sparse-revlog: add a test checking revlog deltas for a churning file
The test repository contains 5000 revisions and is therefore slow to build:
five minutes with CHG, over fifteen minutes without. It is too slow to build
during the test. Bundling all content produce a sizeable result, 20BM, too
large to be committed. Instead, we commit a script to build the expected
bundle and the test checks if the bundle is available. Any run of the script
will produce the same repository content, using resulting in the same hashes.
Using smaller repositories was tried, however, it misses most of the cases we
are planning to improve. Having them in a 5000 repository is already nice, we
usually see these case in repositories in the order of magnitude of one
million revisions.
This test will be very useful to check various changes strategy for building
delta to store in a sparse-revlog.
In this series we will focus our attention on the following metrics:
The ones that will impact the final storage performance (size, space):
* size of the revlog data file (".hg/store/data/*.d")
* chain length info
The ones that describe the deltas patterns:
* number of snapshot revision (and their level)
* size taken by snapshot revision (and their level)
====================================
Test delta choice with sparse revlog
====================================
Sparse-revlog usually shows the most gain on Manifest. However, it is simpler
to general an appropriate file, so we test with a single file instead. The
goal is to observe intermediate snapshot being created.
We need a large enough file. Part of the content needs to be replaced
repeatedly while some of it changes rarely.
$ bundlepath="$TESTDIR/artifacts/cache/big-file-churn.hg"
$ expectedhash=`cat "$bundlepath".md5`
$ if [ ! -f "$bundlepath" ]; then
> echo 'skipped: missing artifact, run "'"$TESTDIR"'/artifacts/scripts/generate-churning-bundle.py"'
> exit 80
> fi
$ currenthash=`f -M "$bundlepath" | cut -d = -f 2`
$ if [ "$currenthash" != "$expectedhash" ]; then
> echo 'skipped: outdated artifact, md5 "'"$currenthash"'" expected "'"$expectedhash"'" run "'"$TESTDIR"'/artifacts/scripts/generate-churning-bundle.py"'
> exit 80
> fi
$ cat >> $HGRCPATH << EOF
> [format]
> sparse-revlog = yes
> [storage]
> revlog.optimize-delta-parent-choice = yes
> EOF
$ hg init sparse-repo
$ cd sparse-repo
$ hg unbundle $bundlepath
adding changesets
adding manifests
adding file changes
added 5001 changesets with 5001 changes to 1 files (+89 heads)
new changesets 9706f5af64f4:d9032adc8114 (5001 drafts)
(run 'hg heads' to see heads, 'hg merge' to merge)
$ hg up
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
updated to "d9032adc8114: commit #5000"
89 other heads for branch "default"
$ hg log --stat -r 0:3
changeset: 0:9706f5af64f4
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: initial commit
SPARSE-REVLOG-TEST-FILE | 10500 ++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 10500 insertions(+), 0 deletions(-)
changeset: 1:724907deaa5e
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: commit #1
SPARSE-REVLOG-TEST-FILE | 1068 +++++++++++++++++++++++-----------------------
1 files changed, 534 insertions(+), 534 deletions(-)
changeset: 2:62c41bce3e5d
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: commit #2
SPARSE-REVLOG-TEST-FILE | 1068 +++++++++++++++++++++++-----------------------
1 files changed, 534 insertions(+), 534 deletions(-)
changeset: 3:348a9cbd6959
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: commit #3
SPARSE-REVLOG-TEST-FILE | 1068 +++++++++++++++++++++++-----------------------
1 files changed, 534 insertions(+), 534 deletions(-)
$ f -s .hg/store/data/*.d
.hg/store/data/_s_p_a_r_s_e-_r_e_v_l_o_g-_t_e_s_t-_f_i_l_e.d: size=74365490
$ hg debugrevlog *
format : 1
flags : generaldelta
revisions : 5001
merges : 625 (12.50%)
normal : 4376 (87.50%)
revisions : 5001
empty : 0 ( 0.00%)
text : 0 (100.00%)
delta : 0 (100.00%)
snapshot : 101 ( 2.02%)
lvl-0 : 101 ( 2.02%)
deltas : 4900 (97.98%)
revision size : 74365490
snapshot : 20307865 (27.31%)
lvl-0 : 20307865 (27.31%)
deltas : 54057625 (72.69%)
chunks : 5001
0x78 (x) : 5001 (100.00%)
chunks size : 74365490
0x78 (x) : 74365490 (100.00%)
avg chain length : 23
max chain length : 45
max chain reach : 11039464
compression ratio : 23
uncompressed data size (min/max/avg) : 346468 / 346472 / 346471
full revision size (min/max/avg) : 200927 / 201202 / 201067
inter-snapshot size (min/max/avg) : 0 / 0 / 0
delta size (min/max/avg) : 10649 / 103898 / 11032
deltas against prev : 4231 (86.35%)
where prev = p1 : 4172 (98.61%)
where prev = p2 : 0 ( 0.00%)
other : 59 ( 1.39%)
deltas against p1 : 651 (13.29%)
deltas against p2 : 18 ( 0.37%)
deltas against other : 0 ( 0.00%)