Re: [Xen-devel] [PATCH V4] xen/arm: domain_build: allocate lowmem for dom0 as much as possible

[Andrii Anisov <andrii.anisov@xxxxxxxxx>]

> Could you define unacceptable performance drop? Have you tried to measure
> what would be the impact?

> I know it can be bad, depending on the class of protocols. I think that
> if numbers were provided to demonstrate that bounce buffers (the swiotlb
> in Linux) are too slow for a given use case

Unfortunately I could not come up with exact requirements numbers.
Introducing another memcpy (what bouncing buffer approach does) for
block or network IO would not only reduce the operation performance
but also increase the overall system load.
All what we does for any of our PV driver solutions is avoiding data
copying inside FE-BE pair in order to increase performance, reduce
latency and system load.

Sincerely,
Andrii Anisov.

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