view mercurial/dagparser.py @ 42043:1fac9b931d46

compression: introduce a `storage.revlog.zlib.level` configuration

This option control the zlib compression level used when compression revlog
chunk.

This is also a good excuse to pave the way for a similar configuration option
for the zstd compression engine. Having a dedicated option for each compression
algorithm is useful because they don't support the same range of values.

Using a higher zlib compression impact CPU consumption at compression time, but
does not directly affected decompression time. However dealing with small
compressed chunk can directly help decompression and indirectly help other
revlog logic.

I ran some basic test on repositories using different level. I am using the
mercurial, pypy, netbeans and mozilla-central clone from our benchmark suite.
All tested repository use sparse-revlog and got all their delta recomputed.

The different compression level has a small effect on the repository size
(about 10% variation in the total range). My quick analysis is that revlog
mostly store small delta, that are not affected by the compression level much.
So the variation probably mostly comes from better compression of the snapshots
revisions, and snapshot revision only represent a small portion of the
repository content.

I also made some basic timings measurements. The "read" timings are gathered using
simple run of `hg perfrevlogrevisions`, the "write" timings using `hg
perfrevlogwrite` (restricted to the last 5000 revisions for netbeans and
mozilla central). The timings are gathered on a generic machine, (not one  of
our performance locked machine), so small variation might not be meaningful.
However large trend remains relevant.

Keep in mind that these numbers are not pure compression/decompression time.
They also involve the full revlog logic. In particular the difference in chunk
size has an impact on the delta chain structure, affecting performance when
writing or reading them.

On read/write performance, the compression level has a bigger impact.
Counter-intuitively, the higher compression levels improve "write" performance
for the large repositories in our tested setting. Maybe because the last 5000
delta chain end up having a very different shape in this specific spot? Or maybe
because of a more general trend of better delta chains thanks to the smaller
chunk and snapshot.

This series does not intend to change the default compression level. However,
these result call for a deeper analysis of this performance difference in the
future.

Full data
=========

repo   level  .hg/store size  00manifest.d read       write
----------------------------------------------------------------
mercurial  1      49,402,813     5,963,475   0.170159  53.250304
mercurial  6      47,197,397     5,875,730   0.182820  56.264320
mercurial  9      47,121,596     5,849,781   0.189219  56.293612

pypy       1     370,830,572    28,462,425   2.679217 460.721984
pypy       6     340,112,317    27,648,747   2.768691 467.537158
pypy       9     338,360,736    27,639,003   2.763495 476.589918

netbeans   1   1,281,847,810   165,495,457 122.477027 520.560316
netbeans   6   1,205,284,353   159,161,207 139.876147 715.930400
netbeans   9   1,197,135,671   155,034,586 141.620281 678.297064

mozilla    1   2,775,497,186   298,527,987 147.867662 751.263721
mozilla    6   2,596,856,420   286,597,671 170.572118 987.056093
mozilla    9   2,587,542,494   287,018,264 163.622338 739.803002

# dagparser.py - parser and generator for concise description of DAGs
#
# Copyright 2010 Peter Arrenbrecht <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import re
import string

from .i18n import _
from . import (
    error,
    pycompat,
)
from .utils import (
    stringutil,
)

def parsedag(desc):
    '''parses a DAG from a concise textual description; generates events

    "+n" is a linear run of n nodes based on the current default parent
    "." is a single node based on the current default parent
    "$" resets the default parent to -1 (implied at the start);
        otherwise the default parent is always the last node created
    "<p" sets the default parent to the backref p
    "*p" is a fork at parent p, where p is a backref
    "*p1/p2/.../pn" is a merge of parents p1..pn, where the pi are backrefs
    "/p2/.../pn" is a merge of the preceding node and p2..pn
    ":name" defines a label for the preceding node; labels can be redefined
    "@text" emits an annotation event for text
    "!command" emits an action event for the current node
    "!!my command\n" is like "!", but to the end of the line
    "#...\n" is a comment up to the end of the line

    Whitespace between the above elements is ignored.

    A backref is either
     * a number n, which references the node curr-n, where curr is the current
       node, or
     * the name of a label you placed earlier using ":name", or
     * empty to denote the default parent.

    All string valued-elements are either strictly alphanumeric, or must
    be enclosed in double quotes ("..."), with "\" as escape character.

    Generates sequence of

      ('n', (id, [parentids])) for node creation
      ('l', (id, labelname)) for labels on nodes
      ('a', text) for annotations
      ('c', command) for actions (!)
      ('C', command) for line actions (!!)

    Examples
    --------

    Example of a complex graph (output not shown for brevity):

        >>> len(list(parsedag(b"""
        ...
        ... +3         # 3 nodes in linear run
        ... :forkhere  # a label for the last of the 3 nodes from above
        ... +5         # 5 more nodes on one branch
        ... :mergethis # label again
        ... <forkhere  # set default parent to labeled fork node
        ... +10        # 10 more nodes on a parallel branch
        ... @stable    # following nodes will be annotated as "stable"
        ... +5         # 5 nodes in stable
        ... !addfile   # custom command; could trigger new file in next node
        ... +2         # two more nodes
        ... /mergethis # merge last node with labeled node
        ... +4         # 4 more nodes descending from merge node
        ...
        ... """)))
        34

    Empty list:

        >>> list(parsedag(b""))
        []

    A simple linear run:

        >>> list(parsedag(b"+3"))
        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [1]))]

    Some non-standard ways to define such runs:

        >>> list(parsedag(b"+1+2"))
        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [1]))]

        >>> list(parsedag(b"+1*1*"))
        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [1]))]

        >>> list(parsedag(b"*"))
        [('n', (0, [-1]))]

        >>> list(parsedag(b"..."))
        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [1]))]

    A fork and a join, using numeric back references:

        >>> list(parsedag(b"+2*2*/2"))
        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [0])), ('n', (3, [2, 1]))]

        >>> list(parsedag(b"+2<2+1/2"))
        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [0])), ('n', (3, [2, 1]))]

    Placing a label:

        >>> list(parsedag(b"+1 :mylabel +1"))
        [('n', (0, [-1])), ('l', (0, 'mylabel')), ('n', (1, [0]))]

    An empty label (silly, really):

        >>> list(parsedag(b"+1:+1"))
        [('n', (0, [-1])), ('l', (0, '')), ('n', (1, [0]))]

    Fork and join, but with labels instead of numeric back references:

        >>> list(parsedag(b"+1:f +1:p2 *f */p2"))
        [('n', (0, [-1])), ('l', (0, 'f')), ('n', (1, [0])), ('l', (1, 'p2')),
         ('n', (2, [0])), ('n', (3, [2, 1]))]

        >>> list(parsedag(b"+1:f +1:p2 <f +1 /p2"))
        [('n', (0, [-1])), ('l', (0, 'f')), ('n', (1, [0])), ('l', (1, 'p2')),
         ('n', (2, [0])), ('n', (3, [2, 1]))]

    Restarting from the root:

        >>> list(parsedag(b"+1 $ +1"))
        [('n', (0, [-1])), ('n', (1, [-1]))]

    Annotations, which are meant to introduce sticky state for subsequent nodes:

        >>> list(parsedag(b"+1 @ann +1"))
        [('n', (0, [-1])), ('a', 'ann'), ('n', (1, [0]))]

        >>> list(parsedag(b'+1 @"my annotation" +1'))
        [('n', (0, [-1])), ('a', 'my annotation'), ('n', (1, [0]))]

    Commands, which are meant to operate on the most recently created node:

        >>> list(parsedag(b"+1 !cmd +1"))
        [('n', (0, [-1])), ('c', 'cmd'), ('n', (1, [0]))]

        >>> list(parsedag(b'+1 !"my command" +1'))
        [('n', (0, [-1])), ('c', 'my command'), ('n', (1, [0]))]

        >>> list(parsedag(b'+1 !!my command line\\n +1'))
        [('n', (0, [-1])), ('C', 'my command line'), ('n', (1, [0]))]

    Comments, which extend to the end of the line:

        >>> list(parsedag(b'+1 # comment\\n+1'))
        [('n', (0, [-1])), ('n', (1, [0]))]

    Error:

        >>> try: list(parsedag(b'+1 bad'))
        ... except Exception as e: print(pycompat.sysstr(bytes(e)))
        invalid character in dag description: bad...

    '''
    if not desc:
        return

    wordchars = pycompat.bytestr(string.ascii_letters + string.digits)

    labels = {}
    p1 = -1
    r = 0

    def resolve(ref):
        if not ref:
            return p1
        elif ref[0] in pycompat.bytestr(string.digits):
            return r - int(ref)
        else:
            return labels[ref]

    chiter = pycompat.iterbytestr(desc)

    def nextch():
        return next(chiter, '\0')

    def nextrun(c, allow):
        s = ''
        while c in allow:
            s += c
            c = nextch()
        return c, s

    def nextdelimited(c, limit, escape):
        s = ''
        while c != limit:
            if c == escape:
                c = nextch()
            s += c
            c = nextch()
        return nextch(), s

    def nextstring(c):
        if c == '"':
            return nextdelimited(nextch(), '"', '\\')
        else:
            return nextrun(c, wordchars)

    c = nextch()
    while c != '\0':
        while c in pycompat.bytestr(string.whitespace):
            c = nextch()
        if c == '.':
            yield 'n', (r, [p1])
            p1 = r
            r += 1
            c = nextch()
        elif c == '+':
            c, digs = nextrun(nextch(), pycompat.bytestr(string.digits))
            n = int(digs)
            for i in pycompat.xrange(0, n):
                yield 'n', (r, [p1])
                p1 = r
                r += 1
        elif c in '*/':
            if c == '*':
                c = nextch()
            c, pref = nextstring(c)
            prefs = [pref]
            while c == '/':
                c, pref = nextstring(nextch())
                prefs.append(pref)
            ps = [resolve(ref) for ref in prefs]
            yield 'n', (r, ps)
            p1 = r
            r += 1
        elif c == '<':
            c, ref = nextstring(nextch())
            p1 = resolve(ref)
        elif c == ':':
            c, name = nextstring(nextch())
            labels[name] = p1
            yield 'l', (p1, name)
        elif c == '@':
            c, text = nextstring(nextch())
            yield 'a', text
        elif c == '!':
            c = nextch()
            if c == '!':
                cmd = ''
                c = nextch()
                while c not in '\n\r\0':
                    cmd += c
                    c = nextch()
                yield 'C', cmd
            else:
                c, cmd = nextstring(c)
                yield 'c', cmd
        elif c == '#':
            while c not in '\n\r\0':
                c = nextch()
        elif c == '$':
            p1 = -1
            c = nextch()
        elif c == '\0':
            return # in case it was preceded by whitespace
        else:
            s = ''
            i = 0
            while c != '\0' and i < 10:
                s += c
                i += 1
                c = nextch()
            raise error.Abort(_('invalid character in dag description: '
                               '%s...') % s)

def dagtextlines(events,
                 addspaces=True,
                 wraplabels=False,
                 wrapannotations=False,
                 wrapcommands=False,
                 wrapnonlinear=False,
                 usedots=False,
                 maxlinewidth=70):
    '''generates single lines for dagtext()'''

    def wrapstring(text):
        if re.match("^[0-9a-z]*$", text):
            return text
        return '"' + text.replace('\\', '\\\\').replace('"', '\"') + '"'

    def gen():
        labels = {}
        run = 0
        wantr = 0
        needroot = False
        for kind, data in events:
            if kind == 'n':
                r, ps = data

                # sanity check
                if r != wantr:
                    raise error.Abort(_("expected id %i, got %i") % (wantr, r))
                if not ps:
                    ps = [-1]
                else:
                    for p in ps:
                        if p >= r:
                            raise error.Abort(_("parent id %i is larger than "
                                               "current id %i") % (p, r))
                wantr += 1

                # new root?
                p1 = r - 1
                if len(ps) == 1 and ps[0] == -1:
                    if needroot:
                        if run:
                            yield '+%d' % run
                            run = 0
                        if wrapnonlinear:
                            yield '\n'
                        yield '$'
                        p1 = -1
                    else:
                        needroot = True
                if len(ps) == 1 and ps[0] == p1:
                    if usedots:
                        yield "."
                    else:
                        run += 1
                else:
                    if run:
                        yield '+%d' % run
                        run = 0
                    if wrapnonlinear:
                        yield '\n'
                    prefs = []
                    for p in ps:
                        if p == p1:
                            prefs.append('')
                        elif p in labels:
                            prefs.append(labels[p])
                        else:
                            prefs.append('%d' % (r - p))
                    yield '*' + '/'.join(prefs)
            else:
                if run:
                    yield '+%d' % run
                    run = 0
                if kind == 'l':
                    rid, name = data
                    labels[rid] = name
                    yield ':' + name
                    if wraplabels:
                        yield '\n'
                elif kind == 'c':
                    yield '!' + wrapstring(data)
                    if wrapcommands:
                        yield '\n'
                elif kind == 'C':
                    yield '!!' + data
                    yield '\n'
                elif kind == 'a':
                    if wrapannotations:
                        yield '\n'
                    yield '@' + wrapstring(data)
                elif kind == '#':
                    yield '#' + data
                    yield '\n'
                else:
                    raise error.Abort(_("invalid event type in dag: "
                                        "('%s', '%s')")
                                      % (stringutil.escapestr(kind),
                                         stringutil.escapestr(data)))
        if run:
            yield '+%d' % run

    line = ''
    for part in gen():
        if part == '\n':
            if line:
                yield line
                line = ''
        else:
            if len(line) + len(part) >= maxlinewidth:
                yield line
                line = ''
            elif addspaces and line and part != '.':
                line += ' '
            line += part
    if line:
        yield line

def dagtext(dag,
            addspaces=True,
            wraplabels=False,
            wrapannotations=False,
            wrapcommands=False,
            wrapnonlinear=False,
            usedots=False,
            maxlinewidth=70):
    '''generates lines of a textual representation for a dag event stream

    events should generate what parsedag() does, so:

      ('n', (id, [parentids])) for node creation
      ('l', (id, labelname)) for labels on nodes
      ('a', text) for annotations
      ('c', text) for commands
      ('C', text) for line commands ('!!')
      ('#', text) for comment lines

    Parent nodes must come before child nodes.

    Examples
    --------

    Linear run:

        >>> dagtext([(b'n', (0, [-1])), (b'n', (1, [0]))])
        '+2'

    Two roots:

        >>> dagtext([(b'n', (0, [-1])), (b'n', (1, [-1]))])
        '+1 $ +1'

    Fork and join:

        >>> dagtext([(b'n', (0, [-1])), (b'n', (1, [0])), (b'n', (2, [0])),
        ...          (b'n', (3, [2, 1]))])
        '+2 *2 */2'

    Fork and join with labels:

        >>> dagtext([(b'n', (0, [-1])), (b'l', (0, b'f')), (b'n', (1, [0])),
        ...          (b'l', (1, b'p2')), (b'n', (2, [0])), (b'n', (3, [2, 1]))])
        '+1 :f +1 :p2 *f */p2'

    Annotations:

        >>> dagtext([(b'n', (0, [-1])), (b'a', b'ann'), (b'n', (1, [0]))])
        '+1 @ann +1'

        >>> dagtext([(b'n', (0, [-1])),
        ...          (b'a', b'my annotation'),
        ...          (b'n', (1, [0]))])
        '+1 @"my annotation" +1'

    Commands:

        >>> dagtext([(b'n', (0, [-1])), (b'c', b'cmd'), (b'n', (1, [0]))])
        '+1 !cmd +1'

        >>> dagtext([(b'n', (0, [-1])),
        ...          (b'c', b'my command'),
        ...          (b'n', (1, [0]))])
        '+1 !"my command" +1'

        >>> dagtext([(b'n', (0, [-1])),
        ...          (b'C', b'my command line'),
        ...          (b'n', (1, [0]))])
        '+1 !!my command line\\n+1'

    Comments:

        >>> dagtext([(b'n', (0, [-1])), (b'#', b' comment'), (b'n', (1, [0]))])
        '+1 # comment\\n+1'

        >>> dagtext([])
        ''

    Combining parsedag and dagtext:

        >>> dagtext(parsedag(b'+1 :f +1 :p2 *f */p2'))
        '+1 :f +1 :p2 *f */p2'

    '''
    return "\n".join(dagtextlines(dag,
                                  addspaces,
                                  wraplabels,
                                  wrapannotations,
                                  wrapcommands,
                                  wrapnonlinear,
                                  usedots,
                                  maxlinewidth))