cborutil: change buffering strategy
Profiling revealed that we were spending a lot of time on the
line that was concatenating the old buffer with the incoming data
when attempting to decode long byte strings, such as manifest
revisions.
Essentially, we were feeding N chunks of size len(X) << len(Y) into
decode() and continuously allocating a new, larger buffer to hold
the undecoded input. This created substantial memory churn and
slowed down execution.
Changing the code to aggregate pending chunks in a list until we
have enough data to fully decode the next atom makes things much
more efficient.
I don't have exact data, but I recall the old code spending >1s
on manifest fulltexts from the mozilla-unified repo. The new code
doesn't significantly appear in profile output.
Differential Revision: https://phab.mercurial-scm.org/D4854
test children command
$ cat <<EOF >> $HGRCPATH
> [extensions]
> children =
> EOF
init
$ hg init t
$ cd t
no working directory
$ hg children
setup
$ echo 0 > file0
$ hg ci -qAm 0 -d '0 0'
$ echo 1 > file1
$ hg ci -qAm 1 -d '1 0'
$ echo 2 >> file0
$ hg ci -qAm 2 -d '2 0'
$ hg co null
0 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ echo 3 > file3
$ hg ci -qAm 3 -d '3 0'
hg children at revision 3 (tip)
$ hg children
$ hg co null
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
hg children at nullrev (should be 0 and 3)
$ hg children
changeset: 0:4df8521a7374
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 0
changeset: 3:e2962852269d
tag: tip
parent: -1:000000000000
user: test
date: Thu Jan 01 00:00:03 1970 +0000
summary: 3
$ hg co 1
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
hg children at revision 1 (should be 2)
$ hg children
changeset: 2:8f5eea5023c2
user: test
date: Thu Jan 01 00:00:02 1970 +0000
summary: 2
$ hg co 2
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
hg children at revision 2 (other head)
$ hg children
$ for i in null 0 1 2 3 '2^'; do
> echo "hg children -r '$i'"
> hg children -r $i
> done
hg children -r 'null'
changeset: 0:4df8521a7374
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 0
changeset: 3:e2962852269d
tag: tip
parent: -1:000000000000
user: test
date: Thu Jan 01 00:00:03 1970 +0000
summary: 3
hg children -r '0'
changeset: 1:708c093edef0
user: test
date: Thu Jan 01 00:00:01 1970 +0000
summary: 1
hg children -r '1'
changeset: 2:8f5eea5023c2
user: test
date: Thu Jan 01 00:00:02 1970 +0000
summary: 2
hg children -r '2'
hg children -r '3'
hg children -r '2^'
changeset: 2:8f5eea5023c2
user: test
date: Thu Jan 01 00:00:02 1970 +0000
summary: 2
hg children -r 0 file0 (should be 2)
$ hg children -r 0 file0
changeset: 2:8f5eea5023c2
user: test
date: Thu Jan 01 00:00:02 1970 +0000
summary: 2
hg children -r 1 file0 (should be 2)
$ hg children -r 1 file0
changeset: 2:8f5eea5023c2
user: test
date: Thu Jan 01 00:00:02 1970 +0000
summary: 2
$ hg co 0
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
hg children file0 at revision 0 (should be 2)
$ hg children file0
changeset: 2:8f5eea5023c2
user: test
date: Thu Jan 01 00:00:02 1970 +0000
summary: 2
should be compatible with templater (don't pass fctx to displayer)
$ hg children file0 -Tdefault
changeset: 2:8f5eea5023c2
user: test
date: Thu Jan 01 00:00:02 1970 +0000
summary: 2
$ cd ..