Mercurial > hg
view tests/test-convert-cvs-synthetic.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 | 96529f81e2e9 |
children | e5e5ee2b60e4 |
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#require cvs112 This feature requires use of builtin cvsps! $ echo "[extensions]" >> $HGRCPATH $ echo "convert = " >> $HGRCPATH create cvs repository with one project $ mkdir cvsrepo $ cd cvsrepo $ CVSROOT=`pwd` $ export CVSROOT $ CVS_OPTIONS=-f $ export CVS_OPTIONS $ cd .. $ rmdir cvsrepo $ cvscall() > { > cvs -f "$@" > } output of 'cvs ci' varies unpredictably, so just discard it $ cvsci() > { > sleep 1 > cvs -f ci "$@" >/dev/null > } $ cvscall -d "$CVSROOT" init $ mkdir cvsrepo/proj $ cvscall -q co proj create file1 on the trunk $ cd proj $ touch file1 $ cvscall -Q add file1 $ cvsci -m"add file1 on trunk" file1 create two branches $ cvscall -q tag -b v1_0 T file1 $ cvscall -q tag -b v1_1 T file1 create file2 on branch v1_0 $ cvscall -Q up -rv1_0 $ touch file2 $ cvscall -Q add file2 $ cvsci -m"add file2" file2 create file3, file4 on branch v1_1 $ cvscall -Q up -rv1_1 $ touch file3 $ touch file4 $ cvscall -Q add file3 file4 $ cvsci -m"add file3, file4 on branch v1_1" file3 file4 merge file2 from v1_0 to v1_1 $ cvscall -Q up -jv1_0 $ cvsci -m"MERGE from v1_0: add file2" cvs commit: Examining . Step things up a notch: now we make the history really hairy, with changes bouncing back and forth between trunk and v1_2 and merges going both ways. (I.e., try to model the real world.) create branch v1_2 $ cvscall -Q up -A $ cvscall -q tag -b v1_2 T file1 create file5 on branch v1_2 $ cvscall -Q up -rv1_2 $ touch file5 $ cvs -Q add file5 $ cvsci -m"add file5 on v1_2" cvs commit: Examining . create file6 on trunk post-v1_2 $ cvscall -Q up -A $ touch file6 $ cvscall -Q add file6 $ cvsci -m"add file6 on trunk post-v1_2" cvs commit: Examining . merge file5 from v1_2 to trunk $ cvscall -Q up -A $ cvscall -Q up -jv1_2 file5 $ cvsci -m"MERGE from v1_2: add file5" cvs commit: Examining . merge file6 from trunk to v1_2 $ cvscall -Q up -rv1_2 $ cvscall up -jHEAD file6 U file6 $ cvsci -m"MERGE from HEAD: add file6" cvs commit: Examining . cvs rlog output $ cvscall -q rlog proj | egrep '^(RCS file|revision)' RCS file: $TESTTMP/cvsrepo/proj/file1,v revision 1.1 RCS file: $TESTTMP/cvsrepo/proj/Attic/file2,v revision 1.1 revision 1.1.4.2 revision 1.1.4.1 revision 1.1.2.1 RCS file: $TESTTMP/cvsrepo/proj/Attic/file3,v revision 1.1 revision 1.1.2.1 RCS file: $TESTTMP/cvsrepo/proj/Attic/file4,v revision 1.1 revision 1.1.2.1 RCS file: $TESTTMP/cvsrepo/proj/file5,v revision 1.2 revision 1.1 revision 1.1.2.1 RCS file: $TESTTMP/cvsrepo/proj/file6,v revision 1.1 revision 1.1.2.2 revision 1.1.2.1 convert to hg (#1) $ cd .. $ hg convert --datesort proj proj.hg initializing destination proj.hg repository connecting to $TESTTMP/cvsrepo scanning source... collecting CVS rlog 15 log entries creating changesets 9 changeset entries sorting... converting... 8 add file1 on trunk 7 add file2 6 MERGE from v1_0: add file2 5 file file3 was initially added on branch v1_1. 4 add file3, file4 on branch v1_1 3 add file5 on v1_2 2 add file6 on trunk post-v1_2 1 MERGE from HEAD: add file6 0 MERGE from v1_2: add file5 hg log -G output (#1) $ hg -R proj.hg log -G --template "{rev} {desc}\n" o 8 MERGE from v1_2: add file5 | | o 7 MERGE from HEAD: add file6 | | o | 6 add file6 on trunk post-v1_2 | | | o 5 add file5 on v1_2 | | | | o 4 add file3, file4 on branch v1_1 | | | o | | 3 file file3 was initially added on branch v1_1. |/ / | o 2 MERGE from v1_0: add file2 |/ | o 1 add file2 |/ o 0 add file1 on trunk convert to hg (#2: with merge detection) $ hg convert \ > --config convert.cvsps.mergefrom='"^MERGE from (\S+):"' \ > --datesort \ > proj proj.hg2 initializing destination proj.hg2 repository connecting to $TESTTMP/cvsrepo scanning source... collecting CVS rlog 15 log entries creating changesets 9 changeset entries sorting... converting... 8 add file1 on trunk 7 add file2 6 MERGE from v1_0: add file2 5 file file3 was initially added on branch v1_1. 4 add file3, file4 on branch v1_1 3 add file5 on v1_2 2 add file6 on trunk post-v1_2 1 MERGE from HEAD: add file6 0 MERGE from v1_2: add file5 hg log -G output (#2) $ hg -R proj.hg2 log -G --template "{rev} {desc}\n" o 8 MERGE from v1_2: add file5 | | o 7 MERGE from HEAD: add file6 | | o | 6 add file6 on trunk post-v1_2 | | | o 5 add file5 on v1_2 | | | | o 4 add file3, file4 on branch v1_1 | | | o | | 3 file file3 was initially added on branch v1_1. |/ / | o 2 MERGE from v1_0: add file2 |/ | o 1 add file2 |/ o 0 add file1 on trunk