Mercurial > hg
view tests/test-clone-r.t @ 30442:41a8106789ca
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.
| author | Gregory Szorc <gregory.szorc@gmail.com> |
|---|---|
| date | Fri, 11 Nov 2016 01:10:07 -0800 |
| parents | b87b252415ad |
| children | eb586ed5d8ce |
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$ hg init test $ cd test $ echo 0 >> afile $ hg add afile $ hg commit -m "0.0" $ echo 1 >> afile $ hg commit -m "0.1" $ echo 2 >> afile $ hg commit -m "0.2" $ echo 3 >> afile $ hg commit -m "0.3" $ hg update -C 0 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ echo 1 >> afile $ hg commit -m "1.1" created new head $ echo 2 >> afile $ hg commit -m "1.2" $ echo a line > fred $ echo 3 >> afile $ hg add fred $ hg commit -m "1.3" $ hg mv afile adifferentfile $ hg commit -m "1.3m" $ hg update -C 3 1 files updated, 0 files merged, 2 files removed, 0 files unresolved $ hg mv afile anotherfile $ hg commit -m "0.3m" $ hg debugindex -f 1 afile rev flag offset length size ..... link p1 p2 nodeid (re) 0 0000 0 3 2 ..... 0 -1 -1 362fef284ce2 (re) 1 0000 3 5 4 ..... 1 0 -1 125144f7e028 (re) 2 0000 8 7 6 ..... 2 1 -1 4c982badb186 (re) 3 0000 15 9 8 ..... 3 2 -1 19b1fc555737 (re) $ hg debugindex adifferentfile rev offset length ..... linkrev nodeid p1 p2 (re) 0 0 75 ..... 7 2565f3199a74 000000000000 000000000000 (re) $ hg debugindex anotherfile rev offset length ..... linkrev nodeid p1 p2 (re) 0 0 75 ..... 8 2565f3199a74 000000000000 000000000000 (re) $ hg debugindex fred rev offset length ..... linkrev nodeid p1 p2 (re) 0 0 8 ..... 6 12ab3bcc5ea4 000000000000 000000000000 (re) $ hg debugindex --manifest rev offset length ..... linkrev nodeid p1 p2 (re) 0 0 48 ..... 0 43eadb1d2d06 000000000000 000000000000 (re) 1 48 48 ..... 1 8b89697eba2c 43eadb1d2d06 000000000000 (re) 2 96 48 ..... 2 626a32663c2f 8b89697eba2c 000000000000 (re) 3 144 48 ..... 3 f54c32f13478 626a32663c2f 000000000000 (re) 4 192 .. ..... 6 de68e904d169 626a32663c2f 000000000000 (re) 5 2.. .. ..... 7 09bb521d218d de68e904d169 000000000000 (re) 6 3.. 54 ..... 8 1fde233dfb0f f54c32f13478 000000000000 (re) $ hg verify checking changesets checking manifests crosschecking files in changesets and manifests checking files 4 files, 9 changesets, 7 total revisions $ cd .. $ for i in 0 1 2 3 4 5 6 7 8; do > echo > echo ---- hg clone -r "$i" test test-"$i" > hg clone -r "$i" test test-"$i" > cd test-"$i" > hg verify > cd .. > done ---- hg clone -r 0 test test-0 adding changesets adding manifests adding file changes added 1 changesets with 1 changes to 1 files updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved checking changesets checking manifests crosschecking files in changesets and manifests checking files 1 files, 1 changesets, 1 total revisions ---- hg clone -r 1 test test-1 adding changesets adding manifests adding file changes added 2 changesets with 2 changes to 1 files updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved checking changesets checking manifests crosschecking files in changesets and manifests checking files 1 files, 2 changesets, 2 total revisions ---- hg clone -r 2 test test-2 adding changesets adding manifests adding file changes added 3 changesets with 3 changes to 1 files updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved checking changesets checking manifests crosschecking files in changesets and manifests checking files 1 files, 3 changesets, 3 total revisions ---- hg clone -r 3 test test-3 adding changesets adding manifests adding file changes added 4 changesets with 4 changes to 1 files updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved checking changesets checking manifests crosschecking files in changesets and manifests checking files 1 files, 4 changesets, 4 total revisions ---- hg clone -r 4 test test-4 adding changesets adding manifests adding file changes added 2 changesets with 2 changes to 1 files updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved checking changesets checking manifests crosschecking files in changesets and manifests checking files 1 files, 2 changesets, 2 total revisions ---- hg clone -r 5 test test-5 adding changesets adding manifests adding file changes added 3 changesets with 3 changes to 1 files updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved checking changesets checking manifests crosschecking files in changesets and manifests checking files 1 files, 3 changesets, 3 total revisions ---- hg clone -r 6 test test-6 adding changesets adding manifests adding file changes added 4 changesets with 5 changes to 2 files updating to branch default 2 files updated, 0 files merged, 0 files removed, 0 files unresolved checking changesets checking manifests crosschecking files in changesets and manifests checking files 2 files, 4 changesets, 5 total revisions ---- hg clone -r 7 test test-7 adding changesets adding manifests adding file changes added 5 changesets with 6 changes to 3 files updating to branch default 2 files updated, 0 files merged, 0 files removed, 0 files unresolved checking changesets checking manifests crosschecking files in changesets and manifests checking files 3 files, 5 changesets, 6 total revisions ---- hg clone -r 8 test test-8 adding changesets adding manifests adding file changes added 5 changesets with 5 changes to 2 files updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved checking changesets checking manifests crosschecking files in changesets and manifests checking files 2 files, 5 changesets, 5 total revisions $ cd test-8 $ hg pull ../test-7 pulling from ../test-7 searching for changes adding changesets adding manifests adding file changes added 4 changesets with 2 changes to 3 files (+1 heads) (run 'hg heads' to see heads, 'hg merge' to merge) $ hg verify checking changesets checking manifests crosschecking files in changesets and manifests checking files 4 files, 9 changesets, 7 total revisions $ cd .. $ hg clone test test-9 updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ cd test-9 $ hg branch foobar marked working directory as branch foobar (branches are permanent and global, did you want a bookmark?) $ echo file2 >> file2 $ hg add file2 $ hg commit -m "changeset9" $ echo file3 >> file3 $ hg add file3 $ hg commit -m "changeset10" $ cd .. $ hg clone -r 9 -u foobar test-9 test-10 adding changesets adding manifests adding file changes added 6 changesets with 6 changes to 3 files updating to branch foobar 2 files updated, 0 files merged, 0 files removed, 0 files unresolved