[dm-devel] [git pull] device mapper changes for 5.9

[Linus Torvalds]

On Fri, Aug 7, 2020 at 9:03 AM Mike Snitzer <snitzer at redhat.com> wrote:
>
> - DM crypt improvement to optionally avoid async processing via
>   workqueues for reads and/or writes -- via "no_read_workqueue" and
>   "no_write_workqueue" features.  This more direct IO processing
>   improves latency and throughput with faster storage.  Avoiding
>   workqueue IO submission for writes (DM_CRYPT_NO_WRITE_WORKQUEUE) is
>   a requirement for adding zoned block device support to DM crypt.

Is there a reason the async workqueue isn't removed entirely if it's not a win?

Or at least made to not be the default.

Now it seems to be just optionally disabled, which seems the wrong way
around to me.

I do not believe async crypto has ever worked or been worth it.
Off-loaded crypto in the IO path, yes. Async using a workqueue? Naah.

Or do I misunderstand?

               Linus