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
$ cat >> .hg/hgrc << EOF
> [web]
> push_ssl = false
> allow-push = *
> EOF
$ hg debugdrawdag << EOF
> C D
> |/
> B
> |
> A
> EOF
$ hg serve -p $HGPORT -d --pid-file hg.pid -E error.log
$ cat hg.pid > $DAEMON_PIDS
pushkey for a bookmark works
$ sendhttpv2peer << EOF
> command pushkey
> namespace bookmarks
> key @
> old
> new 426bada5c67598ca65036d57d9e4b64b0c1ce7a0
> EOF
creating http peer for wire protocol version 2
sending pushkey command
s> *\r\n (glob)
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: 105\r\n
s> host: $LOCALIP:$HGPORT\r\n (glob)
s> user-agent: Mercurial debugwireproto\r\n
s> \r\n
s> a\x00\x00\x01\x00\x01\x01\x11\xa2Dargs\xa4CkeyA@InamespaceIbookmarksCnewX(426bada5c67598ca65036d57d9e4b64b0c1ce7a0Cold@DnameGpushkey
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> \xf5
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: True
$ sendhttpv2peer << EOF
> command listkeys
> namespace bookmarks
> EOF
creating http peer for wire protocol version 2
sending listkeys command
s> POST /api/exp-http-v2-0001/ro/listkeys 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: 49\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\xa1InamespaceIbookmarksDnameHlistkeys
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> 35\r\n
s> -\x00\x00\x01\x00\x02\x001
s> \xa1A@X(426bada5c67598ca65036d57d9e4b64b0c1ce7a0
s> \r\n
received frame(size=45; 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: {
b'@': b'426bada5c67598ca65036d57d9e4b64b0c1ce7a0'
}
$ cat error.log