[PATCH v5] erofs: add per-cpu threads for decompression as an option

[Gao Xiang]

Hi Sandeep,

On 2023/2/28 12:47, Sandeep Dhavale via Linux-erofs wrote:
> Hi all,
> I completed the tests and the results are consistent with
> our previous observation. We can see that removing WQ_UNBOUND
> helps but the scheduling latency by using high priority per cpu
> kthreads is even lower. Below is the table.
> 
> |---------------------+-------+-------+------+-------|
> | Table               | avg   | med   | min  | max   |
> |---------------------+-------+-------+------+-------|
> | Default erofs       | 19323 | 19758 | 3986 | 35051 |
> |---------------------+-------+-------+------+-------|
> | !WQ_UNBOUND         | 11202 | 10798 | 3493 | 19822 |
> |---------------------+-------+-------+------+-------|
> | hipri pcpu kthreads | 7182  | 7017  | 2463 | 12300 |
> |---------------------+-------+-------+------+-------|

May I ask did it test with different setup since the test results
in the original commit message are:

+-------------------------+-----------+----------------+---------+
|                         | workqueue | kthread_worker |  diff   |
+-------------------------+-----------+----------------+---------+
| Average (us)            |     15253 |           2914 | -80.89% |
| Median (us)             |     14001 |           2912 | -79.20% |
| Minimum (us)            |      3117 |           1027 | -67.05% |
| Maximum (us)            |     30170 |           3805 | -87.39% |
| Standard deviation (us) |      7166 |            359 |         |
+-------------------------+-----------+----------------+---------+

Otherwise it looks good to me for now, hopefully helpful to Android
users.

Thanks,
Gao Xiang

> 
> 
> Thanks,
> Sandeep.