ESP32 SPIFFS incredibly slow?

[arnolde]

I just tested the SPIFFS example on an ESP32 in platformio.
I made the following changes:

• add function declarations before setup() (required by compiler)
• change serial speed to 115200
  Then the example ran without further changes. But I was surprised to see that the insert operations take several seconds (!) with the unchanged TABLE_SIZE 8192 and a record count of 34 (after adding the new ones).
  I added esp_timer_get_time() (=uptime in µs) to the insertOneRecord function and got this output, see the 20th insert took about 3 full seconds.
  Is this normal/expected? I would not have expected more than a few ms even for a "slow" operation of this magnitude.

Creating table... DONE
Record Limit: 1022
Record Count: 0
Creating Records... DONE
Record Count: 10
Recno: 1 ID: 1 Temp: 55
Recno: 2 ID: 2 Temp: 116
Recno: 3 ID: 3 Temp: 113
Recno: 4 ID: 4 Temp: 66
Recno: 5 ID: 5 Temp: 78
Recno: 6 ID: 6 Temp: 32
Recno: 7 ID: 7 Temp: 57
Recno: 8 ID: 8 Temp: 94
Recno: 9 ID: 9 Temp: 42
Recno: 10 ID: 10 Temp: 32
Deleting recno: 5
Record Count: 9
Recno: 1 ID: 1 Temp: 55
Recno: 2 ID: 2 Temp: 116
Recno: 3 ID: 3 Temp: 113
Recno: 4 ID: 4 Temp: 66
Recno: 5 ID: 6 Temp: 32
Recno: 6 ID: 7 Temp: 57
Recno: 7 ID: 8 Temp: 94
Recno: 8 ID: 9 Temp: 42
Recno: 9 ID: 10 Temp: 32
Appending record... DONE
Record Count: 10
Recno: 1 ID: 1 Temp: 55
Recno: 2 ID: 2 Temp: 116
Recno: 3 ID: 3 Temp: 113
Recno: 4 ID: 4 Temp: 66
Recno: 5 ID: 6 Temp: 32
Recno: 6 ID: 7 Temp: 57
Recno: 7 ID: 8 Temp: 94
Recno: 8 ID: 9 Temp: 42
Recno: 9 ID: 10 Temp: 32
Recno: 10 ID: 11 Temp: 68
6681740 Inserting record at recno: 5...
7775880 DONE
Record Count: 11
Recno: 1 ID: 1 Temp: 55
Recno: 2 ID: 2 Temp: 116
Recno: 3 ID: 3 Temp: 113
Recno: 4 ID: 4 Temp: 66
Recno: 5 ID: 5 Temp: 69
Recno: 6 ID: 6 Temp: 32
Recno: 7 ID: 7 Temp: 57
Recno: 8 ID: 8 Temp: 94
Recno: 9 ID: 9 Temp: 42
Recno: 10 ID: 10 Temp: 32
Recno: 11 ID: 11 Temp: 68
Updating record at recno: 10... DONE
Recno: 1 ID: 1 Temp: 55
Recno: 2 ID: 2 Temp: 116
Recno: 3 ID: 3 Temp: 113
Recno: 4 ID: 4 Temp: 66
Recno: 5 ID: 5 Temp: 69
Recno: 6 ID: 6 Temp: 32
Recno: 7 ID: 7 Temp: 57
Recno: 8 ID: 8 Temp: 94
Recno: 9 ID: 9 Temp: 42
Recno: 10 ID: 1234 Temp: 4321
Recno: 11 ID: 11 Temp: 68
Record Count: 11
Truncating table... DONE
Use insertRec() and deleteRec() carefully, they can be slow
Record Count: 0
8158189 Inserting record at recno: 1...
8499716 DONE
8499863 Inserting record at recno: 1...
9065511 DONE
9065680 Inserting record at recno: 1...
9675683 DONE
9675860 Inserting record at recno: 1...
10381244 DONE
10381413 Inserting record at recno: 1...
11382561 DONE
11382731 Inserting record at recno: 1...
12412779 DONE
12412955 Inserting record at recno: 1...
13678041 DONE
13678211 Inserting record at recno: 1...
15048959 DONE
15049129 Inserting record at recno: 1...
16455694 DONE
16455872 Inserting record at recno: 1...
18087719 DONE
18087896 Inserting record at recno: 1...
19854274 DONE
19854444 Inserting record at recno: 1...
21619922 DONE
21620091 Inserting record at recno: 1...
23594314 DONE
23594484 Inserting record at recno: 1...
25602773 DONE
25602947 Inserting record at recno: 1...
27833130 DONE
27833300 Inserting record at recno: 1...
30171755 DONE
30171933 Inserting record at recno: 1...
32538511 DONE
32538681 Inserting record at recno: 1...
35130074 DONE
35130244 Inserting record at recno: 1...
37841720 DONE
37841896 Inserting record at recno: 1...
40969952 DONE
Record Count: 20
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Deleting recno: 1
Record Count: 0