cache: stop requeuing negative entries on the hot list
Turns out it does not improve hit ratio, but it does come with a cost
induces stemming from dirtying hit entries.
Sample result: hit counts of evicted entries after 2 buildworlds
before:
value ------------- Distribution ------------- count
-1 | 0
0 |@@@@@@@@@@@@@@@@@@@@@@@@@ 180865
1 |@@@@@@@ 49150
2 |@@@ 19067
4 |@ 9825
8 |@ 7340
16 |@ 5952
32 |@ 5243
64 |@ 4446
128 | 3556
256 | 3035
512 | 1705
1024 | 1078
2048 | 365
4096 | 95
8192 | 34
16384 | 26
32768 | 23
65536 | 8
131072 | 6
262144 | 0after:
value ------------- Distribution ------------- count
-1 | 0
0 |@@@@@@@@@@@@@@@@@@@@@@@@@ 184004
1 |@@@@@@ 47577
2 |@@@ 19446
4 |@ 10093
8 |@ 7470
16 |@ 5544
32 |@ 5475
64 |@ 5011
128 | 3451
256 | 3002
512 | 1729
1024 | 1086
2048 | 363
4096 | 86
8192 | 26
16384 | 25
32768 | 24
65536 | 7
131072 | 5
262144 | 0Sponsored by: The FreeBSD Foundation