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
$ cat >> $HGRCPATH << EOF
> [extensions]
> fastannotate=
> EOF
$ hg init repo
$ cd repo
$ for i in 0 1 2 3 4; do
> echo $i >> a
> echo $i >> b
> hg commit -A -m $i a b
> done
use the "debugbuildannotatecache" command to build annotate cache at rev 0
$ hg debugbuildannotatecache --debug --config fastannotate.mainbranch=0
fastannotate: a: 1 new changesets in the main branch
fastannotate: b: 1 new changesets in the main branch
"debugbuildannotatecache" should work with broken cache (and other files would
be built without being affected). note: linelog being broken is only noticed
when we try to append to it.
$ echo 'CORRUPT!' >> .hg/fastannotate/default/a.m
$ hg debugbuildannotatecache --debug --config fastannotate.mainbranch=1
fastannotate: a: rebuilding broken cache
fastannotate: a: 2 new changesets in the main branch
fastannotate: b: 1 new changesets in the main branch
$ echo 'CANNOT REUSE!' > .hg/fastannotate/default/a.l
$ hg debugbuildannotatecache --debug --config fastannotate.mainbranch=2
fastannotate: a: rebuilding broken cache
fastannotate: a: 3 new changesets in the main branch
fastannotate: b: 1 new changesets in the main branch
$ rm .hg/fastannotate/default/a.m
$ hg debugbuildannotatecache --debug --config fastannotate.mainbranch=3
fastannotate: a: rebuilding broken cache
fastannotate: a: 4 new changesets in the main branch
fastannotate: b: 1 new changesets in the main branch
$ rm .hg/fastannotate/default/a.l
$ hg debugbuildannotatecache --debug --config fastannotate.mainbranch=3
$ hg debugbuildannotatecache --debug --config fastannotate.mainbranch=4
fastannotate: a: rebuilding broken cache
fastannotate: a: 5 new changesets in the main branch
fastannotate: b: 1 new changesets in the main branch
"fastannotate" should deal with file corruption as well
$ rm -rf .hg/fastannotate
$ hg fastannotate --debug -r 0 a
fastannotate: a: 1 new changesets in the main branch
0: 0
$ echo 'CORRUPT!' >> .hg/fastannotate/default/a.m
$ hg fastannotate --debug -r 0 a
fastannotate: a: cache broken and deleted
fastannotate: a: 1 new changesets in the main branch
0: 0
$ echo 'CORRUPT!' > .hg/fastannotate/default/a.l
$ hg fastannotate --debug -r 1 a
fastannotate: a: cache broken and deleted
fastannotate: a: 2 new changesets in the main branch
0: 0
1: 1
$ rm .hg/fastannotate/default/a.l
$ hg fastannotate --debug -r 1 a
fastannotate: a: using fast path (resolved fctx: True)
fastannotate: a: cache broken and deleted
fastannotate: a: 2 new changesets in the main branch
0: 0
1: 1
$ rm .hg/fastannotate/default/a.m
$ hg fastannotate --debug -r 2 a
fastannotate: a: cache broken and deleted
fastannotate: a: 3 new changesets in the main branch
0: 0
1: 1
2: 2