Mercurial > hg
view tests/test-exchange-obsmarkers-case-A4.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 | 1a09dad8b85a |
children | 89630d0b3e23 |
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============================================ Testing obsolescence markers push: Cases A.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 A: simple cases Testcase 4: Push in the middle of the obsolescence chain A.4 Push in the middle of the obsolescence chain ================================================ .. (Where we show that we should not push the marker without the successors) .. .. {{{ .. B ◔ .. | .. A⇠ø⇠○ A' .. |/ .. ● O .. }}} .. .. Markers exist from: .. .. * `A ø⇠○ A'` .. * chain from A .. .. Command runs: .. .. * hg push -r B .. .. Expected exchange: .. .. * Chain from A .. .. Expected Exclude: .. .. * `Ai ø⇠○ A'` Setup ----- $ . $TESTDIR/testlib/exchange-obsmarker-util.sh initial $ setuprepos A.4 creating test repo for test case A.4 - pulldest - main - pushdest cd into `main` and proceed with env setup $ cd main $ mkcommit A0 $ mkcommit B $ hg update 0 0 files updated, 0 files merged, 2 files removed, 0 files unresolved $ mkcommit A1 created new head $ hg debugobsolete aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa `getid 'desc(A0)'` $ hg debugobsolete `getid 'desc(A0)'` `getid 'desc(A1)'` obsoleted 1 changesets 1 new orphan changesets $ hg log -G --hidden @ e5ea8f9c7314 (draft): A1 | | * 06055a7959d4 (draft): B | | | x 28b51eb45704 (draft): A0 |/ o a9bdc8b26820 (public): O $ inspect_obsmarkers obsstore content ================ aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 28b51eb45704506b5c603decd6bf7ac5e0f6a52f 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} $ cd .. $ cd .. Actual Test for first version ----------------------------- $ dotest A.4 B -f ## Running testcase A.4 # testing echange of "B" (06055a7959d4) ## initial state # obstore: main 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 28b51eb45704506b5c603decd6bf7ac5e0f6a52f 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pushdest # obstore: pulldest ## pushing "B" from main to 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 remote: 1 new obsolescence markers ## post push state # obstore: main 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 28b51eb45704506b5c603decd6bf7ac5e0f6a52f 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pushdest aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 28b51eb45704506b5c603decd6bf7ac5e0f6a52f 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pulldest ## pulling "06055a7959d4" from main into pulldest pulling from main searching for changes adding changesets adding manifests adding file changes added 2 changesets with 2 changes to 2 files 1 new obsolescence markers new changesets 28b51eb45704:06055a7959d4 (run 'hg update' to get a working copy) ## post pull state # obstore: main 28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 28b51eb45704506b5c603decd6bf7ac5e0f6a52f 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pushdest aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 28b51eb45704506b5c603decd6bf7ac5e0f6a52f 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'} # obstore: pulldest aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa 28b51eb45704506b5c603decd6bf7ac5e0f6a52f 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}