Mercurial > hg
view tests/test-exchange-obsmarkers-case-B4.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 | 4a4fa665e1b4 |
children |
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============================================ Testing obsolescence markers push: Cases B.4 ============================================ Mercurial pushes obsolescences markers relevant to the "pushed-set", the set of all changesets that requested to be "in sync" after the push (even if they are already on both side). This test belongs to a series of tests checking such set is properly computed and applied. This does not tests "obsmarkers" discovery capabilities. Category B: pruning case TestCase 4: Pruned changeset on common part of the history Variants: # a: explicite push # b: bare push B.4 Pruned changeset on common part of history ============================================= .. {{{ .. ⊗ C .. | ● B .. | | .. | ● A .. |/ .. ● O .. }}} .. .. Marker exist from: .. .. * C (prune) .. .. Command run: .. .. * hg push -r B .. * hg push .. .. Expected exchange: .. .. * prune for C Setup ----- $ . $TESTDIR/testlib/exchange-obsmarker-util.sh initial $ setuprepos B.4 creating test repo for test case B.4 - pulldest - main - pushdest cd into `main` and proceed with env setup $ cd main $ mkcommit A $ mkcommit B $ hg phase --public . $ hg push ../pushdest pushing to ../pushdest searching for changes remote: adding changesets remote: adding manifests remote: adding file changes remote: added 2 changesets with 2 changes to 2 files $ hg push ../pulldest pushing to ../pulldest searching for changes remote: adding changesets remote: adding manifests remote: adding file changes remote: added 2 changesets with 2 changes to 2 files $ hg update -q 0 $ mkcommit C created new head $ hg prune -qd '0 0' . $ hg log -G --hidden x 7f7f229b13a6 (draft): C | | o f6fbb35d8ac9 (public): B | | | o f5bc6836db60 (public): A |/ @ a9bdc8b26820 (public): O $ inspect_obsmarkers obsstore content ================ 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} $ cd .. $ cd .. $ cp -R B.4 B.4.a $ cp -R B.4 B.4.b Actual Test (explicit push version) ----------------------------------- $ dotest B.4.a O ## Running testcase B.4.a # testing echange of "O" (a9bdc8b26820) ## initial state # obstore: main 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pushdest # obstore: pulldest ## pushing "O" from main to pushdest pushing to pushdest searching for changes no changes found remote: 1 new obsolescence markers ## post push state # obstore: main 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pushdest 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pulldest ## pulling "a9bdc8b26820" from main into pulldest pulling from main no changes found 1 new obsolescence markers ## post pull state # obstore: main 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pushdest 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pulldest 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} Actual Test (bare push version) ----------------------------------- $ dotest B.4.b ## Running testcase B.4.b ## initial state # obstore: main 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pushdest # obstore: pulldest ## pushing from main to pushdest pushing to pushdest searching for changes no changes found remote: 1 new obsolescence markers ## post push state # obstore: main 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pushdest 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pulldest ## pulling from main into pulldest pulling from main searching for changes no changes found 1 new obsolescence markers ## post pull state # obstore: main 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pushdest 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pulldest 7f7f229b13a629a5b20581c6cb723f4e2ca54bed 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}