snapshot: also consider the snapshot chain of one unrelated revision
To maximize the chance of good delta chain reuse, we inject an unrelated delta
chain into our search. To do so, we search for the highest revision unrelated
to the parents of the current revision and use its snapshot chain too.
Adding this extra snapshot into the mix can have a performance impact. We'll
deal with performance impact in a later series.
====================================
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 echo 'skipped: outdated artifact, md5 "'"$currenthash"'" expected "'"$expectedhash"'" run "'"$TESTDIR"'/artifacts/scripts/generate-churning-bundle.py"'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=59230936
$ 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 : 176 ( 3.52%)
lvl-0 : 3 ( 0.06%)
lvl-1 : 17 ( 0.34%)
lvl-2 : 45 ( 0.90%)
lvl-3 : 56 ( 1.12%)
lvl-4 : 55 ( 1.10%)
deltas : 4825 (96.48%)
revision size : 59230936
snapshot : 5770371 ( 9.74%)
lvl-0 : 602962 ( 1.02%)
lvl-1 : 1534153 ( 2.59%)
lvl-2 : 1604445 ( 2.71%)
lvl-3 : 1218174 ( 2.06%)
lvl-4 : 810637 ( 1.37%)
deltas : 53460565 (90.26%)
chunks : 5001
0x78 (x) : 5001 (100.00%)
chunks size : 59230936
0x78 (x) : 59230936 (100.00%)
avg chain length : 17
max chain length : 45
max chain reach : 25326012
compression ratio : 29
uncompressed data size (min/max/avg) : 346468 / 346472 / 346471
full revision size (min/max/avg) : 200897 / 201050 / 200987
inter-snapshot size (min/max/avg) : 11598 / 171990 / 29869
level-1 (min/max/avg) : 14037 / 171990 / 90244
level-2 (min/max/avg) : 11632 / 84456 / 35654
level-3 (min/max/avg) : 11598 / 41486 / 21753
level-4 (min/max/avg) : 11618 / 19913 / 14738
delta size (min/max/avg) : 10649 / 105209 / 11079
deltas against prev : 4156 (86.13%)
where prev = p1 : 4120 (99.13%)
where prev = p2 : 0 ( 0.00%)
other : 36 ( 0.87%)
deltas against p1 : 646 (13.39%)
deltas against p2 : 23 ( 0.48%)
deltas against other : 0 ( 0.00%)