Fills memtable with rows and a tombstone which deletes all rows which
are already in cache.
Similar to raft log workload, but more extreme.
With -c1 -m4G, observed really bad performance:
update: 1711.976196 [ms], preemption: {count: 22603, 99%: 0.943127 [ms], max: 1494.571776 [ms]}, cache: 2148/2906 [MB], alloc/comp: 1334/869 [MB] (amp: 0.651), pr/me/dr 1062186/0/1062187
cache: 2148/2906 [MB], memtable: 738/1024 [MB], alloc/comp: 993/0 [MB] (amp: 0.000)
Which means that max reactor stall during cache update was 1.5 [s]
0.7 GB memtables. 2.1 GB in cache.
721434054b