view tests/test-server-view.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

  $ hg init test
  $ cd test
  $ hg debugbuilddag '+2'
  $ hg phase --public 0

  $ hg serve -p $HGPORT -d --pid-file=hg.pid -E errors.log
  $ cat hg.pid >> $DAEMON_PIDS
  $ cd ..
  $ hg init test2
  $ cd test2
  $ hg incoming http://foo:xyzzy@localhost:$HGPORT/
  comparing with http://foo:***@localhost:$HGPORT/
  changeset:   0:1ea73414a91b
  user:        debugbuilddag
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     r0
  
  changeset:   1:66f7d451a68b
  tag:         tip
  user:        debugbuilddag
  date:        Thu Jan 01 00:00:01 1970 +0000
  summary:     r1
  
  $ killdaemons.py

  $ cd ..
  $ hg -R test --config server.view=immutable serve -p $HGPORT -d --pid-file=hg.pid -E errors.log
  $ cat hg.pid >> $DAEMON_PIDS
  $ hg -R test2 incoming http://foo:xyzzy@localhost:$HGPORT/
  comparing with http://foo:***@localhost:$HGPORT/
  changeset:   0:1ea73414a91b
  tag:         tip
  user:        debugbuilddag
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     r0
  

Check same result using `experimental.extra-filter-revs`

  $ hg -R test --config experimental.extra-filter-revs='not public()' serve -p $HGPORT1 -d --pid-file=hg2.pid -E errors.log
  $ cat hg2.pid >> $DAEMON_PIDS
  $ hg -R test2 incoming http://foo:xyzzy@localhost:$HGPORT1/
  comparing with http://foo:***@localhost:$HGPORT1/
  changeset:   0:1ea73414a91b
  tag:         tip
  user:        debugbuilddag
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     r0
  
  $ hg -R test --config experimental.extra-filter-revs='not public()' debugupdatecache
  $ ls -1 test/.hg/cache/
  branch2-base%89c45d2fa07e
  branch2-immutable%89c45d2fa07e
  branch2-served
  branch2-served%89c45d2fa07e
  branch2-served.hidden%89c45d2fa07e
  branch2-visible%89c45d2fa07e
  branch2-visible-hidden%89c45d2fa07e
  hgtagsfnodes1
  rbc-names-v1
  rbc-revs-v1
  tags2
  tags2-served%89c45d2fa07e

cleanup

  $ cat errors.log
  $ killdaemons.py