Mercurial > hg
view mercurial/scmposix.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 | dacfcdd8b94e |
children | 57875cf423c9 |
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from __future__ import absolute_import import array import errno import fcntl import os import sys from . import ( encoding, pycompat, util, ) # BSD 'more' escapes ANSI color sequences by default. This can be disabled by # $MORE variable, but there's no compatible option with Linux 'more'. Given # OS X is widely used and most modern Unix systems would have 'less', setting # 'less' as the default seems reasonable. fallbackpager = 'less' def _rcfiles(path): rcs = [os.path.join(path, 'hgrc')] rcdir = os.path.join(path, 'hgrc.d') try: rcs.extend([os.path.join(rcdir, f) for f, kind in util.listdir(rcdir) if f.endswith(".rc")]) except OSError: pass return rcs def systemrcpath(): path = [] if pycompat.sysplatform == 'plan9': root = 'lib/mercurial' else: root = 'etc/mercurial' # old mod_python does not set sys.argv if len(getattr(sys, 'argv', [])) > 0: p = os.path.dirname(os.path.dirname(pycompat.sysargv[0])) if p != '/': path.extend(_rcfiles(os.path.join(p, root))) path.extend(_rcfiles('/' + root)) return path def userrcpath(): if pycompat.sysplatform == 'plan9': return [encoding.environ['home'] + '/lib/hgrc'] elif pycompat.isdarwin: return [os.path.expanduser('~/.hgrc')] else: confighome = encoding.environ.get('XDG_CONFIG_HOME') if confighome is None or not os.path.isabs(confighome): confighome = os.path.expanduser('~/.config') return [os.path.expanduser('~/.hgrc'), os.path.join(confighome, 'hg', 'hgrc')] def termsize(ui): try: import termios TIOCGWINSZ = termios.TIOCGWINSZ # unavailable on IRIX (issue3449) except (AttributeError, ImportError): return 80, 24 for dev in (ui.ferr, ui.fout, ui.fin): try: try: fd = dev.fileno() except AttributeError: continue if not os.isatty(fd): continue arri = fcntl.ioctl(fd, TIOCGWINSZ, '\0' * 8) height, width = array.array(r'h', arri)[:2] if width > 0 and height > 0: return width, height except ValueError: pass except IOError as e: if e[0] == errno.EINVAL: pass else: raise return 80, 24