Messages in this thread | | | Date | Wed, 17 May 2023 13:27:48 +0200 | From | Petr Tesařík <> | Subject | Re: [PATCH v2 RESEND 4/7] swiotlb: Dynamically allocated bounce buffers |
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On Wed, 17 May 2023 08:35:10 +0200 Petr Tesařík <petr@tesarici.cz> wrote:
>[...] > Anyway, my greatest objection to allocating additional swiotlb chunks is > that _all_ of them must be searched to determine that the physical > address does _not_ belong to a swiotlb, incurring performance penalty
I thought about this part again, and I overlooked one option. We can track only the _active_ swiotlbs for each device. If a device never needs a swiotlb, there is no active swiotlb, and is_swiotlb_buffer() short-circuits to false. This should avoid all collateral damage to innocent devices.
We would also maintain a (global) list of all allocated swiotlbs, used by swiotlb_map() to find free slots and add the respective swiotlb to the per-device active list.
One potential advantage is that we could use mapping size and alignment to choose a swiotlb cleverly and minimize internal fragmentation...
OK, I'm dreaming. Let's agree on the general approach first.
Petr T
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