bundle2: implement consume() API on unbundlepart
We want bundle parts to not be seekable by default. That means
eliminating the generic seek() method.
A common pattern in bundle2.py is to seek to the end of the part
data. This is mainly used by the part iteration code to ensure
the underlying stream is advanced to the next bundle part.
In this commit, we establish a dedicated API for consuming a
bundle2 part data. We switch users of seek() to it.
The old implementation of seek(0, os.SEEK_END) would effectively
call self.read(). The new implementation calls self.read(32768)
in a loop. The old implementation would therefore assemble a
buffer to hold all remaining data being seeked over. For seeking
over large bundle parts, this would involve a large allocation and
a lot of overhead to collect intermediate data! This overhead can
be seen in the results for `hg perfbundleread`:
! bundle2 iterparts()
! wall 10.891305 comb 10.820000 user 7.990000 sys 2.830000 (best of 3)
! wall 8.070791 comb 8.060000 user 7.180000 sys 0.880000 (best of 3)
! bundle2 part seek()
! wall 12.991478 comb 10.390000 user 7.720000 sys 2.670000 (best of 3)
! wall 10.370142 comb 10.350000 user 7.430000 sys 2.920000 (best of 3)
Of course, skipping over large payload data isn't likely very common.
So I doubt the performance wins will be observed in the wild.
Differential Revision: https://phab.mercurial-scm.org/D1388
test stripping of filelogs where the linkrev doesn't always increase
$ echo '[extensions]' >> $HGRCPATH
$ echo 'strip =' >> $HGRCPATH
$ hg init orig
$ cd orig
$ commit()
> {
> hg up -qC null
> count=1
> for i in "$@"; do
> for f in $i; do
> echo $count > $f
> done
> count=`expr $count + 1`
> done
> hg commit -qAm "$*"
> }
2 1 0 2 0 1 2
$ commit '201 210'
$ commit '102 120' '210'
$ commit '021'
$ commit '201' '021 120'
$ commit '012 021' '102 201' '120 210'
$ commit 'manifest-file'
$ commit '102 120' '012 210' '021 201'
$ commit '201 210' '021 120' '012 102'
$ HGUSER=another-user; export HGUSER
$ commit 'manifest-file'
$ commit '012' 'manifest-file'
$ cd ..
$ hg clone -q -U -r -1 -r -2 -r -3 -r -4 -r -6 orig crossed
$ cd crossed
$ hg debugindex --manifest
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 112 ..... 0 6f105cbb914d 000000000000 000000000000 (re)
1 112 56 ..... 3 1b55917b3699 000000000000 000000000000 (re)
2 168 123 ..... 1 8f3d04e263e5 000000000000 000000000000 (re)
3 291 122 ..... 2 f0ef8726ac4f 000000000000 000000000000 (re)
4 413 87 ..... 4 0b76e38b4070 000000000000 000000000000 (re)
$ for i in 012 021 102 120 201 210 manifest-file; do
> echo $i
> hg debugindex $i
> echo
> done
012
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 3 ..... 0 b8e02f643373 000000000000 000000000000 (re)
1 3 3 ..... 1 5d9299349fc0 000000000000 000000000000 (re)
2 6 3 ..... 2 2661d26c6496 000000000000 000000000000 (re)
021
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 3 ..... 0 b8e02f643373 000000000000 000000000000 (re)
1 3 3 ..... 2 5d9299349fc0 000000000000 000000000000 (re)
2 6 3 ..... 1 2661d26c6496 000000000000 000000000000 (re)
102
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 3 ..... 1 b8e02f643373 000000000000 000000000000 (re)
1 3 3 ..... 0 5d9299349fc0 000000000000 000000000000 (re)
2 6 3 ..... 2 2661d26c6496 000000000000 000000000000 (re)
120
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 3 ..... 1 b8e02f643373 000000000000 000000000000 (re)
1 3 3 ..... 2 5d9299349fc0 000000000000 000000000000 (re)
2 6 3 ..... 0 2661d26c6496 000000000000 000000000000 (re)
201
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 3 ..... 2 b8e02f643373 000000000000 000000000000 (re)
1 3 3 ..... 0 5d9299349fc0 000000000000 000000000000 (re)
2 6 3 ..... 1 2661d26c6496 000000000000 000000000000 (re)
210
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 3 ..... 2 b8e02f643373 000000000000 000000000000 (re)
1 3 3 ..... 1 5d9299349fc0 000000000000 000000000000 (re)
2 6 3 ..... 0 2661d26c6496 000000000000 000000000000 (re)
manifest-file
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 3 ..... 3 b8e02f643373 000000000000 000000000000 (re)
1 3 3 ..... 4 5d9299349fc0 000000000000 000000000000 (re)
$ cd ..
$ for i in 0 1 2 3 4; do
> hg clone -q -U --pull crossed $i
> echo "% Trying to strip revision $i"
> hg --cwd $i strip $i
> echo "% Verifying"
> hg --cwd $i verify
> echo
> done
% Trying to strip revision 0
saved backup bundle to $TESTTMP/0/.hg/strip-backup/*-backup.hg (glob)
% Verifying
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
7 files, 4 changesets, 15 total revisions
% Trying to strip revision 1
saved backup bundle to $TESTTMP/1/.hg/strip-backup/*-backup.hg (glob)
% Verifying
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
7 files, 4 changesets, 14 total revisions
% Trying to strip revision 2
saved backup bundle to $TESTTMP/2/.hg/strip-backup/*-backup.hg (glob)
% Verifying
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
7 files, 4 changesets, 14 total revisions
% Trying to strip revision 3
saved backup bundle to $TESTTMP/3/.hg/strip-backup/*-backup.hg (glob)
% Verifying
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
7 files, 4 changesets, 19 total revisions
% Trying to strip revision 4
saved backup bundle to $TESTTMP/4/.hg/strip-backup/*-backup.hg (glob)
% Verifying
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
7 files, 4 changesets, 19 total revisions