Mercurial > hg
view tests/check-perf-code.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> |
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date | Wed, 18 Jul 2018 09:49:34 -0700 |
parents | bd872f64a8ba |
children | eb8a8af4cbd0 |
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#!/usr/bin/env python # # check-perf-code - (historical) portability checker for contrib/perf.py from __future__ import absolute_import import os import sys # write static check patterns here perfpypats = [ [ (r'(branchmap|repoview)\.subsettable', "use getbranchmapsubsettable() for early Mercurial"), (r'\.(vfs|svfs|opener|sopener)', "use getvfs()/getsvfs() for early Mercurial"), (r'ui\.configint', "use getint() instead of ui.configint() for early Mercurial"), ], # warnings [ ] ] def modulewhitelist(names): replacement = [('.py', ''), ('.c', ''), # trim suffix ('mercurial%s' % (os.sep), ''), # trim "mercurial/" path ] ignored = {'__init__'} modules = {} # convert from file name to module name, and count # of appearances for name in names: name = name.strip() for old, new in replacement: name = name.replace(old, new) if name not in ignored: modules[name] = modules.get(name, 0) + 1 # list up module names, which appear multiple times whitelist = [] for name, count in modules.items(): if count > 1: whitelist.append(name) return whitelist if __name__ == "__main__": # in this case, it is assumed that result of "hg files" at # multiple revisions is given via stdin whitelist = modulewhitelist(sys.stdin) assert whitelist, "module whitelist is empty" # build up module whitelist check from file names given at runtime perfpypats[0].append( # this matching pattern assumes importing modules from # "mercurial" package in the current style below, for simplicity # # from mercurial import ( # foo, # bar, # baz # ) ((r'from mercurial import [(][a-z0-9, \n#]*\n(?! *%s,|^[ #]*\n|[)])' % ',| *'.join(whitelist)), "import newer module separately in try clause for early Mercurial" )) # import contrib/check-code.py as checkcode assert 'RUNTESTDIR' in os.environ, "use check-perf-code.py in *.t script" contribpath = os.path.join(os.environ['RUNTESTDIR'], '..', 'contrib') sys.path.insert(0, contribpath) checkcode = __import__('check-code') # register perf.py specific entry with "checks" in check-code.py checkcode.checks.append(('perf.py', r'contrib/perf.py$', '', checkcode.pyfilters, perfpypats)) sys.exit(checkcode.main())