revlog: always enable generaldelta on version 2 revlogs
This commit starts the process of diverging version 2 revlogs
from version 1 revlogs.
generaldelta is a useful feature and has been enabled by
default for ages. I can't think of a good reason why the
feature should be disabled. Yes, it is true changelogs
today don't have generaldelta enabled. But that's because
they don't have delta chains enabled, so generaldelta makes
no sense there.
This commit makes generaldelta always enabled on version 2
revlogs.
As part of this, one-off code in changelog.py mucking with
revlog.version had to be made conditional on the revlog
version, as we don't want to change revlog feature
flags on version 2 revlogs. The fact this code exists
is horrible and stems from revlog options being shared by
the opener. We probably want a better API here. But that can
wait for another patch.
Differential Revision: https://phab.mercurial-scm.org/D5561
====================================
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 echo 'skipped: outdated artifact, md5 "'"$currenthash"'" expected "'"$expectedhash"'" run "'"$TESTDIR"'/artifacts/scripts/generate-churning-bundle.py"'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
> maxchainlen = 15
> [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=63002924
$ 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 : 374 ( 7.48%)
lvl-0 : 4 ( 0.08%)
lvl-1 : 23 ( 0.46%)
lvl-2 : 63 ( 1.26%)
lvl-3 : 118 ( 2.36%)
lvl-4 : 166 ( 3.32%)
deltas : 4627 (92.52%)
revision size : 63002924
snapshot : 9888099 (15.69%)
lvl-0 : 804262 ( 1.28%)
lvl-1 : 1561380 ( 2.48%)
lvl-2 : 2096696 ( 3.33%)
lvl-3 : 2749539 ( 4.36%)
lvl-4 : 2676222 ( 4.25%)
deltas : 53114825 (84.31%)
chunks : 5001
0x78 (x) : 5001 (100.00%)
chunks size : 63002924
0x78 (x) : 63002924 (100.00%)
avg chain length : 9
max chain length : 15
max chain reach : 28907121
compression ratio : 27
uncompressed data size (min/max/avg) : 346468 / 346472 / 346471
full revision size (min/max/avg) : 201008 / 201141 / 201065
inter-snapshot size (min/max/avg) : 11601 / 157413 / 24550
level-1 (min/max/avg) : 13061 / 157413 / 67886
level-2 (min/max/avg) : 11674 / 85631 / 33280
level-3 (min/max/avg) : 11602 / 42957 / 23301
level-4 (min/max/avg) : 11601 / 21475 / 16121
delta size (min/max/avg) : 10649 / 105465 / 11479
deltas against prev : 3966 (85.71%)
where prev = p1 : 3922 (98.89%)
where prev = p2 : 0 ( 0.00%)
other : 44 ( 1.11%)
deltas against p1 : 611 (13.21%)
deltas against p2 : 50 ( 1.08%)
deltas against other : 0 ( 0.00%)