reality.
The zstd engine declares its ability to handle bundles using the
"zstd" human name and the "ZS" internal name. The latter was chosen
because internal names are 2 characters (by only convention I think)
and "ZS" seems reasonable.
The engine, like others, supports specifying the compression level.
However, there are no consumers of this API that yet pass in that
argument. I have plans to change that, so stay tuned.
Since all we need to do to support bundle generation with a new
compression engine is implement and register the compression engine,
bundle generation with zstd "just works!" Tests demonstrating this
have been added.
How does performance of zstd for bundle generation compare? On the
mozilla-unified repo, `hg bundle --all -t <engine>-v2` yields the
following on my i7-6700K on Linux:
engine CPU time bundle size vs orig size throughput
none 97.0s 4,054,405,584 100.0% 41.8 MB/s
bzip2 (l=9) 393.6s 975,343,098 24.0% 10.3 MB/s
gzip (l=6) 184.0s 1,140,533,074 28.1% 22.0 MB/s
zstd (l=1) 108.2s 1,119,434,718 27.6% 37.5 MB/s
zstd (l=2) 111.3s 1,078,328,002 26.6% 36.4 MB/s
zstd (l=3) 113.7s 1,011,823,727 25.0% 35.7 MB/s
zstd (l=4) 116.0s 1,008,965,888 24.9% 35.0 MB/s
zstd (l=5) 121.0s 977,203,148 24.1% 33.5 MB/s
zstd (l=6) 131.7s 927,360,198 22.9% 30.8 MB/s
zstd (l=7) 139.0s 912,808,505 22.5% 29.2 MB/s
zstd (l=12) 198.1s 854,527,714 21.1% 20.5 MB/s
zstd (l=18) 681.6s 789,750,690 19.5% 5.9 MB/s
On compression, zstd for bundle generation delivers:
* better compression than gzip with significantly less CPU utilization
* better than bzip2 compression ratios while still being significantly
faster than gzip
* ability to aggressively tune compression level to achieve
significantly smaller bundles
That last point is important. With clone bundles, a server can
pre-generate a bundle file, upload it to a static file server, and
redirect clients to transparently download it during clone. The server
could choose to produce a zstd bundle with the highest compression
settings possible. This would take a very long time - a magnitude
longer than a typical zstd bundle generation - but the result would
be hundreds of megabytes smaller! For the clone volume we do at
Mozilla, this could translate to petabytes of bandwidth savings
per year and faster clones (due to smaller transfer size).
I don't have detailed numbers to report on decompression. However,
zstd decompression is fast: >1 GB/s output throughput on this machine,
even through the Python bindings. And it can do that regardless of the
compression level of the input. By the time you have enough data to
worry about overhead of decompression, you have plenty of other things
to worry about performance wise.
zstd is wins all around. I can't wait to implement support for it
on the wire protocol and in revlogs.
$ cat << EOF >> $HGRCPATH
> [format]
> usegeneraldelta=yes
> EOF
bundle w/o type option
$ hg init t1
$ hg init t2
$ cd t1
$ echo blablablablabla > file.txt
$ hg ci -Ama
adding file.txt
$ hg log | grep summary
summary: a
$ hg bundle ../b1 ../t2
searching for changes
1 changesets found
$ cd ../t2
$ hg pull ../b1
pulling from ../b1
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
(run 'hg update' to get a working copy)
$ hg up
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg log | grep summary
summary: a
$ cd ..
test bundle types
$ testbundle() {
> echo % test bundle type $1
> hg init t$1
> cd t1
> hg bundle -t $1 ../b$1 ../t$1
> f -q -B6 -D ../b$1; echo
> cd ../t$1
> hg debugbundle ../b$1
> hg debugbundle --spec ../b$1
> echo
> cd ..
> }
$ for t in "None" "bzip2" "gzip" "none-v2" "v2" "v1" "gzip-v1"; do
> testbundle $t
> done
% test bundle type None
searching for changes
1 changesets found
HG20\x00\x00 (esc)
Stream params: {}
changegroup -- "sortdict([('version', '02'), ('nbchanges', '1')])"
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
none-v2
% test bundle type bzip2
searching for changes
1 changesets found
HG20\x00\x00 (esc)
Stream params: sortdict([('Compression', 'BZ')])
changegroup -- "sortdict([('version', '02'), ('nbchanges', '1')])"
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
bzip2-v2
% test bundle type gzip
searching for changes
1 changesets found
HG20\x00\x00 (esc)
Stream params: sortdict([('Compression', 'GZ')])
changegroup -- "sortdict([('version', '02'), ('nbchanges', '1')])"
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
gzip-v2
% test bundle type none-v2
searching for changes
1 changesets found
HG20\x00\x00 (esc)
Stream params: {}
changegroup -- "sortdict([('version', '02'), ('nbchanges', '1')])"
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
none-v2
% test bundle type v2
searching for changes
1 changesets found
HG20\x00\x00 (esc)
Stream params: sortdict([('Compression', 'BZ')])
changegroup -- "sortdict([('version', '02'), ('nbchanges', '1')])"
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
bzip2-v2
% test bundle type v1
searching for changes
1 changesets found
HG10BZ
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
bzip2-v1
% test bundle type gzip-v1
searching for changes
1 changesets found
HG10GZ
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
gzip-v1
#if zstd
$ for t in "zstd" "zstd-v2"; do
> testbundle $t
> done
% test bundle type zstd
searching for changes
1 changesets found
HG20\x00\x00 (esc)
Stream params: sortdict([('Compression', 'ZS')])
changegroup -- "sortdict([('version', '02'), ('nbchanges', '1')])"
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
zstd-v2
% test bundle type zstd-v2
searching for changes
1 changesets found
HG20\x00\x00 (esc)
Stream params: sortdict([('Compression', 'ZS')])
changegroup -- "sortdict([('version', '02'), ('nbchanges', '1')])"
c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
zstd-v2
#else
zstd is a valid engine but isn't available
$ hg -R t1 bundle -a -t zstd irrelevant.hg
abort: compression engine zstd could not be loaded
[255]
#endif
test garbage file
$ echo garbage > bgarbage
$ hg init tgarbage
$ cd tgarbage
$ hg pull ../bgarbage
pulling from ../bgarbage
abort: ../bgarbage: not a Mercurial bundle
[255]
$ cd ..
test invalid bundle type
$ cd t1
$ hg bundle -a -t garbage ../bgarbage
abort: garbage is not a recognized bundle specification
(see 'hg help bundle' for supported values for --type)
[255]
$ cd ..