Mercurial > hg
view tests/test-merge-commit.t @ 38732:be4984261611
merge: mark file gets as not thread safe (issue5933)
In default installs, this has the effect of disabling the thread-based
worker on Windows when manifesting files in the working directory. My
measurements have shown that with revlog-based repositories, Mercurial
spends a lot of CPU time in revlog code resolving file data. This ends
up incurring a lot of context switching across threads and slows down
`hg update` operations when going from an empty working directory to
the tip of the repo.
On mozilla-unified (246,351 files) on an i7-6700K (4+4 CPUs):
before: 487s wall
after: 360s wall (equivalent to worker.enabled=false)
cpus=2: 379s wall
Even with only 2 threads, the thread pool is still slower.
The introduction of the thread-based worker (02b36e860e0b) states that
it resulted in a "~50%" speedup for `hg sparse --enable-profile` and
`hg sparse --disable-profile`. This disagrees with my measurement
above. I theorize a few reasons for this:
1) Removal of files from the working directory is I/O - not CPU - bound
and should benefit from a thread pool (unless I/O is insanely fast
and the GIL release is near instantaneous). So tests like `hg sparse
--enable-profile` may exercise deletion throughput and aren't good
benchmarks for worker tasks that are CPU heavy.
2) The patch was authored by someone at Facebook. The results were
likely measured against a repository using remotefilelog. And I
believe that revision retrieval during working directory updates with
remotefilelog will often use a remote store, thus being I/O and not
CPU bound. This probably resulted in an overstated performance gain.
Since there appears to be a need to enable the thread-based worker with
some stores, I've made the flagging of file gets as thread safe
configurable. I've made it experimental because I don't want to formalize
a boolean flag for this option and because this attribute is best
captured against the store implementation. But we don't have a proper
store API for this yet. I'd rather cross this bridge later.
It is possible there are revlog-based repositories that do benefit from
a thread-based worker. I didn't do very comprehensive testing. If there
are, we may want to devise a more proper algorithm for whether to use
the thread-based worker, including possibly config options to limit the
number of threads to use. But until I see evidence that justifies
complexity, simplicity wins.
Differential Revision: https://phab.mercurial-scm.org/D3963
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Wed, 18 Jul 2018 09:49:34 -0700 |
parents | d4e62df1c73d |
children | 91a0bc50b288 |
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Check that renames are correctly saved by a commit after a merge Test with the merge on 3 having the rename on the local parent $ hg init a $ cd a $ echo line1 > foo $ hg add foo $ hg ci -m '0: add foo' $ echo line2 >> foo $ hg ci -m '1: change foo' $ hg up -C 0 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg mv foo bar $ rm bar $ echo line0 > bar $ echo line1 >> bar $ hg ci -m '2: mv foo bar; change bar' created new head $ hg merge 1 merging bar and foo to bar 0 files updated, 1 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ cat bar line0 line1 line2 $ hg ci -m '3: merge with local rename' $ hg debugindex bar rev linkrev nodeid p1 p2 0 2 d35118874825 000000000000 000000000000 1 3 5345f5ab8abd 000000000000 d35118874825 $ hg debugrename bar bar renamed from foo:9e25c27b87571a1edee5ae4dddee5687746cc8e2 $ hg debugindex foo rev linkrev nodeid p1 p2 0 0 690b295714ae 000000000000 000000000000 1 1 9e25c27b8757 690b295714ae 000000000000 Revert the content change from rev 2: $ hg up -C 2 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ rm bar $ echo line1 > bar $ hg ci -m '4: revert content change from rev 2' created new head $ hg log --template '{rev}:{node|short} {parents}\n' 4:2263c1be0967 2:0f2ff26688b9 3:0555950ead28 2:0f2ff26688b9 1:5cd961e4045d 2:0f2ff26688b9 0:2665aaee66e9 1:5cd961e4045d 0:2665aaee66e9 This should use bar@rev2 as the ancestor: $ hg --debug merge 3 searching for copies back to rev 1 resolving manifests branchmerge: True, force: False, partial: False ancestor: 0f2ff26688b9, local: 2263c1be0967+, remote: 0555950ead28 preserving bar for resolve of bar starting 4 threads for background file closing (?) bar: versions differ -> m (premerge) picked tool ':merge' for bar (binary False symlink False changedelete False) merging bar my bar@2263c1be0967+ other bar@0555950ead28 ancestor bar@0f2ff26688b9 premerge successful 0 files updated, 1 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ cat bar line1 line2 $ hg ci -m '5: merge' $ hg debugindex bar rev linkrev nodeid p1 p2 0 2 d35118874825 000000000000 000000000000 1 3 5345f5ab8abd 000000000000 d35118874825 2 4 ff4b45017382 d35118874825 000000000000 3 5 3701b4893544 ff4b45017382 5345f5ab8abd Same thing, but with the merge on 3 having the rename on the remote parent: $ cd .. $ hg clone -U -r 1 -r 2 a b adding changesets adding manifests adding file changes added 3 changesets with 3 changes to 2 files (+1 heads) new changesets 2665aaee66e9:0f2ff26688b9 $ cd b $ hg up -C 1 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg merge 2 merging foo and bar to bar 0 files updated, 1 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ cat bar line0 line1 line2 $ hg ci -m '3: merge with remote rename' $ hg debugindex bar rev linkrev nodeid p1 p2 0 2 d35118874825 000000000000 000000000000 1 3 5345f5ab8abd 000000000000 d35118874825 $ hg debugrename bar bar renamed from foo:9e25c27b87571a1edee5ae4dddee5687746cc8e2 $ hg debugindex foo rev linkrev nodeid p1 p2 0 0 690b295714ae 000000000000 000000000000 1 1 9e25c27b8757 690b295714ae 000000000000 Revert the content change from rev 2: $ hg up -C 2 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ rm bar $ echo line1 > bar $ hg ci -m '4: revert content change from rev 2' created new head $ hg log --template '{rev}:{node|short} {parents}\n' 4:2263c1be0967 2:0f2ff26688b9 3:3ffa6b9e35f0 1:5cd961e4045d 2:0f2ff26688b9 2:0f2ff26688b9 0:2665aaee66e9 1:5cd961e4045d 0:2665aaee66e9 This should use bar@rev2 as the ancestor: $ hg --debug merge 3 searching for copies back to rev 1 resolving manifests branchmerge: True, force: False, partial: False ancestor: 0f2ff26688b9, local: 2263c1be0967+, remote: 3ffa6b9e35f0 preserving bar for resolve of bar starting 4 threads for background file closing (?) bar: versions differ -> m (premerge) picked tool ':merge' for bar (binary False symlink False changedelete False) merging bar my bar@2263c1be0967+ other bar@3ffa6b9e35f0 ancestor bar@0f2ff26688b9 premerge successful 0 files updated, 1 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ cat bar line1 line2 $ hg ci -m '5: merge' $ hg debugindex bar rev linkrev nodeid p1 p2 0 2 d35118874825 000000000000 000000000000 1 3 5345f5ab8abd 000000000000 d35118874825 2 4 ff4b45017382 d35118874825 000000000000 3 5 3701b4893544 ff4b45017382 5345f5ab8abd $ cd ..