[PATCH v1 00/17] Provide a new two step DMA mapping API

[Leon Romanovsky]

On Thu, Oct 31, 2024 at 09:34:50AM +0100, Christoph Hellwig wrote:
> On Wed, Oct 30, 2024 at 07:44:13PM -0600, Jens Axboe wrote:
> > On Christoph's request, I tested this series last week and saw some
> > pretty significant performance regressions on my box. I don't know what
> > the status is in terms of that, just want to make sure something like
> > this doesn't get merged until that is both fully understood and sorted
> > out.

This series is a subset of the series you tested and doesn't include the
block layer changes which most likely were the cause of the performance
regression.

This is why I separated the block layer changes from the rest of the series
and marked them as RFC.

The current patch set is viable for HMM and VFIO. Can you please retest
only this series and leave the block layer changes for later till Christoph
finds the answer for the performance regression?

Thanks

> 
> Working on it, but I have way too many things going on at once.  Note
> that the weird thing about your setup was that we apparently dropped into
> the slow path, which still puzzles me.  But I should probably also look
> into making that path a little less slow.
> 
>