Re: [PATCH 2/2] ufs: don't use the fair tag sharings

From: Bart Van Assche
Date: Thu May 11 2023 - 11:38:11 EST

On 5/11/23 08:34, Christoph Hellwig wrote:
On Tue, May 09, 2023 at 02:52:30PM +0800, Ed Tsai wrote:
The tags allocation is limited by the fair sharing algorithm. It hurts
the performance for UFS devices, because the queue depth of general I/O
is reduced by half once the UFS send a control command.

But it is there for a reason. You completely fail to explain why you
think your change is safe, and also why you did not try to even explain
where the overhead is and how else you tried to mitigate it.

Hi Christoph,

For which devices is the fair sharing algorithm useful? As far as I know the legacy block layer did not have an equivalent of the fair sharing algorithm and I'm not aware of any complaints about the legacy block layer regarding to fairness. This is why I proposed in January to remove the fair sharing code entirely. See also