view doc/check-seclevel.py @ 29830:92ac2baaea86

revlog: use an LRU cache for delta chain bases

Profiling using statprof revealed a hotspot during changegroup
application calculating delta chain bases on generaldelta repos.
Essentially, revlog._addrevision() was performing a lot of redundant
work tracing the delta chain as part of determining when the chain
distance was acceptable. This was most pronounced when adding
revisions to manifests, which can have delta chains thousands of
revisions long.

There was a delta chain base cache on revlogs before, but it only
captured a single revision. This was acceptable before generaldelta,
when _addrevision would build deltas from the previous revision and
thus we'd pretty much guarantee a cache hit when resolving the delta
chain base on a subsequent _addrevision call. However, it isn't
suitable for generaldelta because parent revisions aren't necessarily
the last processed revision.

This patch converts the delta chain base cache to an LRU dict cache.
The cache can hold multiple entries, so generaldelta repos have a
higher chance of getting a cache hit.

The impact of this change when processing changegroup additions is
significant. On a generaldelta conversion of the "mozilla-unified"
repo (which contains heads of the main Firefox repositories in
chronological order - this means there are lots of transitions between
heads in revlog order), this change has the following impact when
performing an `hg unbundle` of an uncompressed bundle of the repo:

before: 5:42 CPU time
after:  4:34 CPU time

Most of this time is saved when applying the changelog and manifest
revlogs:

before: 2:30 CPU time
after:  1:17 CPU time

That nearly a 50% reduction in CPU time applying changesets and
manifests!

Applying a gzipped bundle of the same repo (effectively simulating a
`hg clone` over HTTP) showed a similar speedup:

before: 5:53 CPU time
after:  4:46 CPU time

Wall time improvements were basically the same as CPU time.

I didn't measure explicitly, but it feels like most of the time
is saved when processing manifests. This makes sense, as large
manifests tend to have very long delta chains and thus benefit the
most from this cache.

So, this change effectively makes changegroup application (which is
used by `hg unbundle`, `hg clone`, `hg pull`, `hg unshelve`, and
various other commands) significantly faster when delta chains are
long (which can happen on repos with large numbers of files and thus
large manifests).

In theory, this change can result in more memory utilization. However,
we're caching a dict of ints. At most we have 200 ints + Python object
overhead per revlog. And, the cache is really only populated when
performing read-heavy operations, such as adding changegroups or
scanning an individual revlog. For memory bloat to be an issue, we'd
need to scan/read several revisions from several revlogs all while
having active references to several revlogs. I don't think there are
many operations that do this, so I don't think memory bloat from the
cache will be an issue.

#!/usr/bin/env python
#
# checkseclevel - checking section title levels in each online help document

from __future__ import absolute_import

import optparse
import os
import sys

# import from the live mercurial repo
os.environ['HGMODULEPOLICY'] = 'py'
sys.path.insert(0, "..")
from mercurial import demandimport; demandimport.enable()
from mercurial import (
    commands,
    extensions,
    help,
    minirst,
    ui as uimod,
)

table = commands.table
helptable = help.helptable

level2mark = ['"', '=', '-', '.', '#']
reservedmarks = ['"']

mark2level = {}
for m, l in zip(level2mark, xrange(len(level2mark))):
    if m not in reservedmarks:
        mark2level[m] = l

initlevel_topic = 0
initlevel_cmd = 1
initlevel_ext = 1
initlevel_ext_cmd = 3

def showavailables(ui, initlevel):
    ui.warn(('    available marks and order of them in this help: %s\n') %
            (', '.join(['%r' % (m * 4) for m in level2mark[initlevel + 1:]])))

def checkseclevel(ui, doc, name, initlevel):
    ui.note(('checking "%s"\n') % name)
    blocks, pruned = minirst.parse(doc, 0, ['verbose'])
    errorcnt = 0
    curlevel = initlevel
    for block in blocks:
        if block['type'] != 'section':
            continue
        mark = block['underline']
        title = block['lines'][0]
        if (mark not in mark2level) or (mark2level[mark] <= initlevel):
            ui.warn(('invalid section mark %r for "%s" of %s\n') %
                    (mark * 4, title, name))
            showavailables(ui, initlevel)
            errorcnt += 1
            continue
        nextlevel = mark2level[mark]
        if curlevel < nextlevel and curlevel + 1 != nextlevel:
            ui.warn(('gap of section level at "%s" of %s\n') %
                    (title, name))
            showavailables(ui, initlevel)
            errorcnt += 1
            continue
        ui.note(('appropriate section level for "%s %s"\n') %
                (mark * (nextlevel * 2), title))
        curlevel = nextlevel

    return errorcnt

def checkcmdtable(ui, cmdtable, namefmt, initlevel):
    errorcnt = 0
    for k, entry in cmdtable.items():
        name = k.split("|")[0].lstrip("^")
        if not entry[0].__doc__:
            ui.note(('skip checking %s: no help document\n') %
                    (namefmt % name))
            continue
        errorcnt += checkseclevel(ui, entry[0].__doc__,
                                  namefmt % name,
                                  initlevel)
    return errorcnt

def checkhghelps(ui):
    errorcnt = 0
    for names, sec, doc in helptable:
        if callable(doc):
            doc = doc(ui)
        errorcnt += checkseclevel(ui, doc,
                                  '%s help topic' % names[0],
                                  initlevel_topic)

    errorcnt += checkcmdtable(ui, table, '%s command', initlevel_cmd)

    for name in sorted(extensions.enabled().keys() +
                       extensions.disabled().keys()):
        mod = extensions.load(ui, name, None)
        if not mod.__doc__:
            ui.note(('skip checking %s extension: no help document\n') % name)
            continue
        errorcnt += checkseclevel(ui, mod.__doc__,
                                  '%s extension' % name,
                                  initlevel_ext)

        cmdtable = getattr(mod, 'cmdtable', None)
        if cmdtable:
            errorcnt += checkcmdtable(ui, cmdtable,
                                      '%s command of ' + name + ' extension',
                                      initlevel_ext_cmd)
    return errorcnt

def checkfile(ui, filename, initlevel):
    if filename == '-':
        filename = 'stdin'
        doc = sys.stdin.read()
    else:
        with open(filename) as fp:
            doc = fp.read()

    ui.note(('checking input from %s with initlevel %d\n') %
            (filename, initlevel))
    return checkseclevel(ui, doc, 'input from %s' % filename, initlevel)

def main():
    optparser = optparse.OptionParser("""%prog [options]

This checks all help documents of Mercurial (topics, commands,
extensions and commands of them), if no file is specified by --file
option.
""")
    optparser.add_option("-v", "--verbose",
                         help="enable additional output",
                         action="store_true")
    optparser.add_option("-d", "--debug",
                         help="debug mode",
                         action="store_true")
    optparser.add_option("-f", "--file",
                         help="filename to read in (or '-' for stdin)",
                         action="store", default="")

    optparser.add_option("-t", "--topic",
                         help="parse file as help topic",
                         action="store_const", dest="initlevel", const=0)
    optparser.add_option("-c", "--command",
                         help="parse file as help of core command",
                         action="store_const", dest="initlevel", const=1)
    optparser.add_option("-e", "--extension",
                         help="parse file as help of extension",
                         action="store_const", dest="initlevel", const=1)
    optparser.add_option("-C", "--extension-command",
                         help="parse file as help of extension command",
                         action="store_const", dest="initlevel", const=3)

    optparser.add_option("-l", "--initlevel",
                         help="set initial section level manually",
                         action="store", type="int", default=0)

    (options, args) = optparser.parse_args()

    ui = uimod.ui()
    ui.setconfig('ui', 'verbose', options.verbose, '--verbose')
    ui.setconfig('ui', 'debug', options.debug, '--debug')

    if options.file:
        if checkfile(ui, options.file, options.initlevel):
            sys.exit(1)
    else:
        if checkhghelps(ui):
            sys.exit(1)

if __name__ == "__main__":
    main()