...before 128

          idx          | level | l_item | blkno | btpo_prev | btpo_next | btpo_flags | type | live_items | dead_items | avg_item_size | page_size | free_size |         highkey         
-—---------------------+-------+--------+-------+-----------+-----------+------------+------+------------+------------+---------------+-----------+-----------+-------------------------
 pgbench_accounts_pkey |     2 |      1 |   290 |         0 |         0 |          2 | r    |         10 |          0 |            15 |      8192 |      7956 | 
 pgbench_accounts_pkey |     1 |      1 |     3 |         0 |       289 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 09 96 01 00 00 00 00 00
 pgbench_accounts_pkey |     1 |      2 |   289 |         3 |       575 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 11 2c 03 00 00 00 00 00
 pgbench_accounts_pkey |     1 |      3 |   575 |       289 |       860 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 19 c2 04 00 00 00 00 00
 pgbench_accounts_pkey |     1 |      4 |   860 |       575 |      1145 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 21 58 06 00 00 00 00 00
 pgbench_accounts_pkey |     1 |      5 |  1145 |       860 |      1430 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 29 ee 07 00 00 00 00 00
 pgbench_accounts_pkey |     1 |      6 |  1430 |      1145 |      1715 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 31 84 09 00 00 00 00 00
 pgbench_accounts_pkey |     1 |      7 |  1715 |      1430 |      2000 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 39 1a 0b 00 00 00 00 00
 pgbench_accounts_pkey |     1 |      8 |  2000 |      1715 |      2285 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 41 b0 0c 00 00 00 00 00
 pgbench_accounts_pkey |     1 |      9 |  2285 |      2000 |      2570 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 49 46 0e 00 00 00 00 00
 pgbench_accounts_pkey |     1 |     10 |  2570 |      2285 |         0 |          0 | i    |        177 |          0 |            15 |      8192 |      4616 | 
(11 rows)

latency average = 1.375 ms
tps = 93085.250384 (including connections establishing)
tps = 93125.724773 (excluding connections establishing)
SQL script 1: /home/nglukhov/ycsb_read_zipf.sql
 - weight: 1 (targets 50.0% of total)
 - 2782999 transactions (49.8% of total, tps = 46364.447705)
 - latency average = 0.131 ms
 - latency stddev = 0.087 ms
SQL script 2: /home/nglukhov/ycsb_update_zipf.sql
 - weight: 1 (targets 50.0% of total)
 - 2780197 transactions (49.8% of total, tps = 46317.766703)
 - latency average = 2.630 ms
 - latency stddev = 14.092 ms

after 128

          idx          | level | l_item | blkno | btpo_prev | btpo_next | btpo_flags | type | live_items | dead_items | avg_item_size | page_size | free_size |         highkey         
—----------------------+-------+--------+-------+-----------+-----------+------------+------+------------+------------+---------------+-----------+-----------+-------------------------
 pgbench_accounts_pkey |     2 |      1 |   290 |         0 |         0 |          2 | r    |         10 |          0 |            15 |      8192 |      7956 | 
 pgbench_accounts_pkey |     1 |      1 |     3 |         0 |       289 |          0 | i    |        353 |          0 |            15 |      8192 |      1096 | 09 96 01 00 00 00 00 00
 pgbench_accounts_pkey |     1 |      2 |   289 |         3 |       575 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 11 2c 03 00 00 00 00 00
 pgbench_accounts_pkey |     1 |      3 |   575 |       289 |       860 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 19 c2 04 00 00 00 00 00
 pgbench_accounts_pkey |     1 |      4 |   860 |       575 |      1145 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 21 58 06 00 00 00 00 00
 pgbench_accounts_pkey |     1 |      5 |  1145 |       860 |      1430 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 29 ee 07 00 00 00 00 00
 pgbench_accounts_pkey |     1 |      6 |  1430 |      1145 |      1715 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 31 84 09 00 00 00 00 00
 pgbench_accounts_pkey |     1 |      7 |  1715 |      1430 |      2000 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 39 1a 0b 00 00 00 00 00
 pgbench_accounts_pkey |     1 |      8 |  2000 |      1715 |      2285 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 41 b0 0c 00 00 00 00 00
 pgbench_accounts_pkey |     1 |      9 |  2285 |      2000 |      2570 |          0 | i    |        285 |          0 |            15 |      8192 |      2456 | 49 46 0e 00 00 00 00 00
 pgbench_accounts_pkey |     1 |     10 |  2570 |      2285 |         0 |          0 | i    |        177 |          0 |            15 |      8192 |      4616 | 
(11 rows)