On Mar 15, 2021, at 11:37 AM, Harshad Shirwadkar [off-list ref] wrote:

Created a highly fragmented disk of size 65TB. The disk had no
contiguous 2M regions. Following command was run consecutively for 3
times:

time dd if=/dev/urandom of=file bs=2M count=10

Here are the results with and without cr 0/1 optimizations:

|---------+------------------------------+---------------------------|
|         | Without CR 0/1 Optimizations | With CR 0/1 Optimizations |
|---------+------------------------------+---------------------------|
| 1st run | 5m1.871s                     | 2m47.642s                 |
| 2nd run | 2m28.390s                    | 0m0.611s                  |
| 3rd run | 2m26.530s                    | 0m1.255s                  |
|---------+------------------------------+---------------------------|

IMHO, it would be useful to include this into the 5/6 patch commit
message, so that it is available with the patch in the future.
That will show the workload and basic test environment used to
justify this change, in case there are problems/changes in the future.

Cheers, Andreas