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=
> [fastannotate]
> mainbranch=main
> EOF
$ hg init repo
$ cd repo
add or rename files on top of the master branch
$ echo a1 > a
$ echo b1 > b
$ hg commit -qAm 1
$ hg bookmark -i main
$ hg fastannotate --debug -nf b
fastannotate: b: 1 new changesets in the main branch
0 b: b1
$ hg fastannotate --debug -nf a
fastannotate: a: 1 new changesets in the main branch
0 a: a1
$ echo a2 >> a
$ cat > b << EOF
> b0
> b1
> EOF
$ hg mv a t
$ hg mv b a
$ hg mv t b
$ hg commit -m 'swap names'
existing linelogs are not helpful with such renames in side branches
$ hg fastannotate --debug -nf a
fastannotate: a: linelog cannot help in annotating this revision
1 a: b0
0 b: b1
$ hg fastannotate --debug -nf b
fastannotate: b: linelog cannot help in annotating this revision
0 a: a1
1 b: a2
move main branch forward, rebuild should happen
$ hg bookmark -i main -r . -q
$ hg fastannotate --debug -nf b
fastannotate: b: cache broken and deleted
fastannotate: b: 2 new changesets in the main branch
0 a: a1
1 b: a2
$ hg fastannotate --debug -nf b
fastannotate: b: using fast path (resolved fctx: True)
0 a: a1
1 b: a2
for rev 0, the existing linelog is still useful for a, but not for b
$ hg fastannotate --debug -nf a -r 0
fastannotate: a: using fast path (resolved fctx: True)
0 a: a1
$ hg fastannotate --debug -nf b -r 0
fastannotate: b: linelog cannot help in annotating this revision
0 b: b1
a rebuild can also be triggered if "the main branch last time" mismatches
$ echo a3 >> a
$ hg commit -m a3
$ cat >> b << EOF
> b3
> b4
> EOF
$ hg commit -m b4
$ hg bookmark -i main -q
$ hg fastannotate --debug -nf a
fastannotate: a: cache broken and deleted
fastannotate: a: 3 new changesets in the main branch
1 a: b0
0 b: b1
2 a: a3
$ hg fastannotate --debug -nf a
fastannotate: a: using fast path (resolved fctx: True)
1 a: b0
0 b: b1
2 a: a3
linelog can be updated without being helpful
$ hg mv a t
$ hg mv b a
$ hg mv t b
$ hg commit -m 'swap names again'
$ hg fastannotate --debug -nf b
fastannotate: b: 1 new changesets in the main branch
1 a: b0
0 b: b1
2 a: a3
$ hg fastannotate --debug -nf b
fastannotate: b: linelog cannot help in annotating this revision
1 a: b0
0 b: b1
2 a: a3
move main branch forward again, rebuilds are one-time
$ hg bookmark -i main -q
$ hg fastannotate --debug -nf a
fastannotate: a: cache broken and deleted
fastannotate: a: 4 new changesets in the main branch
0 a: a1
1 b: a2
3 b: b3
3 b: b4
$ hg fastannotate --debug -nf b
fastannotate: b: cache broken and deleted
fastannotate: b: 4 new changesets in the main branch
1 a: b0
0 b: b1
2 a: a3
$ hg fastannotate --debug -nf a
fastannotate: a: using fast path (resolved fctx: True)
0 a: a1
1 b: a2
3 b: b3
3 b: b4
$ hg fastannotate --debug -nf b
fastannotate: b: using fast path (resolved fctx: True)
1 a: b0
0 b: b1
2 a: a3
list changeset hashes to improve readability
$ hg log -T '{rev}:{node}\n'
4:980e1ab8c516350172928fba95b49ede3b643dca
3:14e123fedad9f491f5dde0beca2a767625a0a93a
2:96495c41e4c12218766f78cdf244e768d7718b0f
1:35c2b781234c994896aba36bd3245d3104e023df
0:653e95416ebb5dbcc25bbc7f75568c9e01f7bd2f
annotate a revision not in the linelog. linelog cannot be used, but does not get rebuilt either
$ hg fastannotate --debug -nf a -r 96495c41e4c12218766f78cdf244e768d7718b0f
fastannotate: a: linelog cannot help in annotating this revision
1 a: b0
0 b: b1
2 a: a3
$ hg fastannotate --debug -nf a -r 2
fastannotate: a: linelog cannot help in annotating this revision
1 a: b0
0 b: b1
2 a: a3
$ hg fastannotate --debug -nf a -r .
fastannotate: a: using fast path (resolved fctx: True)
0 a: a1
1 b: a2
3 b: b3
3 b: b4
annotate an ancient revision where the path matches. linelog can be used
$ hg fastannotate --debug -nf a -r 0
fastannotate: a: using fast path (resolved fctx: True)
0 a: a1
$ hg fastannotate --debug -nf a -r 653e95416ebb5dbcc25bbc7f75568c9e01f7bd2f
fastannotate: a: using fast path (resolved fctx: False)
0 a: a1