upstream/mercurial-mirror Files · mercurial/scmposix.py

snapshot: search for unrelated but reusable full-snapshot...

snapshot: search for unrelated but reusable full-snapshot # New Strategy Step: Reusing Snapshot Outside Of Parents' Chain. If no suitable bases were found in the parent's chains, see if we could reuse a full snapshot not directly related to the current revision. Such search can be expensive, so we only search for snapshots appended to the revlog *after* the bases used by the parents of the current revision (the one we just tested). We assume the parent's bases were created because the previous snapshots were unsuitable, so there are low odds they would be useful now. This search gives a chance to reuse a delta chain unrelated to the current revision. Without this re-use, topological branches would keep reopening new full chains. Creating more and more snapshots as the repository grow. In repositories with many topological branches, the lack of delta reuse can create too many snapshots reducing overall compression to nothing. This results in a very large repository and other usability issues. For now, we still focus on creating level-1 snapshots. However, this principle will play a large part in how we avoid snapshot explosion once we have more snapshot levels. # Effects On The Test Repository In the test repository we created, we can see the beneficial effect of such reuse. We need very few level-0 snapshots and the overall revlog size has decreased. The `hg debugrevlog` call, show a "lvl-2" snapshot. It comes from the existing delta logic using the `prev` revision (revlog's tip) as the base. In this specific case, it turns out the tip was a level-1 snapshot. This is a coincidence that can be ignored. Finding and testing against all these unrelated snapshots can have a performance impact at write time. We currently focus on building good deltas chain we build. Performance concern will be dealt with later in another series.

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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

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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