Mercurial > hg
view contrib/dirstatenonnormalcheck.py @ 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 | 6e7fae8f1c6c |
children | 2372284d9457 |
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# dirstatenonnormalcheck.py - extension to check the consistency of the # dirstate's non-normal map # # For most operations on dirstate, this extensions checks that the nonnormalset # contains the right entries. # It compares the nonnormal file to a nonnormalset built from the map of all # the files in the dirstate to check that they contain the same files. from __future__ import absolute_import from mercurial import ( dirstate, extensions, ) def nonnormalentries(dmap): """Compute nonnormal entries from dirstate's dmap""" res = set() for f, e in dmap.iteritems(): if e[0] != b'n' or e[3] == -1: res.add(f) return res def checkconsistency(ui, orig, dmap, _nonnormalset, label): """Compute nonnormalset from dmap, check that it matches _nonnormalset""" nonnormalcomputedmap = nonnormalentries(dmap) if _nonnormalset != nonnormalcomputedmap: ui.develwarn(b"%s call to %s\n" % (label, orig), config=b'dirstate') ui.develwarn(b"inconsistency in nonnormalset\n", config=b'dirstate') ui.develwarn(b"[nonnormalset] %s\n" % _nonnormalset, config=b'dirstate') ui.develwarn(b"[map] %s\n" % nonnormalcomputedmap, config=b'dirstate') def _checkdirstate(orig, self, arg): """Check nonnormal set consistency before and after the call to orig""" checkconsistency(self._ui, orig, self._map, self._map.nonnormalset, b"before") r = orig(self, arg) checkconsistency(self._ui, orig, self._map, self._map.nonnormalset, b"after") return r def extsetup(ui): """Wrap functions modifying dirstate to check nonnormalset consistency""" dirstatecl = dirstate.dirstate devel = ui.configbool(b'devel', b'all-warnings') paranoid = ui.configbool(b'experimental', b'nonnormalparanoidcheck') if devel: extensions.wrapfunction(dirstatecl, '_writedirstate', _checkdirstate) if paranoid: # We don't do all these checks when paranoid is disable as it would # make the extension run very slowly on large repos extensions.wrapfunction(dirstatecl, 'normallookup', _checkdirstate) extensions.wrapfunction(dirstatecl, 'otherparent', _checkdirstate) extensions.wrapfunction(dirstatecl, 'normal', _checkdirstate) extensions.wrapfunction(dirstatecl, 'write', _checkdirstate) extensions.wrapfunction(dirstatecl, 'add', _checkdirstate) extensions.wrapfunction(dirstatecl, 'remove', _checkdirstate) extensions.wrapfunction(dirstatecl, 'merge', _checkdirstate) extensions.wrapfunction(dirstatecl, 'drop', _checkdirstate)