Mercurial > hg
view tests/test-drawdag.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 |
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$ cat >> $HGRCPATH<<EOF > [extensions] > drawdag=$TESTDIR/drawdag.py > [experimental] > evolution=true > EOF $ reinit () { > rm -rf .hg && hg init > } $ hg init Test what said in drawdag.py docstring $ hg debugdrawdag <<'EOS' > c d > |/ > b > | > a > EOS $ hg log -G -T '{rev} {desc} ({tags})' o 3 d (d tip) | | o 2 c (c) |/ o 1 b (b) | o 0 a (a) $ hg debugdrawdag <<'EOS' > foo bar bar foo > | / | | > ancestor(c,d) a baz > EOS $ hg log -G -T '{desc}' o foo |\ +---o bar | | | | o | baz | / +---o d | | +---o c | | o | b |/ o a $ reinit $ hg debugdrawdag <<'EOS' > o foo > |\ > +---o bar > | | | > | o | baz > | / > +---o d > | | > +---o c > | | > o | b > |/ > o a > EOS $ hg log -G -T '{desc}' o foo |\ | | o d | |/ | | o c | |/ | | o bar | |/| | o | b | |/ o / baz / o a $ reinit $ hg debugdrawdag <<'EOS' > o foo > |\ > | | o d > | |/ > | | o c > | |/ > | | o bar > | |/| > | o | b > | |/ > o / baz > / > o a > EOS $ hg log -G -T '{desc}' o foo |\ | | o d | |/ | | o c | |/ | | o bar | |/| | o | b | |/ o / baz / o a $ hg manifest -r a a $ hg manifest -r b a b $ hg manifest -r bar a b $ hg manifest -r foo a b baz Edges existed in repo are no-ops $ reinit $ hg debugdrawdag <<'EOS' > B C C > | | | > A A B > EOS $ hg log -G -T '{desc}' o C |\ | o B |/ o A $ hg debugdrawdag <<'EOS' > C D C > | | | > B B A > EOS $ hg log -G -T '{desc}' o D | | o C |/| o | B |/ o A Node with more than 2 parents are disallowed $ hg debugdrawdag <<'EOS' > A > /|\ > D B C > EOS abort: A: too many parents: C D B [255] Cycles are disallowed $ hg debugdrawdag <<'EOS' > A > | > A > EOS abort: the graph has cycles [255] $ hg debugdrawdag <<'EOS' > A > | > B > | > A > EOS abort: the graph has cycles [255] Create obsmarkers via comments $ reinit $ hg debugdrawdag <<'EOS' > G > | > I D C F # split: B -> E, F, G > \ \| | # replace: C -> D -> H > H B E # prune: F, I > \|/ > A > EOS 1 new orphan changesets $ hg log -r 'sort(all(), topo)' -G --hidden -T '{desc} {node}' * G 711f53bbef0bebd12eb6f0511d5e2e998b984846 | x F 64a8289d249234b9886244d379f15e6b650b28e3 | o E 7fb047a69f220c21711122dfd94305a9efb60cba | | x D be0ef73c17ade3fc89dc41701eb9fc3a91b58282 | | | | x C 26805aba1e600a82e93661149f2313866a221a7b | |/ | x B 112478962961147124edd43549aedd1a335e44bf |/ | x I 58e6b987bf7045fcd9c54f496396ca1d1fc81047 | | | o H 575c4b5ec114d64b681d33f8792853568bfb2b2c |/ o A 426bada5c67598ca65036d57d9e4b64b0c1ce7a0 $ hg debugobsolete 112478962961147124edd43549aedd1a335e44bf 7fb047a69f220c21711122dfd94305a9efb60cba 64a8289d249234b9886244d379f15e6b650b28e3 711f53bbef0bebd12eb6f0511d5e2e998b984846 0 (Thu Jan 01 00:00:00 1970 +0000) {'ef1': '0', 'operation': 'split', 'user': 'test'} 26805aba1e600a82e93661149f2313866a221a7b be0ef73c17ade3fc89dc41701eb9fc3a91b58282 0 (Thu Jan 01 00:00:00 1970 +0000) {'ef1': '9', 'operation': 'replace', 'user': 'test'} be0ef73c17ade3fc89dc41701eb9fc3a91b58282 575c4b5ec114d64b681d33f8792853568bfb2b2c 0 (Thu Jan 01 00:00:00 1970 +0000) {'ef1': '13', 'operation': 'replace', 'user': 'test'} 64a8289d249234b9886244d379f15e6b650b28e3 0 {7fb047a69f220c21711122dfd94305a9efb60cba} (Thu Jan 01 00:00:00 1970 +0000) {'ef1': '0', 'operation': 'prune', 'user': 'test'} 58e6b987bf7045fcd9c54f496396ca1d1fc81047 0 {575c4b5ec114d64b681d33f8792853568bfb2b2c} (Thu Jan 01 00:00:00 1970 +0000) {'ef1': '0', 'operation': 'prune', 'user': 'test'} Change file contents via comments $ reinit $ hg debugdrawdag <<'EOS' > C # A/dir1/a = 1\n2 > |\ # B/dir2/b = 34 > A B # C/dir1/c = 5 > # C/dir2/c = 6 > # C/A = a > # C/B = b > EOS $ hg log -G -T '{desc} {files}' o C A B dir1/c dir2/c |\ | o B B dir2/b | o A A dir1/a $ for f in `hg files -r C`; do > echo FILE "$f" > hg cat -r C "$f" > echo > done FILE A a FILE B b FILE dir1/a 1 2 FILE dir1/c 5 FILE dir2/b 34 FILE dir2/c 6