view tests/test-import-unknown.t @ 44363:f7459da77f23

nodemap: introduce an option to use mmap to read the nodemap mapping

The performance and memory benefit is much greater if we don't have to copy all
the data in memory for each information. So we introduce an option (on by
default) to read the data using mmap.

This changeset is the last one definition the API for index support nodemap
data. (they have to be able to use the mmaping).

Below are some benchmark comparing the best we currently have in 5.3 with the
final step of this series (using the persistent nodemap implementation in
Rust). The benchmark run `hg perfindex` with various revset and the following
variants:

Before:

 * do not use the persistent nodemap
 * use the CPython implementation of the index for nodemap
 * use mmapping of the changelog index

After:

 * use the MixedIndex Rust code, with the NodeTree object for nodemap access
   (still in review)
 * use the persistent nodemap data from disk
 * access the persistent nodemap data through mmap
 * use mmapping of the changelog index

The persistent nodemap greatly speed up  most operation on very large
repositories. Some of the previously very fast lookup end up a bit slower because
the persistent nodemap has to be setup. However the absolute slowdown is very
small and won't matters in the big picture.

Here are some numbers (in seconds) for the reference copy of mozilla-try:

Revset            Before   After     abs-change speedup

-10000:           0.004622 0.005532   0.000910  ×   0.83
-10:              0.000050 0.000132   0.000082  ×   0.37
tip               0.000052 0.000085   0.000033  ×   0.61
0 + (-10000:)     0.028222 0.005337  -0.022885  ×   5.29
0                 0.023521 0.000084  -0.023437  × 280.01
(-10000:) + 0     0.235539 0.005308  -0.230231  ×  44.37
(-10:) + :9       0.232883 0.000180  -0.232703  ×1293.79
(-10000:) + (:99) 0.238735 0.005358  -0.233377  ×  44.55
:99 + (-10000:)   0.317942 0.005593  -0.312349  ×  56.84
:9 + (-10:)       0.313372 0.000179  -0.313193  ×1750.68
:9                0.316450 0.000143  -0.316307  ×2212.93


On smaller repositories, the cost of nodemap related operation is not as big, so
the win is much more modest. Yet it helps shaving a handful of millisecond here
and there.

Here are some numbers (in seconds) for the reference copy of mercurial:

Revset            Before   After     abs-change speedup
-10:              0.000065 0.000097   0.000032  × 0.67
tip               0.000063 0.000078   0.000015  × 0.80
0                 0.000561 0.000079  -0.000482  × 7.10
-10000:           0.004609 0.003648  -0.000961  × 1.26
0 + (-10000:)     0.005023 0.003715  -0.001307  × 1.35
(-10:) + :9       0.002187 0.000108  -0.002079  ×20.25
(-10000:) + 0     0.006252 0.003716  -0.002536  × 1.68
(-10000:) + (:99) 0.006367 0.003707  -0.002660  × 1.71
:9 + (-10:)       0.003846 0.000110  -0.003736  ×34.96
:9                0.003854 0.000099  -0.003755  ×38.92
:99 + (-10000:)   0.007644 0.003778  -0.003866  × 2.02

Differential Revision: https://phab.mercurial-scm.org/D7894

  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > purge =
  > EOF

  $ hg init test
  $ cd test
  $ echo a > changed
  $ echo a > removed
  $ echo a > source
  $ hg ci -Am addfiles
  adding changed
  adding removed
  adding source
  $ echo a >> changed
  $ echo a > added
  $ hg add added
  $ hg rm removed
  $ hg cp source copied
  $ hg diff --git > ../unknown.diff

Test adding on top of an unknown file

  $ hg up -qC 0
  $ hg purge
  $ echo a > added
  $ hg import --no-commit ../unknown.diff
  applying ../unknown.diff
  file added already exists
  1 out of 1 hunks FAILED -- saving rejects to file added.rej
  abort: patch failed to apply
  [255]

Test modifying an unknown file

  $ hg revert -aq
  $ hg purge
  $ hg rm changed
  $ hg ci -m removechanged
  $ echo a > changed
  $ hg import --no-commit ../unknown.diff
  applying ../unknown.diff
  abort: cannot patch changed: file is not tracked
  [255]

Test removing an unknown file

  $ hg up -qC 0
  $ hg purge
  $ hg rm removed
  $ hg ci -m removeremoved
  created new head
  $ echo a > removed
  $ hg import --no-commit ../unknown.diff
  applying ../unknown.diff
  abort: cannot patch removed: file is not tracked
  [255]

Test copying onto an unknown file

  $ hg up -qC 0
  $ hg purge
  $ echo a > copied
  $ hg import --no-commit ../unknown.diff
  applying ../unknown.diff
  abort: cannot create copied: destination already exists
  [255]

  $ cd ..