view tests/test-trusted.py.out @ 51681:522b4d729e89

mmap: populate the mapping by default

Without pre-population, accessing all data through a mmap can result in many
pagefault, reducing performance significantly. If the mmap is prepopulated, the
performance can no longer get slower than a full read.
(See benchmark number below)

In some cases were very few data is read, prepopulating can be overkill and
slower than populating on access (through page fault). So that behavior can be
controlled when the caller can pre-determine the best behavior.
(See benchmark number below)

In addition, testing with populating in a secondary thread yield great result
combining the best of each approach. This might be implemented in later
changesets.

In all cases, using mmap has a great effect on memory usage when many processes
run in parallel on the same machine.

### Benchmarks

# What did I run

A couple of month back I ran a large benchmark campaign to assess the impact of
various approach for using mmap with the revlog (and other files), it
highlighted a few benchmarks that capture the impact of the changes well. So to
validate this change I checked the following:

- log command displaying various revisions
  (read the changelog index)
- log command displaying the patch of listed revisions
  (read the changelog index, the manifest index and a few files indexes)
- unbundling a few revisions
  (read and write changelog, manifest and few files indexes, and walk the graph
  to update some cache)
- pushing a few revisions
  (read and write changelog, manifest and few files indexes, walk the graph to
  update some cache, performs various accesses locally and remotely during
  discovery)

Benchmarks were run using the default module policy (c+py) and the rust one. No
significant difference were found between the two implementation, so we will
present result using the default policy (unless otherwise specified).

I ran them on a few repositories :

- mercurial: a "public changeset only" copy of mercurial from 2018-08-01 using
  zstd compression and sparse-revlog

- pypy: a copy of pypy from 2018-08-01 using zstd compression and sparse-revlog

- netbeans: a copy of netbeans from 2018-08-01 using zstd compression and
  sparse-revlog

- mozilla-try: a copy of mozilla-try from 2019-02-18 using zstd compression and
  sparse-revlog

- mozilla-try persistent-nodemap: Same as the above but with a persistent
  nodemap. Used for the log --patch benchmark only

# Results

For the smaller repositories (mercurial, pypy), the impact of mmap is almost
imperceptible, other cost dominating the operation. The impact of prepopulating
is undiscernible in the benchmark we ran.

For larger repositories the benchmark support explanation given above:

On netbeans, the log can be about 1% faster without repopulation (for a
difference < 100ms) but unbundle becomes a bit slower, even when small.

### data-env-vars.name                             = netbeans-2018-08-01-zstd-sparse-revlog
  # benchmark.name                                 = hg.command.unbundle
  # benchmark.variants.issue6528                   = disabled
  # benchmark.variants.reuse-external-delta-parent = yes
  # benchmark.variants.revs                        = any-1-extra-rev
  # benchmark.variants.source                      = unbundle
  # benchmark.variants.verbosity                   = quiet
with-populate: 0.240157
no-populate:   0.265087  (+10.38%, +0.02)
  # benchmark.variants.revs                        = any-100-extra-rev
with-populate: 1.459518
no-populate:   1.481290   (+1.49%, +0.02)
 ## benchmark.name                                 = hg.command.push
  # benchmark.variants.explicit-rev                = none
  # benchmark.variants.issue6528                   = disabled
  # benchmark.variants.protocol                    = ssh
  # benchmark.variants.reuse-external-delta-parent = yes
  # benchmark.variants.revs                        = any-1-extra-rev
with-populate: 0.771919
no-populate:   0.792025   (+2.60%, +0.02)
  # benchmark.variants.revs                        = any-100-extra-rev
with-populate: 1.459518
no-populate:   1.481290   (+1.49%, +0.02)


For mozilla-try, the "slow down" from pre-populate for small `hg log` is more
visible, but still small in absolute time. (using rust value for the persistent
nodemap value to be relevant).

### data-env-vars.name            = mozilla-try-2019-02-18-ds2-pnm
  # benchmark.name                = hg.command.log
  # bin-env-vars.hg.flavor        = rust
  # benchmark.variants.patch      = yes
  # benchmark.variants.limit-rev  = 1
with-populate: 0.237813
no-populate:   0.229452   (-3.52%, -0.01)
  # benchmark.variants.limit-rev  = 10
  # benchmark.variants.patch      = yes
with-populate: 1.213578
no-populate:   1.205189
### data-env-vars.name            = mozilla-try-2019-02-18-zstd-sparse-revlog
  # benchmark.variants.limit-rev  = 1000
  # benchmark.variants.patch      = no
  # benchmark.variants.rev        = tip
with-populate: 0.198607
no-populate:   0.195038   (-1.80%, -0.00)

However pre-populating provide a significant boost on more complex operations
like unbundle or push:

### data-env-vars.name                             = mozilla-try-2019-02-18-zstd-sparse-revlog
  # benchmark.name                                 = hg.command.push
  # benchmark.variants.explicit-rev                = none
  # benchmark.variants.issue6528                   = disabled
  # benchmark.variants.protocol                    = ssh
  # benchmark.variants.reuse-external-delta-parent = yes
  # benchmark.variants.revs                        = any-1-extra-rev
with-populate: 4.798632
no-populate:   4.953295   (+3.22%, +0.15)
  # benchmark.variants.revs                        = any-100-extra-rev
with-populate: 4.903618
no-populate:   5.014963   (+2.27%, +0.11)
 ## benchmark.name                                 = hg.command.unbundle
  # benchmark.variants.revs                        = any-1-extra-rev
with-populate: 1.423411
no-populate:   1.585365  (+11.38%, +0.16)
  # benchmark.variants.revs                        = any-100-extra-rev
with-populate: 1.537909
no-populate:   1.688489   (+9.79%, +0.15)

# same user, same group
trusted
    global = /some/path
    local = /another/path
untrusted
. . global = /some/path
. . local = /another/path

# same user, different group
trusted
    global = /some/path
    local = /another/path
untrusted
. . global = /some/path
. . local = /another/path

# different user, same group
not trusting file .hg/hgrc from untrusted user abc, group bar
trusted
    global = /some/path
untrusted
. . global = /some/path
. . local = /another/path

# different user, same group, but we trust the group
trusted
    global = /some/path
    local = /another/path
untrusted
. . global = /some/path
. . local = /another/path

# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
trusted
    global = /some/path
untrusted
. . global = /some/path
. . local = /another/path

# different user, different group, but we trust the user
trusted
    global = /some/path
    local = /another/path
untrusted
. . global = /some/path
. . local = /another/path

# different user, different group, but we trust the group
trusted
    global = /some/path
    local = /another/path
untrusted
. . global = /some/path
. . local = /another/path

# different user, different group, but we trust the user and the group
trusted
    global = /some/path
    local = /another/path
untrusted
. . global = /some/path
. . local = /another/path

# we trust all users
# different user, different group
trusted
    global = /some/path
    local = /another/path
untrusted
. . global = /some/path
. . local = /another/path

# we trust all groups
# different user, different group
trusted
    global = /some/path
    local = /another/path
untrusted
. . global = /some/path
. . local = /another/path

# we trust all users and groups
# different user, different group
trusted
    global = /some/path
    local = /another/path
untrusted
. . global = /some/path
. . local = /another/path

# we don't get confused by users and groups with the same name
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
trusted
    global = /some/path
untrusted
. . global = /some/path
. . local = /another/path

# list of user names
# different user, different group, but we trust the user
trusted
    global = /some/path
    local = /another/path
untrusted
. . global = /some/path
. . local = /another/path

# list of group names
# different user, different group, but we trust the group
trusted
    global = /some/path
    local = /another/path
untrusted
. . global = /some/path
. . local = /another/path

# Can't figure out the name of the user running this process
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
trusted
    global = /some/path
untrusted
. . global = /some/path
. . local = /another/path

# prints debug warnings
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
trusted
ignoring untrusted configuration option paths.local = /another/path
    global = /some/path
untrusted
. . global = /some/path
. ignoring untrusted configuration option paths.local = /another/path
. local = /another/path

# report_untrusted enabled without debug hides warnings
# different user, different group
trusted
    global = /some/path
untrusted
. . global = /some/path
. . local = /another/path

# report_untrusted enabled with debug shows warnings
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
trusted
ignoring untrusted configuration option paths.local = /another/path
    global = /some/path
untrusted
. . global = /some/path
. ignoring untrusted configuration option paths.local = /another/path
. local = /another/path

# ui.readconfig sections
quux

# read trusted, untrusted, new ui, trusted
not trusting file foobar from untrusted user abc, group def
trusted:
ignoring untrusted configuration option foobar.baz = quux
None
untrusted:
quux

# error handling
# file doesn't exist
# same user, same group
# different user, different group

# parse error
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
ignored .hg/hgrc:1: foo
# same user, same group
config error at .hg/hgrc:1: foo


# access typed information
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
# suboptions, trusted and untrusted
(None, []) ('main', [('one', 'one'), ('two', 'two')])
# path, trusted and untrusted
None .hg/monty/python
# bool, trusted and untrusted
False True
# int, trusted and untrusted
0 42
# bytes, trusted and untrusted
0 84934656
# list, trusted and untrusted
[] ['spam', 'ham', 'eggs']