snapshot: refine candidate snapshot base upward
Once we found a suitable snapshot base it is useful to check if it has a
"children" snapshot that would provide a better diff. This is useful when base
not directly related to stored revision are picked. In those case, we "jumped"
to this new chain at an arbitrary point, checking if a higher point is more
appropriate will help to provide better results and increase snapshot reuse.
====================================
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 echo 'skipped: outdated artifact, md5 "'"$currenthash"'" expected "'"$expectedhash"'" run "'"$TESTDIR"'/artifacts/scripts/generate-churning-bundle.py"'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=59302280
$ 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 : 168 ( 3.36%)
lvl-0 : 4 ( 0.08%)
lvl-1 : 18 ( 0.36%)
lvl-2 : 39 ( 0.78%)
lvl-3 : 54 ( 1.08%)
lvl-4 : 53 ( 1.06%)
deltas : 4833 (96.64%)
revision size : 59302280
snapshot : 5833942 ( 9.84%)
lvl-0 : 804068 ( 1.36%)
lvl-1 : 1378470 ( 2.32%)
lvl-2 : 1608138 ( 2.71%)
lvl-3 : 1222158 ( 2.06%)
lvl-4 : 821108 ( 1.38%)
deltas : 53468338 (90.16%)
chunks : 5001
0x78 (x) : 5001 (100.00%)
chunks size : 59302280
0x78 (x) : 59302280 (100.00%)
avg chain length : 17
max chain length : 45
max chain reach : 22744720
compression ratio : 29
uncompressed data size (min/max/avg) : 346468 / 346472 / 346471
full revision size (min/max/avg) : 200985 / 201050 / 201017
inter-snapshot size (min/max/avg) : 11598 / 163304 / 30669
level-1 (min/max/avg) : 15616 / 163304 / 76581
level-2 (min/max/avg) : 11602 / 86428 / 41234
level-3 (min/max/avg) : 11598 / 42390 / 22632
level-4 (min/max/avg) : 11603 / 19649 / 15492
delta size (min/max/avg) : 10649 / 105465 / 11063
deltas against prev : 4167 (86.22%)
where prev = p1 : 4129 (99.09%)
where prev = p2 : 0 ( 0.00%)
other : 38 ( 0.91%)
deltas against p1 : 643 (13.30%)
deltas against p2 : 23 ( 0.48%)
deltas against other : 0 ( 0.00%)