util: improve iterfile so it chooses code path wisely
We have performance concerns on "iterfile" as it is 4X slower on normal
files. While modern systems have the nice property that reading a "fast"
(on-disk) file cannot be interrupted and should be made use of.
This patch dumps the related knowledge in comments. And "iterfile" chooses
code paths wisely:
1. If it's CPython 3, or PyPY, use the fast path.
2. If fp is a normal file, use the fast path.
3. If fp is not a normal file and CPython version >= 2.7.4, use the same
workaround (4x slower) as before.
4. If fp is not a normal file and CPython version < 2.7.4, use another
workaround (2x slower but may block longer then necessary) which
basically re-invents the buffer + readline logic in Python.
This will give us good confidence on both correctness and performance
dealing with EINTR in iterfile(fp) for all known supported Python versions.
#require execbit
$ umask 027
$ hg init test1
$ cd test1
$ touch a b
$ hg add a b
$ hg ci -m "added a b"
$ cd ..
$ hg clone test1 test3
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg init test2
$ cd test2
$ hg pull ../test1
pulling from ../test1
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 2 changes to 2 files
(run 'hg update' to get a working copy)
$ hg co
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ chmod +x a
$ hg ci -m "chmod +x a"
the changelog should mention file a:
$ hg tip --template '{files}\n'
a
$ cd ../test1
$ echo 123 >>a
$ hg ci -m "a updated"
$ hg pull ../test2
pulling from ../test2
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 0 changes to 0 files (+1 heads)
(run 'hg heads' to see heads, 'hg merge' to merge)
$ hg heads
changeset: 2:7f4313b42a34
tag: tip
parent: 0:22a449e20da5
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: chmod +x a
changeset: 1:c6ecefc45368
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: a updated
$ hg history
changeset: 2:7f4313b42a34
tag: tip
parent: 0:22a449e20da5
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: chmod +x a
changeset: 1:c6ecefc45368
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: a updated
changeset: 0:22a449e20da5
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: added a b
$ hg -v merge
resolving manifests
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat a
123
$ [ -x a ]
$ cd ../test3
$ echo 123 >>b
$ hg ci -m "b updated"
$ hg pull ../test2
pulling from ../test2
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 0 changes to 0 files (+1 heads)
(run 'hg heads' to see heads, 'hg merge' to merge)
$ hg heads
changeset: 2:7f4313b42a34
tag: tip
parent: 0:22a449e20da5
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: chmod +x a
changeset: 1:dc57ead75f79
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: b updated
$ hg history
changeset: 2:7f4313b42a34
tag: tip
parent: 0:22a449e20da5
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: chmod +x a
changeset: 1:dc57ead75f79
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: b updated
changeset: 0:22a449e20da5
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: added a b
$ hg -v merge
resolving manifests
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ ls -l ../test[123]/a > foo
$ cut -b 1-10 < foo
-rwxr-x---
-rwxr-x---
-rwxr-x---
$ hg debugindex a
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 0 ..... 0 b80de5d13875 000000000000 000000000000 (re)
$ hg debugindex -R ../test2 a
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 0 ..... 0 b80de5d13875 000000000000 000000000000 (re)
$ hg debugindex -R ../test1 a
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 0 ..... 0 b80de5d13875 000000000000 000000000000 (re)
1 0 5 ..... 1 7fe919cc0336 b80de5d13875 000000000000 (re)
$ cd ..