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
$ hg init
$ echo foo > bar
$ hg commit -Am default
adding bar
$ hg up -r null
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg branch mine
marked working directory as branch mine
(branches are permanent and global, did you want a bookmark?)
$ echo hello > world
$ hg commit -Am hello
adding world
$ hg up -r null
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg branch other
marked working directory as branch other
$ echo good > bye
$ hg commit -Am other
adding bye
$ hg up -r mine
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg clone -U -u . .#other ../b -r 0 -r 1 -r 2 -b other
abort: cannot specify both --noupdate and --updaterev
[255]
$ hg clone -U .#other ../b -r 0 -r 1 -r 2 -b other
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 3 files (+2 heads)
new changesets 8c68ee086fd0:fcc393352796
$ rm -rf ../b
$ hg clone -u . .#other ../b -r 0 -r 1 -r 2 -b other
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 3 files (+2 heads)
new changesets 8c68ee086fd0:fcc393352796
updating to branch mine
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ rm -rf ../b
$ hg clone -u 0 .#other ../b -r 0 -r 1 -r 2 -b other
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 3 files (+2 heads)
new changesets 8c68ee086fd0:fcc393352796
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ rm -rf ../b
$ hg clone -u 1 .#other ../b -r 0 -r 1 -r 2 -b other
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 3 files (+2 heads)
new changesets 8c68ee086fd0:fcc393352796
updating to branch mine
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ rm -rf ../b
$ hg clone -u 2 .#other ../b -r 0 -r 1 -r 2 -b other
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 3 files (+2 heads)
new changesets 8c68ee086fd0:fcc393352796
updating to branch other
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ rm -rf ../b
Test -r mine ... mine is ignored:
$ hg clone -u 2 .#other ../b -r mine -r 0 -r 1 -r 2 -b other
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 3 files (+2 heads)
new changesets 8c68ee086fd0:fcc393352796
updating to branch other
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ rm -rf ../b
$ hg clone .#other ../b -b default -b mine
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 3 files (+2 heads)
new changesets 8c68ee086fd0:fcc393352796
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ rm -rf ../b
$ hg clone .#other ../b
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
new changesets fcc393352796
updating to branch other
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ rm -rf ../b
$ hg clone -U . ../c -r 1 -r 2 > /dev/null
$ hg clone ../c ../b
updating to branch other
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ rm -rf ../b ../c