tests/test-pushvars.t

util: lower water mark when removing nodes after cost limit reached

See the inline comment for the reasoning here. This is a pretty
common strategy for garbage collectors, other cache-like primtives.

The performance impact is substantial:

$ hg perflrucachedict --size 4 --gets 1000000 --sets 1000000 --mixed 1000000 --costlimit 100
! inserts w/ cost limit
! wall 1.659181 comb 1.650000 user 1.650000 sys 0.000000 (best of 7)
! wall 1.722122 comb 1.720000 user 1.720000 sys 0.000000 (best of 6)
! mixed w/ cost limit
! wall 1.139955 comb 1.140000 user 1.140000 sys 0.000000 (best of 9)
! wall 1.182513 comb 1.180000 user 1.180000 sys 0.000000 (best of 9)

$ hg perflrucachedict --size 1000 --gets 1000000 --sets 1000000 --mixed 1000000 --costlimit 10000
! inserts
! wall 0.679546 comb 0.680000 user 0.680000 sys 0.000000 (best of 15)
! sets
! wall 0.825147 comb 0.830000 user 0.830000 sys 0.000000 (best of 13)
! inserts w/ cost limit
! wall 25.105273 comb 25.080000 user 25.080000 sys 0.000000 (best of 3)
! wall  1.724397 comb  1.720000 user  1.720000 sys 0.000000 (best of 6)
! mixed
! wall 0.807096 comb 0.810000 user 0.810000 sys 0.000000 (best of 13)
! mixed w/ cost limit
! wall 12.104470 comb 12.070000 user 12.070000 sys 0.000000 (best of 3)
! wall  1.190563 comb  1.190000 user  1.190000 sys 0.000000 (best of 9)

$ hg perflrucachedict --size 1000 --gets 1000000 --sets 1000000 --mixed 1000000 --costlimit 10000 --mixedgetfreq 90
! inserts
! wall 0.711177 comb 0.710000 user 0.710000 sys 0.000000 (best of 14)
! sets
! wall 0.846992 comb 0.850000 user 0.850000 sys 0.000000 (best of 12)
! inserts w/ cost limit
! wall 25.963028 comb 25.960000 user 25.960000 sys 0.000000 (best of 3)
! wall  2.184311 comb  2.180000 user  2.180000 sys 0.000000 (best of 5)
! mixed
! wall 0.728256 comb 0.730000 user 0.730000 sys 0.000000 (best of 14)
! mixed w/ cost limit
! wall 3.174256 comb 3.170000 user 3.170000 sys 0.000000 (best of 4)
! wall 0.773186 comb 0.770000 user 0.770000 sys 0.000000 (best of 13)

$ hg perflrucachedict --size 100000 --gets 1000000 --sets 1000000 --mixed 1000000 --mixedgetfreq 90 --costlimit 5000000
! gets
! wall 1.191368 comb 1.190000 user 1.190000 sys 0.000000 (best of 9)
! wall 1.195304 comb 1.190000 user 1.190000 sys 0.000000 (best of 9)
! inserts
! wall 0.950995 comb 0.950000 user 0.950000 sys 0.000000 (best of 11)
! inserts w/ cost limit
! wall 1.589732 comb 1.590000 user 1.590000 sys 0.000000 (best of 7)
! sets
! wall 1.094941 comb 1.100000 user 1.090000 sys 0.010000 (best of 9)
! mixed
! wall 0.936420 comb 0.940000 user 0.930000 sys 0.010000 (best of 10)
! mixed w/ cost limit
! wall 0.882780 comb 0.870000 user 0.870000 sys 0.000000 (best of 11)

This puts us ~2x slower than caches without cost accounting. And for
read-heavy workloads (the prime use cases for caches), performance is
nearly identical.

In the worst case (pure write workloads with cost accounting enabled),
we're looking at ~1.5us per insert on large caches. That seems "fast
enough."

Differential Revision: https://phab.mercurial-scm.org/D4505

Setup

  $ PYTHONPATH=$TESTDIR/..:$PYTHONPATH
  $ export PYTHONPATH

  $ cat > $TESTTMP/pretxnchangegroup.sh << EOF
  > #!/bin/sh
  > env | egrep "^HG_USERVAR_(DEBUG|BYPASS_REVIEW)" | sort
  > exit 0
  > EOF
  $ cat >> $HGRCPATH << EOF
  > [hooks]
  > pretxnchangegroup = sh $TESTTMP/pretxnchangegroup.sh
  > EOF

  $ hg init repo
  $ hg clone -q repo child
  $ cd child

Test pushing vars to repo with pushvars.server not set

  $ echo b > a
  $ hg commit -Aqm a
  $ hg push --pushvars "DEBUG=1" --pushvars "BYPASS_REVIEW=true"
  pushing to $TESTTMP/repo
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files

Setting pushvars.sever = true and then pushing.

  $ echo [push] >> $HGRCPATH
  $ echo "pushvars.server = true" >> $HGRCPATH
  $ echo b >> a
  $ hg commit -Aqm a
  $ hg push --pushvars "DEBUG=1" --pushvars "BYPASS_REVIEW=true"
  pushing to $TESTTMP/repo
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  HG_USERVAR_BYPASS_REVIEW=true
  HG_USERVAR_DEBUG=1

Test pushing var with empty right-hand side

  $ echo b >> a
  $ hg commit -Aqm a
  $ hg push --pushvars "DEBUG="
  pushing to $TESTTMP/repo
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  HG_USERVAR_DEBUG=

Test pushing bad vars

  $ echo b >> a
  $ hg commit -Aqm b
  $ hg push --pushvars "DEBUG"
  pushing to $TESTTMP/repo
  searching for changes
  abort: unable to parse variable 'DEBUG', should follow 'KEY=VALUE' or 'KEY=' format
  [255]