streamclone: use backgroundfilecloser (issue4889)
Closing files that have been appended to is slow on Windows/NTFS.
CloseHandle() calls on this platform often take 1-10ms - and that's
on my i7-6700K Skylake processor with a modern and fast SSD. Contrast
with other I/O operations, such as writing data, which take <100us.
This means that creating/appending thousands of files can add
significant overhead. For example, cloning mozilla-central creates
~232,000 revlog files. Assuming 1ms per CloseHandle(), that yields
232s (3:52) of wall time waiting for file closes!
The impact of this overhead can be measured most directly when applying
stream clone bundles. Applying these files is effectively uncompressing
a tar archive (read: it's very fast).
Using a RAM disk (read: no I/O wait), the difference in wall time for a
`hg debugapplystreamclonebundle` for a ~1731 MB mozilla-central bundle
between Windows and Linux from the same machine is drastic:
Linux: ~12.8s (128MB/s)
Windows: ~352.0s (4.7MB/s)
Windows is ~27.5x slower. Yikes!
After this patch:
Linux: ~12.8s (128MB/s)
Windows: ~102.1s (16.1MB/s)
Windows is now ~3.4x faster. Unfortunately, it is still ~8x slower than
Linux. Profiling reveals a few hot code paths that could likely be
improved. But those are for other patches.
This patch introduces test-clone-uncompressed.t because existing tests
of `clone --uncompressed` are scattered about and adding a variation for
background thread closing to e.g. test-http.t doesn't feel correct.
# this is hack to make sure no escape characters are inserted into the output
import os, sys
if 'TERM' in os.environ:
del os.environ['TERM']
import doctest
def testmod(name, optionflags=0, testtarget=None):
__import__(name)
mod = sys.modules[name]
if testtarget is not None:
mod = getattr(mod, testtarget)
doctest.testmod(mod, optionflags=optionflags)
testmod('mercurial.changegroup')
testmod('mercurial.changelog')
testmod('mercurial.dagparser', optionflags=doctest.NORMALIZE_WHITESPACE)
testmod('mercurial.dispatch')
testmod('mercurial.encoding')
testmod('mercurial.hg')
testmod('mercurial.hgweb.hgwebdir_mod')
testmod('mercurial.match')
testmod('mercurial.minirst')
testmod('mercurial.patch')
testmod('mercurial.pathutil')
testmod('mercurial.parser')
testmod('mercurial.revset')
testmod('mercurial.store')
testmod('mercurial.subrepo')
testmod('mercurial.templatefilters')
testmod('mercurial.templater')
testmod('mercurial.ui')
testmod('mercurial.url')
testmod('mercurial.util')
testmod('mercurial.util', testtarget='platform')
testmod('hgext.convert.convcmd')
testmod('hgext.convert.cvsps')
testmod('hgext.convert.filemap')
testmod('hgext.convert.p4')
testmod('hgext.convert.subversion')
testmod('hgext.mq')