Mercurial > hg
view mercurial/scmwindows.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 | e24802ea8dbd |
children | 57875cf423c9 |
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from __future__ import absolute_import import os from . import ( encoding, pycompat, util, win32, ) try: import _winreg as winreg winreg.CloseKey except ImportError: import winreg # MS-DOS 'more' is the only pager available by default on Windows. fallbackpager = 'more' def systemrcpath(): '''return default os-specific hgrc search path''' rcpath = [] filename = win32.executablepath() # Use mercurial.ini found in directory with hg.exe progrc = os.path.join(os.path.dirname(filename), 'mercurial.ini') rcpath.append(progrc) # Use hgrc.d found in directory with hg.exe progrcd = os.path.join(os.path.dirname(filename), 'hgrc.d') if os.path.isdir(progrcd): for f, kind in util.listdir(progrcd): if f.endswith('.rc'): rcpath.append(os.path.join(progrcd, f)) # else look for a system rcpath in the registry value = util.lookupreg('SOFTWARE\\Mercurial', None, winreg.HKEY_LOCAL_MACHINE) if not isinstance(value, str) or not value: return rcpath value = util.localpath(value) for p in value.split(pycompat.ospathsep): if p.lower().endswith('mercurial.ini'): rcpath.append(p) elif os.path.isdir(p): for f, kind in util.listdir(p): if f.endswith('.rc'): rcpath.append(os.path.join(p, f)) return rcpath def userrcpath(): '''return os-specific hgrc search path to the user dir''' home = os.path.expanduser('~') path = [os.path.join(home, 'mercurial.ini'), os.path.join(home, '.hgrc')] userprofile = encoding.environ.get('USERPROFILE') if userprofile and userprofile != home: path.append(os.path.join(userprofile, 'mercurial.ini')) path.append(os.path.join(userprofile, '.hgrc')) return path def termsize(ui): return win32.termsize()