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 adding .hgeol
$ cat >> $HGRCPATH <<EOF
> [diff]
> git = 1
> EOF
$ seteol () {
> if [ $1 = "LF" ]; then
> EOL='\n'
> else
> EOL='\r\n'
> fi
> }
$ makerepo () {
> echo
> echo "# ==== setup repository ===="
> echo '% hg init'
> hg init repo
> cd repo
> printf "first\nsecond\nthird\n" > a.txt
> hg commit -d '100 0' --addremove -m 'LF commit'
> cd ..
> }
$ dotest () {
> seteol $1
> echo
> echo "% hg clone repo repo-$1"
> hg clone repo repo-$1
> cd repo-$1
> cat > .hg/hgrc <<EOF
> [extensions]
> eol =
> [eol]
> native = LF
> EOF
> cat > .hgeol <<EOF
> [patterns]
> **.txt = native
> [repository]
> native = $1
> EOF
> echo '% hg add .hgeol'
> hg add .hgeol
> echo '% hg status'
> hg status
> echo '% hg commit'
> hg commit -d '200 0' -m 'Added .hgeol file'
> echo '% hg status'
> hg status
> echo '% hg tip -p'
> hg tip -p
> cd ..
> rm -r repo-$1
> }
$ makerepo
# ==== setup repository ====
% hg init
adding a.txt
$ dotest LF
% hg clone repo repo-LF
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% hg add .hgeol
% hg status
A .hgeol
% hg commit
% hg status
% hg tip -p
changeset: 1:33503edb53b0
tag: tip
user: test
date: Thu Jan 01 00:03:20 1970 +0000
summary: Added .hgeol file
diff --git a/.hgeol b/.hgeol
new file mode 100644
--- /dev/null
+++ b/.hgeol
@@ -0,0 +1,4 @@
+[patterns]
+**.txt = native
+[repository]
+native = LF
$ dotest CRLF
% hg clone repo repo-CRLF
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% hg add .hgeol
% hg status
M a.txt
A .hgeol
% hg commit
% hg status
% hg tip -p
changeset: 1:6e64eaa9eb23
tag: tip
user: test
date: Thu Jan 01 00:03:20 1970 +0000
summary: Added .hgeol file
diff --git a/.hgeol b/.hgeol
new file mode 100644
--- /dev/null
+++ b/.hgeol
@@ -0,0 +1,4 @@
+[patterns]
+**.txt = native
+[repository]
+native = CRLF
diff --git a/a.txt b/a.txt
--- a/a.txt
+++ b/a.txt
@@ -1,3 +1,3 @@
-first
-second
-third
+first\r (esc)
+second\r (esc)
+third\r (esc)
$ rm -r repo