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view tests/svnxml.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 | 812eb3b7dc43 |
children | c17d73bf6a4d |
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# Read the output of a "svn log --xml" command on stdin, parse it and # print a subset of attributes common to all svn versions tested by # hg. from __future__ import absolute_import import sys import xml.dom.minidom def xmltext(e): return ''.join(c.data for c in e.childNodes if c.nodeType == c.TEXT_NODE) def parseentry(entry): e = {} e['revision'] = entry.getAttribute('revision') e['author'] = xmltext(entry.getElementsByTagName('author')[0]) e['msg'] = xmltext(entry.getElementsByTagName('msg')[0]) e['paths'] = [] paths = entry.getElementsByTagName('paths') if paths: paths = paths[0] for p in paths.getElementsByTagName('path'): action = p.getAttribute('action') path = xmltext(p) frompath = p.getAttribute('copyfrom-path') fromrev = p.getAttribute('copyfrom-rev') e['paths'].append((path, action, frompath, fromrev)) return e def parselog(data): entries = [] doc = xml.dom.minidom.parseString(data) for e in doc.getElementsByTagName('logentry'): entries.append(parseentry(e)) return entries def printentries(entries): fp = sys.stdout for e in entries: for k in ('revision', 'author', 'msg'): fp.write(('%s: %s\n' % (k, e[k])).encode('utf-8')) for path, action, fpath, frev in sorted(e['paths']): frominfo = '' if frev: frominfo = ' (from %s@%s)' % (fpath, frev) p = ' %s %s%s\n' % (action, path, frominfo) fp.write(p.encode('utf-8')) if __name__ == '__main__': data = sys.stdin.read() entries = parselog(data) printentries(entries)