lock-free trx_sys get performance regression cause by lf_find and ut_delay

Hello, guys

we have port the lock-free trx-sys, however I find that the oltp_read_write case get too much performance regression compare with non-lock-free version..
Especially when the isolation-level is "read-committed", lock-free trx-sys get about 40% performance regression.
I guess Mariadb has the same problem..

This is my sysbench test configure
bench_type=oltp_read_write;
threads=560
tables=8
table_size=500000

there is another issue that relate to the lock-free trx_sys
https://jira.mariadb.org/browse/MDEV-20630?filter=-2

blow is the sysbench result:
you can find that the lockfree trx-sys vs non-lockfree trx-sys is
tps 13405.28 vs 20095.02
qps 268105.66 vs 401900.40

lockfree trx-sys : isolation-level

read-committed

SQL statistics:
queries performed:
read: 33803098
write: 9658028
other: 4829014
total: 48290140
transactions: 2414507 (13405.28 per sec.)
queries: 48290140 (268105.66 per sec.)
ignored errors: 0 (0.00 per sec.)
reconnects: 0 (0.00 per sec.)

General statistics:
total time: 180.1141s
total number of events: 2414507

Latency (ms):
min: 2.96
avg: 41.75
max: 4487.73
95th percentile: 92.42
sum: 100805088.64

Threads fairness:
events (avg/stddev): 4311.6196/167.34
execution time (avg/stddev): 180.0091/0.01

non-lockfree: read-committed

SQL statistics:
queries performed:
read: 50672678
write: 14477908
other: 7238954
total: 72389540
transactions: 3619477 (20095.02 per sec.)
queries: 72389540 (401900.40 per sec.)
ignored errors: 0 (0.00 per sec.)
reconnects: 0 (0.00 per sec.)

General statistics:
total time: 180.1161s
total number of events: 3619477

Latency (ms):
min: 2.47
avg: 27.85
max: 198.43
95th percentile: 52.89
sum: 100798260.68

Threads fairness:
events (avg/stddev): 6463.3518/107.19
execution time (avg/stddev): 179.9969/0.01