Re: [PATCH V3 4/4] MdeModulePkg EhciDxe: Use common buffer for AsyncInterruptTransfer

[Leif Lindholm <leif.lindholm@linaro.org>]

On Thu, Nov 01, 2018 at 09:12:04AM +0800, Zeng, Star wrote:
> > > I believe the performance data really depends on
> > > 1. How many AsyncInterruptTransfer handlers (the number of USB keyboard
> > > and/or USB bluetooth keyboard?)
> > > 2. Data size (for flushing data from PCI controller specific address to
> > > mapped system memory address *in original code*)
> > > 3. The performance of IoMmu->SetAttribute (for example, the SetAttribute
> > > operation on Intel VTd engine caused by the unmap and map for flushing data
> > > *in original code*, the SetAttribute operation on IntelVTd engine will
> > > involve FlushPageTableMemory, InvalidatePageEntry and etc)
> > > 
> > > > On an unrelated note to the concerns above:
> > > > Why has a fundamental change to the behaviour of one of the industry
> > > > standard drivers been pushed at the very end of the stable cycle?
> > > 
> > > We thought it was a simple improvement but not fundamental change before
> > > Eugene and Ard raised the concern.
> > 
> > Understood.
> 
> Thanks. :)
> 
> > 
> > However, as it is changing the memory management behaviour of a core
> > driver, I think it automatically qualifies as something that should
> > only go in the week after a stable tag.
> > 
> > We will need to have a closer look at the non-coherent case when Ard
> > gets back (Monday).
> 
> You mean Ard is on vacation and will be back next Monday.

Yes.

> > If this version causes issues with non-coherent systems, we will need
> > to revert it before the stable tag. We would then need to look into
> > the best way to deal with the performance issues quoted above.
> 
> I am glad to revert it if it has side effect. Is it possible someone could
> have a quick check?

Ard could. It would take me much longer :)
Which is why I would prefer to wait until next week.

Regards,

Leif