tests/test-wireproto-command-known.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

  $ . $TESTDIR/wireprotohelpers.sh

  $ hg init server
  $ enablehttpv2 server
  $ cd server
  $ hg debugdrawdag << EOF
  > C D
  > |/
  > B
  > |
  > A
  > EOF

  $ hg log -T '{rev}:{node} {desc}\n'
  3:be0ef73c17ade3fc89dc41701eb9fc3a91b58282 D
  2:26805aba1e600a82e93661149f2313866a221a7b C
  1:112478962961147124edd43549aedd1a335e44bf B
  0:426bada5c67598ca65036d57d9e4b64b0c1ce7a0 A

  $ hg serve -p $HGPORT -d --pid-file hg.pid -E error.log
  $ cat hg.pid > $DAEMON_PIDS

No arguments returns something reasonable

  $ sendhttpv2peer << EOF
  > command known
  > EOF
  creating http peer for wire protocol version 2
  sending known command
  s>     POST /api/exp-http-v2-0001/ro/known HTTP/1.1\r\n
  s>     Accept-Encoding: identity\r\n
  s>     accept: application/mercurial-exp-framing-0005\r\n
  s>     content-type: application/mercurial-exp-framing-0005\r\n
  s>     content-length: 20\r\n
  s>     host: $LOCALIP:$HGPORT\r\n (glob)
  s>     user-agent: Mercurial debugwireproto\r\n
  s>     \r\n
  s>     \x0c\x00\x00\x01\x00\x01\x01\x11\xa1DnameEknown
  s> makefile('rb', None)
  s>     HTTP/1.1 200 OK\r\n
  s>     Server: testing stub value\r\n
  s>     Date: $HTTP_DATE$\r\n
  s>     Content-Type: application/mercurial-exp-framing-0005\r\n
  s>     Transfer-Encoding: chunked\r\n
  s>     \r\n
  s>     13\r\n
  s>     \x0b\x00\x00\x01\x00\x02\x011
  s>     \xa1FstatusBok
  s>     \r\n
  received frame(size=11; request=1; stream=2; streamflags=stream-begin; type=command-response; flags=continuation)
  s>     9\r\n
  s>     \x01\x00\x00\x01\x00\x02\x001
  s>     @
  s>     \r\n
  received frame(size=1; request=1; stream=2; streamflags=; type=command-response; flags=continuation)
  s>     8\r\n
  s>     \x00\x00\x00\x01\x00\x02\x002
  s>     \r\n
  s>     0\r\n
  s>     \r\n
  received frame(size=0; request=1; stream=2; streamflags=; type=command-response; flags=eos)
  response: []

Single known node works

  $ sendhttpv2peer << EOF
  > command known
  >     nodes eval:[b'\x42\x6b\xad\xa5\xc6\x75\x98\xca\x65\x03\x6d\x57\xd9\xe4\xb6\x4b\x0c\x1c\xe7\xa0']
  > EOF
  creating http peer for wire protocol version 2
  sending known command
  s>     POST /api/exp-http-v2-0001/ro/known HTTP/1.1\r\n
  s>     Accept-Encoding: identity\r\n
  s>     accept: application/mercurial-exp-framing-0005\r\n
  s>     content-type: application/mercurial-exp-framing-0005\r\n
  s>     content-length: 54\r\n
  s>     host: $LOCALIP:$HGPORT\r\n (glob)
  s>     user-agent: Mercurial debugwireproto\r\n
  s>     \r\n
  s>     .\x00\x00\x01\x00\x01\x01\x11\xa2Dargs\xa1Enodes\x81TBk\xad\xa5\xc6u\x98\xcae\x03mW\xd9\xe4\xb6K\x0c\x1c\xe7\xa0DnameEknown
  s> makefile('rb', None)
  s>     HTTP/1.1 200 OK\r\n
  s>     Server: testing stub value\r\n
  s>     Date: $HTTP_DATE$\r\n
  s>     Content-Type: application/mercurial-exp-framing-0005\r\n
  s>     Transfer-Encoding: chunked\r\n
  s>     \r\n
  s>     13\r\n
  s>     \x0b\x00\x00\x01\x00\x02\x011
  s>     \xa1FstatusBok
  s>     \r\n
  received frame(size=11; request=1; stream=2; streamflags=stream-begin; type=command-response; flags=continuation)
  s>     a\r\n
  s>     \x02\x00\x00\x01\x00\x02\x001
  s>     A1
  s>     \r\n
  received frame(size=2; request=1; stream=2; streamflags=; type=command-response; flags=continuation)
  s>     8\r\n
  s>     \x00\x00\x00\x01\x00\x02\x002
  s>     \r\n
  s>     0\r\n
  s>     \r\n
  received frame(size=0; request=1; stream=2; streamflags=; type=command-response; flags=eos)
  response: [
    True
  ]

Multiple nodes works

  $ sendhttpv2peer << EOF
  > command known
  >     nodes eval:[b'\x42\x6b\xad\xa5\xc6\x75\x98\xca\x65\x03\x6d\x57\xd9\xe4\xb6\x4b\x0c\x1c\xe7\xa0', b'00000000000000000000', b'\x11\x24\x78\x96\x29\x61\x14\x71\x24\xed\xd4\x35\x49\xae\xdd\x1a\x33\x5e\x44\xbf']
  > EOF
  creating http peer for wire protocol version 2
  sending known command
  s>     POST /api/exp-http-v2-0001/ro/known HTTP/1.1\r\n
  s>     Accept-Encoding: identity\r\n
  s>     accept: application/mercurial-exp-framing-0005\r\n
  s>     content-type: application/mercurial-exp-framing-0005\r\n
  s>     content-length: 96\r\n
  s>     host: $LOCALIP:$HGPORT\r\n (glob)
  s>     user-agent: Mercurial debugwireproto\r\n
  s>     \r\n
  s>     X\x00\x00\x01\x00\x01\x01\x11\xa2Dargs\xa1Enodes\x83TBk\xad\xa5\xc6u\x98\xcae\x03mW\xd9\xe4\xb6K\x0c\x1c\xe7\xa0T00000000000000000000T\x11$x\x96)a\x14q$\xed\xd45I\xae\xdd\x1a3^D\xbfDnameEknown
  s> makefile('rb', None)
  s>     HTTP/1.1 200 OK\r\n
  s>     Server: testing stub value\r\n
  s>     Date: $HTTP_DATE$\r\n
  s>     Content-Type: application/mercurial-exp-framing-0005\r\n
  s>     Transfer-Encoding: chunked\r\n
  s>     \r\n
  s>     13\r\n
  s>     \x0b\x00\x00\x01\x00\x02\x011
  s>     \xa1FstatusBok
  s>     \r\n
  received frame(size=11; request=1; stream=2; streamflags=stream-begin; type=command-response; flags=continuation)
  s>     c\r\n
  s>     \x04\x00\x00\x01\x00\x02\x001
  s>     C101
  s>     \r\n
  received frame(size=4; request=1; stream=2; streamflags=; type=command-response; flags=continuation)
  s>     8\r\n
  s>     \x00\x00\x00\x01\x00\x02\x002
  s>     \r\n
  s>     0\r\n
  s>     \r\n
  received frame(size=0; request=1; stream=2; streamflags=; type=command-response; flags=eos)
  response: [
    True,
    False,
    True
  ]

  $ cat error.log